Merge pull request #157 from vulcanize/statediff_at

(VDB-933) Backfill for storage diff transformer

cmd/composeAndExecute.go

@@ -17,10 +17,6 @@
 package cmd
 
 import (
-	"github.com/ethereum/go-ethereum/statediff"
-	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
-	"github.com/vulcanize/vulcanizedb/libraries/shared/streamer"
-	"github.com/vulcanize/vulcanizedb/pkg/fs"
 	"os"
 	"plugin"
 	syn "sync"
@@ -29,7 +25,10 @@ import (
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 
+	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/streamer"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/watcher"
+	"github.com/vulcanize/vulcanizedb/pkg/fs"
 	p2 "github.com/vulcanize/vulcanizedb/pkg/plugin"
 	"github.com/vulcanize/vulcanizedb/pkg/plugin/helpers"
 	"github.com/vulcanize/vulcanizedb/utils"
@@ -186,12 +185,11 @@ func composeAndExecute() {
 			log.Debug("fetching storage diffs from geth pub sub")
 			rpcClient, _ := getClients()
 			stateDiffStreamer := streamer.NewStateDiffStreamer(rpcClient)
-			payloadChan := make(chan statediff.Payload)
-			storageFetcher := fetcher.NewGethRPCStorageFetcher(&stateDiffStreamer, payloadChan)
+			storageFetcher := fetcher.NewGethRPCStorageFetcher(stateDiffStreamer)
 			sw := watcher.NewStorageWatcher(storageFetcher, &db)
 			sw.AddTransformers(ethStorageInitializers)
 			wg.Add(1)
-			go watchEthStorage(&sw, &wg)
+			go watchEthStorage(sw, &wg)
 		default:
 			log.Debug("fetching storage diffs from csv")
 			tailer := fs.FileTailer{Path: storageDiffsPath}
@@ -199,7 +197,7 @@ func composeAndExecute() {
 			sw := watcher.NewStorageWatcher(storageFetcher, &db)
 			sw.AddTransformers(ethStorageInitializers)
 			wg.Add(1)
-			go watchEthStorage(&sw, &wg)
+			go watchEthStorage(sw, &wg)
 		}
 	}
 

cmd/contractWatcher.go

@@ -18,13 +18,13 @@ package cmd
 
 import (
 	"fmt"
-	"github.com/vulcanize/vulcanizedb/pkg/config"
 	"time"
 
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
 
 	st "github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
+	"github.com/vulcanize/vulcanizedb/pkg/config"
 	ft "github.com/vulcanize/vulcanizedb/pkg/contract_watcher/full/transformer"
 	ht "github.com/vulcanize/vulcanizedb/pkg/contract_watcher/header/transformer"
 	"github.com/vulcanize/vulcanizedb/utils"

cmd/execute.go

@@ -18,21 +18,21 @@ package cmd
 
 import (
 	"fmt"
-	"github.com/ethereum/go-ethereum/statediff"
-	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
-	"github.com/vulcanize/vulcanizedb/libraries/shared/streamer"
-	"github.com/vulcanize/vulcanizedb/pkg/fs"
 	"plugin"
 	syn "sync"
 	"time"
 
 	log "github.com/sirupsen/logrus"
 	"github.com/spf13/cobra"
+	"github.com/spf13/viper"
 
 	"github.com/vulcanize/vulcanizedb/libraries/shared/constants"
-	storageUtils "github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/streamer"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/watcher"
+	"github.com/vulcanize/vulcanizedb/pkg/fs"
 	"github.com/vulcanize/vulcanizedb/utils"
 )
 
@@ -41,28 +41,22 @@ var executeCmd = &cobra.Command{
 	Use:   "execute",
 	Short: "executes a precomposed transformer initializer plugin",
 	Long: `This command needs a config .toml file of form:
-
 [database]
     name     = "vulcanize_public"
     hostname = "localhost"
     user     = "vulcanize"
     password = "vulcanize"
     port     = 5432
-
 [client]
     ipcPath  = "/Users/user/Library/Ethereum/geth.ipc"
-
 [exporter]
     name     = "exampleTransformerExporter"
-
 Note: If any of the plugin transformer need additional
 configuration variables include them in the .toml file as well
-
 The exporter.name is the name (without extension) of the plugin to be loaded.
 The plugin file needs to be located in the /plugins directory and this command assumes 
 the db migrations remain from when the plugin was composed. Additionally, the plugin 
 must have been composed by the same version of vulcanizedb or else it will not be compatible.
-
 Specify config location when executing the command:
 ./vulcanizedb execute --config=./environments/config_name.toml`,
 	Run: func(cmd *cobra.Command, args []string) {
@@ -128,14 +122,13 @@ func execute() {
 		switch storageDiffsSource {
 		case "geth":
 			log.Debug("fetching storage diffs from geth pub sub")
-			rpcClient, _ := getClients()
-			stateDiffStreamer := streamer.NewStateDiffStreamer(rpcClient)
-			payloadChan := make(chan statediff.Payload)
-			storageFetcher := fetcher.NewGethRPCStorageFetcher(&stateDiffStreamer, payloadChan)
+			wsClient := getWSClient()
+			stateDiffStreamer := streamer.NewStateDiffStreamer(wsClient)
+			storageFetcher := fetcher.NewGethRPCStorageFetcher(stateDiffStreamer)
 			sw := watcher.NewStorageWatcher(storageFetcher, &db)
 			sw.AddTransformers(ethStorageInitializers)
 			wg.Add(1)
-			go watchEthStorage(&sw, &wg)
+			go watchEthStorage(sw, &wg)
 		default:
 			log.Debug("fetching storage diffs from csv")
 			tailer := fs.FileTailer{Path: storageDiffsPath}
@@ -143,7 +136,7 @@ func execute() {
 			sw := watcher.NewStorageWatcher(storageFetcher, &db)
 			sw.AddTransformers(ethStorageInitializers)
 			wg.Add(1)
-			go watchEthStorage(&sw, &wg)
+			go watchEthStorage(sw, &wg)
 		}
 	}
 
@@ -186,13 +179,20 @@ func watchEthStorage(w watcher.IStorageWatcher, wg *syn.WaitGroup) {
 	defer wg.Done()
 	// Execute over the StorageTransformerInitializer set using the storage watcher
 	LogWithCommand.Info("executing storage transformers")
-	ticker := time.NewTicker(pollingInterval)
-	defer ticker.Stop()
-	for range ticker.C {
-		errs := make(chan error)
-		diffs := make(chan storageUtils.StorageDiff)
-		w.Execute(diffs, errs, queueRecheckInterval)
+	on := viper.GetBool("storageBackFill.on")
+	if on {
+		backFillStorage(w)
 	}
+	w.Execute(queueRecheckInterval, on)
+}
+
+func backFillStorage(w watcher.IStorageWatcher) {
+	rpcClient, _ := getClients()
+	// find min deployment block
+	minDeploymentBlock := constants.GetMinDeploymentBlock()
+	stateDiffFetcher := fetcher.NewStateDiffFetcher(rpcClient)
+	backFiller := storage.NewStorageBackFiller(stateDiffFetcher, storage.DefaultMaxBatchSize)
+	go w.BackFill(minDeploymentBlock, backFiller)
 }
 
 func watchEthContract(w *watcher.ContractWatcher, wg *syn.WaitGroup) {

cmd/root.go

@@ -17,6 +17,7 @@
 package cmd
 
 import (
+	"errors"
 	"fmt"
 	"strings"
 	"time"
@@ -28,6 +29,7 @@ import (
 	"github.com/spf13/viper"
 
 	"github.com/vulcanize/vulcanizedb/pkg/config"
+	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/eth"
 	"github.com/vulcanize/vulcanizedb/pkg/eth/client"
 	vRpc "github.com/vulcanize/vulcanizedb/pkg/eth/converters/rpc"
@@ -174,3 +176,15 @@ func getClients() (client.RPCClient, *ethclient.Client) {
 
 	return rpcClient, ethClient
 }
+
+func getWSClient() core.RPCClient {
+	wsRPCpath := viper.GetString("client.wsPath")
+	if wsRPCpath == "" {
+		LogWithCommand.Fatal(errors.New("getWSClient() was called but no ws rpc path is provided"))
+	}
+	wsRPCClient, dialErr := rpc.Dial(wsRPCpath)
+	if dialErr != nil {
+		LogWithCommand.Fatal(dialErr)
+	}
+	return client.NewRPCClient(wsRPCClient, wsRPCpath)
+}

documentation/custom-transformers.md

@@ -100,6 +100,7 @@ The config provides information for composing a set of transformers from externa
 
 [client]
     ipcPath  = "/Users/user/Library/Ethereum/geth.ipc"
+    wsPath   = "ws://127.0.0.1:8546"
 
 [exporter]
     home     = "github.com/vulcanize/vulcanizedb"
@@ -160,6 +161,7 @@ The config provides information for composing a set of transformers from externa
         - don't leave gaps
         - transformers with identical migrations/migration paths should share the same rank
 - Note: If any of the imported transformers need additional config variables those need to be included as well   
+- Note: If the storage transformers are processing storage diffs from geth, we need to configure the websocket endpoint `client.wsPath` for them
 
 This information is used to write and build a Go plugin which exports the configured transformers.
 These transformers are loaded onto their specified watchers and executed.
@@ -194,3 +196,17 @@ func (e exporter) Export() []interface1.EventTransformerInitializer, []interface
         }
 }
 ```
+
+### Storage backfilling
+Storage transformers stream data from a geth subscription or parity csv file where the storage diffs are produced and emitted as the
+full sync progresses. If the transformers have missed consuming a range of diffs due to lag in the startup of the processes or due to misalignment of the sync,
+we can configure our storage transformers to backfill missing diffs from a [modified archival geth client](https://github.com/vulcanize/go-ethereum/tree/statediff_at).
+
+To do so, add the following fields to the config file.
+```toml
+[storageBackFill]
+    on = false
+```
+- `on` is set to `true` to turn the backfill process on
+
+This process uses the regular `client.ipcPath` rpc path, it assumes that it is either an http or ipc path that supports the `StateDiffAt` endpoint.

libraries/shared/chunker/chunker_suite_test.go

@@ -19,10 +19,11 @@ package chunker_test
 import (
 	"testing"
 
+	"io/ioutil"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	log "github.com/sirupsen/logrus"
-	"io/ioutil"
 )
 
 func TestFactories(t *testing.T) {

libraries/shared/chunker/log_chunker.go

@@ -17,10 +17,11 @@
 package chunker
 
 import (
+	"strings"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
-	"strings"
 )
 
 type Chunker interface {

libraries/shared/constants/external.go

@@ -0,0 +1,80 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package constants
+
+import (
+	"fmt"
+	"math"
+
+	log "github.com/sirupsen/logrus"
+	"github.com/spf13/viper"
+)
+
+var initialized = false
+
+func initConfig() {
+	if initialized {
+		return
+	}
+
+	if err := viper.ReadInConfig(); err == nil {
+		log.Info("Using config file:", viper.ConfigFileUsed())
+	} else {
+		panic(fmt.Sprintf("Could not find environment file: %v", err))
+	}
+	initialized = true
+}
+
+// GetMinDeploymentBlock gets the minimum deployment block for multiple contracts from config
+func GetMinDeploymentBlock() uint64 {
+	initConfig()
+	contractNames := getContractNames()
+	if len(contractNames) < 1 {
+		log.Fatalf("No contracts supplied")
+	}
+	minBlock := uint64(math.MaxUint64)
+	for c := range contractNames {
+		deployed := getDeploymentBlock(c)
+		if deployed < minBlock {
+			minBlock = deployed
+		}
+	}
+	return minBlock
+}
+
+func getContractNames() map[string]bool {
+	transformerNames := viper.GetStringSlice("exporter.transformerNames")
+	contractNames := make(map[string]bool)
+	for _, transformerName := range transformerNames {
+		configKey := "exporter." + transformerName + ".contracts"
+		names := viper.GetStringSlice(configKey)
+		for _, name := range names {
+			contractNames[name] = true
+		}
+	}
+	return contractNames
+}
+
+func getDeploymentBlock(contractName string) uint64 {
+	configKey := "contract." + contractName + ".deployed"
+	value := viper.GetInt64(configKey)
+	if value < 0 {
+		log.Infof("No deployment block configured for contract \"%v\", defaulting to 0.", contractName)
+		return 0
+	}
+	return uint64(value)
+}

libraries/shared/factories/event/factories_suite_test.go

@@ -19,10 +19,11 @@ package event_test
 import (
 	"testing"
 
+	"io/ioutil"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	log "github.com/sirupsen/logrus"
-	"io/ioutil"
 )
 
 func TestFactories(t *testing.T) {

libraries/shared/factories/event/repository.go

@@ -19,9 +19,10 @@ package event
 import (
 	"database/sql/driver"
 	"fmt"
-	"github.com/vulcanize/vulcanizedb/utils"
 	"strings"
 
+	"github.com/vulcanize/vulcanizedb/utils"
+
 	"github.com/sirupsen/logrus"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
 )

libraries/shared/factories/event/repository_test.go

@@ -18,6 +18,8 @@ package event_test
 
 import (
 	"fmt"
+	"math/big"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/factories/event"
@@ -26,7 +28,6 @@ import (
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres/repositories"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
 	"github.com/vulcanize/vulcanizedb/test_config"
-	"math/big"
 )
 
 var _ = Describe("Repository", func() {

libraries/shared/factories/event/transformer_test.go

@@ -17,6 +17,8 @@
 package event_test
 
 import (
+	"math/rand"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/factories/event"
@@ -25,7 +27,6 @@ import (
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
-	"math/rand"
 )
 
 var _ = Describe("Transformer", func() {

libraries/shared/fetcher/csv_tail_storage_fetcher.go

@@ -17,10 +17,11 @@
 package fetcher
 
 import (
+	"strings"
+
 	"github.com/sirupsen/logrus"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/pkg/fs"
-	"strings"
 )
 
 type CsvTailStorageFetcher struct {

libraries/shared/fetcher/csv_tail_storage_fetcher_test.go

@@ -18,6 +18,9 @@ package fetcher_test
 
 import (
 	"fmt"
+	"strings"
+	"time"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/hpcloud/tail"
 	. "github.com/onsi/ginkgo"
@@ -25,8 +28,6 @@ import (
 	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
-	"strings"
-	"time"
 )
 
 var _ = Describe("Csv Tail Storage Fetcher", func() {

libraries/shared/fetcher/fetcher_suite_test.go

@@ -19,10 +19,11 @@ package fetcher_test
 import (
 	"testing"
 
+	"io/ioutil"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	log "github.com/sirupsen/logrus"
-	"io/ioutil"
 )
 
 func TestFactories(t *testing.T) {

libraries/shared/fetcher/geth_rpc_storage_fetcher.go

@@ -1,42 +1,50 @@
-// Copyright 2019 Vulcanize
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
 
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 package fetcher
 
 import (
 	"fmt"
+
+	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/statediff"
 	"github.com/sirupsen/logrus"
+
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/streamer"
 )
 
+const (
+	PayloadChanBufferSize = 20000 // the max eth sub buffer size
+)
+
 type GethRPCStorageFetcher struct {
-	statediffPayloadChan chan statediff.Payload
+	StatediffPayloadChan chan statediff.Payload
 	streamer             streamer.Streamer
 }
 
-func NewGethRPCStorageFetcher(streamer streamer.Streamer, statediffPayloadChan chan statediff.Payload) GethRPCStorageFetcher {
+func NewGethRPCStorageFetcher(streamer streamer.Streamer) GethRPCStorageFetcher {
 	return GethRPCStorageFetcher{
-		statediffPayloadChan: statediffPayloadChan,
+		StatediffPayloadChan: make(chan statediff.Payload, PayloadChanBufferSize),
 		streamer:             streamer,
 	}
 }
 
 func (fetcher GethRPCStorageFetcher) FetchStorageDiffs(out chan<- utils.StorageDiff, errs chan<- error) {
-	ethStatediffPayloadChan := fetcher.statediffPayloadChan
+	ethStatediffPayloadChan := fetcher.StatediffPayloadChan
 	clientSubscription, clientSubErr := fetcher.streamer.Stream(ethStatediffPayloadChan)
 	if clientSubErr != nil {
 		errs <- clientSubErr
@@ -54,28 +62,25 @@ func (fetcher GethRPCStorageFetcher) FetchStorageDiffs(out chan<- utils.StorageD
 			errs <- decodeErr
 		}
 
-		accounts := getAccountsFromDiff(*stateDiff)
+		accounts := utils.GetAccountsFromDiff(*stateDiff)
 		logrus.Trace(fmt.Sprintf("iterating through %d accounts on stateDiff for block %d", len(accounts), stateDiff.BlockNumber))
 		for _, account := range accounts {
-			logrus.Trace(fmt.Sprintf("iterating through %d Storage values on account", len(account.Storage)))
+			logrus.Trace(fmt.Sprintf("iterating through %d Storage values on account with key %s", len(account.Storage), common.BytesToHash(account.Key).Hex()))
 			for _, storage := range account.Storage {
 				diff, formatErr := utils.FromGethStateDiff(account, stateDiff, storage)
+				if formatErr != nil {
+					logrus.Error("failed to format utils.StorageDiff from storage with key: ", common.BytesToHash(storage.Key), "from account with key: ", common.BytesToHash(account.Key))
+					errs <- formatErr
+					continue
+				}
 				logrus.Trace("adding storage diff to out channel",
 					"keccak of address: ", diff.HashedAddress.Hex(),
 					"block height: ", diff.BlockHeight,
 					"storage key: ", diff.StorageKey.Hex(),
 					"storage value: ", diff.StorageValue.Hex())
-				if formatErr != nil {
-					errs <- formatErr
-				}
 
 				out <- diff
 			}
 		}
 	}
 }
-
-func getAccountsFromDiff(stateDiff statediff.StateDiff) []statediff.AccountDiff {
-	accounts := append(stateDiff.CreatedAccounts, stateDiff.UpdatedAccounts...)
-	return append(accounts, stateDiff.DeletedAccounts...)
-}

libraries/shared/fetcher/geth_rpc_storage_fetcher_test.go

@@ -1,16 +1,18 @@
-// Copyright 2019 Vulcanize
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 package fetcher_test
 
@@ -21,6 +23,7 @@ import (
 	"github.com/ethereum/go-ethereum/statediff"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
+
 	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/test_data"
@@ -56,15 +59,13 @@ func (streamer *MockStoragediffStreamer) SetPayloads(payloads []statediff.Payloa
 
 var _ = Describe("Geth RPC Storage Fetcher", func() {
 	var streamer MockStoragediffStreamer
-	var statediffPayloadChan chan statediff.Payload
 	var statediffFetcher fetcher.GethRPCStorageFetcher
 	var storagediffChan chan utils.StorageDiff
 	var errorChan chan error
 
 	BeforeEach(func() {
 		streamer = MockStoragediffStreamer{}
-		statediffPayloadChan = make(chan statediff.Payload, 1)
-		statediffFetcher = fetcher.NewGethRPCStorageFetcher(&streamer, statediffPayloadChan)
+		statediffFetcher = fetcher.NewGethRPCStorageFetcher(&streamer)
 		storagediffChan = make(chan utils.StorageDiff)
 		errorChan = make(chan error)
 	})
@@ -88,9 +89,9 @@ var _ = Describe("Geth RPC Storage Fetcher", func() {
 
 		go statediffFetcher.FetchStorageDiffs(storagediffChan, errorChan)
 
-		streamedPayload := <-statediffPayloadChan
+		streamedPayload := <-statediffFetcher.StatediffPayloadChan
 		Expect(streamedPayload).To(Equal(test_data.MockStatediffPayload))
-		Expect(streamer.PassedPayloadChan).To(Equal(statediffPayloadChan))
+		Expect(streamer.PassedPayloadChan).To(Equal(statediffFetcher.StatediffPayloadChan))
 		close(done)
 	})
 

libraries/shared/fetcher/state_diff_fetcher.go

@@ -0,0 +1,79 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package fetcher
+
+import (
+	"fmt"
+
+	"github.com/ethereum/go-ethereum/statediff"
+
+	"github.com/vulcanize/vulcanizedb/pkg/eth/client"
+)
+
+// StateDiffFetcher is the state diff fetching interface
+type StateDiffFetcher interface {
+	FetchStateDiffsAt(blockHeights []uint64) ([]statediff.Payload, error)
+}
+
+// BatchClient is an interface to a batch-fetching geth rpc client; created to allow mock insertion
+type BatchClient interface {
+	BatchCall(batch []client.BatchElem) error
+}
+
+// stateDiffFetcher is the state diff fetching struct
+type stateDiffFetcher struct {
+	// stateDiffFetcher is thread-safe as long as the underlying client is thread-safe, since it has/modifies no other state
+	// http.Client is thread-safe
+	client BatchClient
+}
+
+const method = "statediff_stateDiffAt"
+
+// NewStateDiffFetcher returns a IStateDiffFetcher
+func NewStateDiffFetcher(bc BatchClient) StateDiffFetcher {
+	return &stateDiffFetcher{
+		client: bc,
+	}
+}
+
+// FetchStateDiffsAt fetches the statediff payloads at the given block heights
+// Calls StateDiffAt(ctx context.Context, blockNumber uint64) (*Payload, error)
+func (fetcher *stateDiffFetcher) FetchStateDiffsAt(blockHeights []uint64) ([]statediff.Payload, error) {
+	batch := make([]client.BatchElem, 0)
+	for _, height := range blockHeights {
+		batch = append(batch, client.BatchElem{
+			Method: method,
+			Args:   []interface{}{height},
+			Result: new(statediff.Payload),
+		})
+	}
+	batchErr := fetcher.client.BatchCall(batch)
+	if batchErr != nil {
+		return nil, fmt.Errorf("stateDiffFetcher err: %s", batchErr.Error())
+	}
+	results := make([]statediff.Payload, 0, len(blockHeights))
+	for _, batchElem := range batch {
+		if batchElem.Error != nil {
+			return nil, fmt.Errorf("stateDiffFetcher err: %s", batchElem.Error.Error())
+		}
+		payload, ok := batchElem.Result.(*statediff.Payload)
+		if ok {
+			results = append(results, *payload)
+		}
+	}
+	return results, nil
+}

libraries/shared/fetcher/state_diff_fetcher_test.go

@@ -0,0 +1,54 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package fetcher_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/mocks"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/test_data"
+)
+
+var _ = Describe("StateDiffFetcher", func() {
+	Describe("FetchStateDiffsAt", func() {
+		var (
+			mc               *mocks.BackFillerClient
+			stateDiffFetcher fetcher.StateDiffFetcher
+		)
+		BeforeEach(func() {
+			mc = new(mocks.BackFillerClient)
+			setDiffAtErr1 := mc.SetReturnDiffAt(test_data.BlockNumber.Uint64(), test_data.MockStatediffPayload)
+			Expect(setDiffAtErr1).ToNot(HaveOccurred())
+			setDiffAtErr2 := mc.SetReturnDiffAt(test_data.BlockNumber2.Uint64(), test_data.MockStatediffPayload2)
+			Expect(setDiffAtErr2).ToNot(HaveOccurred())
+			stateDiffFetcher = fetcher.NewStateDiffFetcher(mc)
+		})
+		It("Batch calls statediff_stateDiffAt", func() {
+			blockHeights := []uint64{
+				test_data.BlockNumber.Uint64(),
+				test_data.BlockNumber2.Uint64(),
+			}
+			stateDiffPayloads, fetchErr := stateDiffFetcher.FetchStateDiffsAt(blockHeights)
+			Expect(fetchErr).ToNot(HaveOccurred())
+			Expect(len(stateDiffPayloads)).To(Equal(2))
+			Expect(stateDiffPayloads[0]).To(Equal(test_data.MockStatediffPayload))
+			Expect(stateDiffPayloads[1]).To(Equal(test_data.MockStatediffPayload2))
+		})
+	})
+})

libraries/shared/logs/delegator.go

@@ -18,6 +18,7 @@ package logs
 
 import (
 	"errors"
+
 	"github.com/sirupsen/logrus"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/chunker"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"

libraries/shared/logs/delegator_test.go

@@ -17,6 +17,8 @@
 package logs_test
 
 import (
+	"strings"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	. "github.com/onsi/ginkgo"
@@ -27,7 +29,6 @@ import (
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
-	"strings"
 )
 
 var _ = Describe("Log delegator", func() {

libraries/shared/logs/extractor.go

@@ -18,6 +18,7 @@ package logs
 
 import (
 	"errors"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/sirupsen/logrus"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/constants"

libraries/shared/logs/extractor_test.go

@@ -17,6 +17,8 @@
 package logs_test
 
 import (
+	"math/rand"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	. "github.com/onsi/ginkgo"
@@ -27,7 +29,6 @@ import (
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
-	"math/rand"
 )
 
 var _ = Describe("Log extractor", func() {

libraries/shared/logs/logs_suite_test.go

@@ -17,10 +17,11 @@
 package logs_test
 
 import (
-	"github.com/sirupsen/logrus"
 	"io/ioutil"
 	"testing"
 
+	"github.com/sirupsen/logrus"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )

libraries/shared/mocks/backfiller.go

@@ -0,0 +1,58 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package mocks
+
+import (
+	"errors"
+
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+)
+
+// BackFiller mock for tests
+type BackFiller struct {
+	StorageDiffsToReturn []utils.StorageDiff
+	BackFillErrs         []error
+	PassedEndingBlock    uint64
+}
+
+// SetStorageDiffsToReturn for tests
+func (backFiller *BackFiller) SetStorageDiffsToReturn(diffs []utils.StorageDiff) {
+	backFiller.StorageDiffsToReturn = diffs
+}
+
+// BackFill mock method
+func (backFiller *BackFiller) BackFill(startingBlock, endingBlock uint64, backFill chan utils.StorageDiff, errChan chan error, done chan bool) error {
+	if endingBlock < startingBlock {
+		return errors.New("backfill: ending block number needs to be greater than starting block number")
+	}
+	backFiller.PassedEndingBlock = endingBlock
+	go func(backFill chan utils.StorageDiff, errChan chan error, done chan bool) {
+		errLen := len(backFiller.BackFillErrs)
+		for i, diff := range backFiller.StorageDiffsToReturn {
+			if i < errLen {
+				err := backFiller.BackFillErrs[i]
+				if err != nil {
+					errChan <- err
+					continue
+				}
+			}
+			backFill <- diff
+		}
+		done <- true
+	}(backFill, errChan, done)
+	return nil
+}

libraries/shared/mocks/batch_client.go

@@ -0,0 +1,64 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package mocks
+
+import (
+	"encoding/json"
+	"errors"
+
+	"github.com/ethereum/go-ethereum/statediff"
+	"github.com/vulcanize/vulcanizedb/pkg/eth/client"
+)
+
+// BackFillerClient is a mock client for use in backfiller tests
+type BackFillerClient struct {
+	MappedStateDiffAt map[uint64][]byte
+}
+
+// SetReturnDiffAt method to set what statediffs the mock client returns
+func (mc *BackFillerClient) SetReturnDiffAt(height uint64, diffPayload statediff.Payload) error {
+	if mc.MappedStateDiffAt == nil {
+		mc.MappedStateDiffAt = make(map[uint64][]byte)
+	}
+	by, err := json.Marshal(diffPayload)
+	if err != nil {
+		return err
+	}
+	mc.MappedStateDiffAt[height] = by
+	return nil
+}
+
+// BatchCall mockClient method to simulate batch call to geth
+func (mc *BackFillerClient) BatchCall(batch []client.BatchElem) error {
+	if mc.MappedStateDiffAt == nil {
+		return errors.New("mockclient needs to be initialized with statediff payloads and errors")
+	}
+	for _, batchElem := range batch {
+		if len(batchElem.Args) != 1 {
+			return errors.New("expected batch elem to contain single argument")
+		}
+		blockHeight, ok := batchElem.Args[0].(uint64)
+		if !ok {
+			return errors.New("expected batch elem argument to be a uint64")
+		}
+		err := json.Unmarshal(mc.MappedStateDiffAt[blockHeight], batchElem.Result)
+		if err != nil {
+			return err
+		}
+	}
+	return nil
+}

libraries/shared/mocks/state_diff_fetcher.go

@@ -0,0 +1,50 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package mocks
+
+import (
+	"errors"
+	"sync/atomic"
+
+	"github.com/ethereum/go-ethereum/statediff"
+)
+
+// StateDiffFetcher mock for tests
+type StateDiffFetcher struct {
+	PayloadsToReturn     map[uint64]statediff.Payload
+	FetchErrs            map[uint64]error
+	CalledAtBlockHeights [][]uint64
+	CalledTimes          int64
+}
+
+// FetchStateDiffsAt mock method
+func (fetcher *StateDiffFetcher) FetchStateDiffsAt(blockHeights []uint64) ([]statediff.Payload, error) {
+	if fetcher.PayloadsToReturn == nil {
+		return nil, errors.New("mock StateDiffFetcher needs to be initialized with payloads to return")
+	}
+	atomic.AddInt64(&fetcher.CalledTimes, 1) // thread-safe increment
+	fetcher.CalledAtBlockHeights = append(fetcher.CalledAtBlockHeights, blockHeights)
+	results := make([]statediff.Payload, 0, len(blockHeights))
+	for _, height := range blockHeights {
+		results = append(results, fetcher.PayloadsToReturn[height])
+		err, ok := fetcher.FetchErrs[height]
+		if ok && err != nil {
+			return nil, err
+		}
+	}
+	return results, nil
+}

libraries/shared/mocks/statediff_streamer.go

@@ -0,0 +1,43 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package mocks
+
+import (
+	"github.com/ethereum/go-ethereum/rpc"
+	"github.com/ethereum/go-ethereum/statediff"
+)
+
+// StateDiffStreamer is the underlying struct for the Streamer interface
+type StateDiffStreamer struct {
+	PassedPayloadChan chan statediff.Payload
+	ReturnSub         *rpc.ClientSubscription
+	ReturnErr         error
+	StreamPayloads    []statediff.Payload
+}
+
+// Stream is the main loop for subscribing to data from the Geth state diff process
+func (sds *StateDiffStreamer) Stream(payloadChan chan statediff.Payload) (*rpc.ClientSubscription, error) {
+	sds.PassedPayloadChan = payloadChan
+
+	go func() {
+		for _, payload := range sds.StreamPayloads {
+			sds.PassedPayloadChan <- payload
+		}
+	}()
+
+	return sds.ReturnSub, sds.ReturnErr
+}

libraries/shared/mocks/storage_fetcher.go

@@ -16,20 +16,23 @@
 
 package mocks
 
-import "github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+import (
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+)
 
-type MockStorageFetcher struct {
+// StorageFetcher is a mock fetcher for use in tests with backfilling
+type StorageFetcher struct {
 	DiffsToReturn []utils.StorageDiff
 	ErrsToReturn  []error
 }
 
-func NewMockStorageFetcher() *MockStorageFetcher {
-	return &MockStorageFetcher{}
+// NewStorageFetcher returns a new StorageFetcher
+func NewStorageFetcher() *StorageFetcher {
+	return &StorageFetcher{}
 }
 
-func (fetcher *MockStorageFetcher) FetchStorageDiffs(out chan<- utils.StorageDiff, errs chan<- error) {
-	defer close(out)
-	defer close(errs)
+// FetchStorageDiffs mock method
+func (fetcher *StorageFetcher) FetchStorageDiffs(out chan<- utils.StorageDiff, errs chan<- error) {
 	for _, err := range fetcher.ErrsToReturn {
 		errs <- err
 	}

libraries/shared/mocks/storage_queue.go

@@ -20,27 +20,41 @@ import (
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 )
 
+// MockStorageQueue for tests
 type MockStorageQueue struct {
 	AddCalled       bool
 	AddError        error
-	AddPassedDiff  utils.StorageDiff
+	AddPassedDiffs  map[int]utils.StorageDiff
 	DeleteErr       error
-	DeletePassedID int
+	DeletePassedIds []int
 	GetAllErr       error
-	DiffsToReturn  []utils.StorageDiff
+	DiffsToReturn   map[int]utils.StorageDiff
+	GetAllCalled    bool
 }
 
+// Add mock method
 func (queue *MockStorageQueue) Add(diff utils.StorageDiff) error {
 	queue.AddCalled = true
-	queue.AddPassedDiff = diff
+	if queue.AddPassedDiffs == nil {
+		queue.AddPassedDiffs = make(map[int]utils.StorageDiff)
+	}
+	queue.AddPassedDiffs[diff.ID] = diff
 	return queue.AddError
 }
 
+// Delete mock method
 func (queue *MockStorageQueue) Delete(id int) error {
-	queue.DeletePassedID = id
+	queue.DeletePassedIds = append(queue.DeletePassedIds, id)
+	delete(queue.DiffsToReturn, id)
 	return queue.DeleteErr
 }
 
+// GetAll mock method
 func (queue *MockStorageQueue) GetAll() ([]utils.StorageDiff, error) {
-	return queue.DiffsToReturn, queue.GetAllErr
+	queue.GetAllCalled = true
+	diffs := make([]utils.StorageDiff, 0)
+	for _, diff := range queue.DiffsToReturn {
+		diffs = append(diffs, diff)
+	}
+	return diffs, queue.GetAllErr
 }

libraries/shared/mocks/storage_transformer.go

@@ -18,26 +18,34 @@ package mocks
 
 import (
 	"github.com/ethereum/go-ethereum/common"
+
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
 )
 
+// MockStorageTransformer for tests
 type MockStorageTransformer struct {
 	KeccakOfAddress common.Hash
 	ExecuteErr      error
-	PassedDiff      utils.StorageDiff
+	PassedDiffs     map[int]utils.StorageDiff
 }
 
+// Execute mock method
 func (transformer *MockStorageTransformer) Execute(diff utils.StorageDiff) error {
-	transformer.PassedDiff = diff
+	if transformer.PassedDiffs == nil {
+		transformer.PassedDiffs = make(map[int]utils.StorageDiff)
+	}
+	transformer.PassedDiffs[diff.ID] = diff
 	return transformer.ExecuteErr
 }
 
+// KeccakContractAddress mock method
 func (transformer *MockStorageTransformer) KeccakContractAddress() common.Hash {
 	return transformer.KeccakOfAddress
 }
 
+// FakeTransformerInitializer mock method
 func (transformer *MockStorageTransformer) FakeTransformerInitializer(db *postgres.DB) transformer.StorageTransformer {
 	return transformer
 }

libraries/shared/repository/address_repository_test.go

@@ -17,14 +17,14 @@
 package repository_test
 
 import (
-	"github.com/vulcanize/vulcanizedb/libraries/shared/repository"
-	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"strings"
 
 	"github.com/jmoiron/sqlx"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 
+	"github.com/vulcanize/vulcanizedb/libraries/shared/repository"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
 	"github.com/vulcanize/vulcanizedb/test_config"

libraries/shared/repository/repository_suite_test.go

@@ -19,10 +19,11 @@ package repository_test
 import (
 	"testing"
 
+	"io/ioutil"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	log "github.com/sirupsen/logrus"
-	"io/ioutil"
 )
 
 func TestFactories(t *testing.T) {

libraries/shared/storage/backfiller.go

@@ -0,0 +1,149 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package storage
+
+import (
+	"fmt"
+	"sync/atomic"
+
+	"github.com/ethereum/go-ethereum/common"
+	"github.com/ethereum/go-ethereum/rlp"
+	"github.com/ethereum/go-ethereum/statediff"
+	"github.com/sirupsen/logrus"
+
+	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+)
+
+const (
+	DefaultMaxBatchSize   uint64 = 100
+	defaultMaxBatchNumber int64  = 10
+)
+
+// BackFiller is the backfilling interface
+type BackFiller interface {
+	BackFill(startingBlock, endingBlock uint64, backFill chan utils.StorageDiff, errChan chan error, done chan bool) error
+}
+
+// backFiller is the backfilling struct
+type backFiller struct {
+	fetcher       fetcher.StateDiffFetcher
+	batchSize     uint64
+	startingBlock uint64
+}
+
+// NewStorageBackFiller returns a BackFiller
+func NewStorageBackFiller(fetcher fetcher.StateDiffFetcher, batchSize uint64) BackFiller {
+	if batchSize == 0 {
+		batchSize = DefaultMaxBatchSize
+	}
+	return &backFiller{
+		fetcher:   fetcher,
+		batchSize: batchSize,
+	}
+}
+
+// BackFill fetches, processes, and returns utils.StorageDiffs over a range of blocks
+// It splits a large range up into smaller chunks, batch fetching and processing those chunks concurrently
+func (bf *backFiller) BackFill(startingBlock, endingBlock uint64, backFill chan utils.StorageDiff, errChan chan error, done chan bool) error {
+	logrus.Infof("going to fill in gap from %d to %d", startingBlock, endingBlock)
+
+	// break the range up into bins of smaller ranges
+	blockRangeBins, err := utils.GetBlockHeightBins(startingBlock, endingBlock, bf.batchSize)
+	if err != nil {
+		return err
+	}
+	// int64 for atomic incrementing and decrementing to track the number of active processing goroutines we have
+	var activeCount int64
+	// channel for processing goroutines to signal when they are done
+	processingDone := make(chan [2]uint64)
+	forwardDone := make(chan bool)
+
+	// for each block range bin spin up a goroutine to batch fetch and process state diffs in that range
+	go func() {
+		for _, blockHeights := range blockRangeBins {
+			// if we have reached our limit of active goroutines
+			// wait for one to finish before starting the next
+			if atomic.AddInt64(&activeCount, 1) > defaultMaxBatchNumber {
+				// this blocks until a process signals it has finished
+				<-forwardDone
+			}
+			go bf.backFillRange(blockHeights, backFill, errChan, processingDone)
+		}
+	}()
+
+	// goroutine that listens on the processingDone chan
+	// keeps track of the number of processing goroutines that have finished
+	// when they have all finished, sends the final signal out
+	go func() {
+		goroutinesFinished := 0
+		for {
+			select {
+			case doneWithHeights := <-processingDone:
+				atomic.AddInt64(&activeCount, -1)
+				select {
+				// if we are waiting for a process to finish, signal that one has
+				case forwardDone <- true:
+				default:
+				}
+				logrus.Infof("finished fetching gap sub-bin from %d to %d", doneWithHeights[0], doneWithHeights[1])
+				goroutinesFinished++
+				if goroutinesFinished >= len(blockRangeBins) {
+					done <- true
+					return
+				}
+			}
+		}
+	}()
+
+	return nil
+}
+
+func (bf *backFiller) backFillRange(blockHeights []uint64, diffChan chan utils.StorageDiff, errChan chan error, doneChan chan [2]uint64) {
+	payloads, fetchErr := bf.fetcher.FetchStateDiffsAt(blockHeights)
+	if fetchErr != nil {
+		errChan <- fetchErr
+	}
+	for _, payload := range payloads {
+		stateDiff := new(statediff.StateDiff)
+		stateDiffDecodeErr := rlp.DecodeBytes(payload.StateDiffRlp, stateDiff)
+		if stateDiffDecodeErr != nil {
+			errChan <- stateDiffDecodeErr
+			continue
+		}
+		accounts := utils.GetAccountsFromDiff(*stateDiff)
+		for _, account := range accounts {
+			logrus.Trace(fmt.Sprintf("iterating through %d Storage values on account with key %s", len(account.Storage), common.BytesToHash(account.Key).Hex()))
+			for _, storage := range account.Storage {
+				diff, formatErr := utils.FromGethStateDiff(account, stateDiff, storage)
+				if formatErr != nil {
+					logrus.Error("failed to format utils.StorageDiff from storage with key: ", common.BytesToHash(storage.Key), "from account with key: ", common.BytesToHash(account.Key))
+					errChan <- formatErr
+					continue
+				}
+				logrus.Trace("adding storage diff to results",
+					"keccak of address: ", diff.HashedAddress.Hex(),
+					"block height: ", diff.BlockHeight,
+					"storage key: ", diff.StorageKey.Hex(),
+					"storage value: ", diff.StorageValue.Hex())
+				diffChan <- diff
+			}
+		}
+	}
+	// when this is done, send out a signal
+	doneChan <- [2]uint64{blockHeights[0], blockHeights[len(blockHeights)-1]}
+}

libraries/shared/storage/backfiller_test.go

@@ -0,0 +1,237 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package storage_test
+
+import (
+	"errors"
+
+	"github.com/ethereum/go-ethereum/statediff"
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/vulcanize/vulcanizedb/libraries/shared/mocks"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/test_data"
+)
+
+var _ = Describe("BackFiller", func() {
+	Describe("BackFill", func() {
+		var (
+			mockFetcher *mocks.StateDiffFetcher
+			backFiller  storage.BackFiller
+		)
+		BeforeEach(func() {
+			mockFetcher = new(mocks.StateDiffFetcher)
+			mockFetcher.PayloadsToReturn = map[uint64]statediff.Payload{
+				test_data.BlockNumber.Uint64():  test_data.MockStatediffPayload,
+				test_data.BlockNumber2.Uint64(): test_data.MockStatediffPayload2,
+			}
+		})
+
+		It("batch calls statediff_stateDiffAt", func() {
+			backFiller = storage.NewStorageBackFiller(mockFetcher, 100)
+			backFill := make(chan utils.StorageDiff)
+			done := make(chan bool)
+			errChan := make(chan error)
+			backFillInitErr := backFiller.BackFill(
+				test_data.BlockNumber.Uint64(),
+				test_data.BlockNumber2.Uint64(),
+				backFill,
+				errChan,
+				done)
+			Expect(backFillInitErr).ToNot(HaveOccurred())
+			var diffs []utils.StorageDiff
+			for {
+				select {
+				case diff := <-backFill:
+					diffs = append(diffs, diff)
+					continue
+				case err := <-errChan:
+					Expect(err).ToNot(HaveOccurred())
+					continue
+				case <-done:
+					break
+				}
+				break
+			}
+			Expect(mockFetcher.CalledTimes).To(Equal(int64(1)))
+			Expect(len(diffs)).To(Equal(4))
+			Expect(containsDiff(diffs, test_data.CreatedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.UpdatedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.DeletedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.UpdatedExpectedStorageDiff2)).To(BeTrue())
+		})
+
+		It("has a configurable batch size", func() {
+			backFiller = storage.NewStorageBackFiller(mockFetcher, 1)
+			backFill := make(chan utils.StorageDiff)
+			done := make(chan bool)
+			errChan := make(chan error)
+			backFillInitErr := backFiller.BackFill(
+				test_data.BlockNumber.Uint64(),
+				test_data.BlockNumber2.Uint64(),
+				backFill,
+				errChan,
+				done)
+			Expect(backFillInitErr).ToNot(HaveOccurred())
+			var diffs []utils.StorageDiff
+			for {
+				select {
+				case diff := <-backFill:
+					diffs = append(diffs, diff)
+					continue
+				case err := <-errChan:
+					Expect(err).ToNot(HaveOccurred())
+					continue
+				case <-done:
+					break
+				}
+				break
+			}
+			Expect(mockFetcher.CalledTimes).To(Equal(int64(2)))
+			Expect(len(diffs)).To(Equal(4))
+			Expect(containsDiff(diffs, test_data.CreatedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.UpdatedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.DeletedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.UpdatedExpectedStorageDiff2)).To(BeTrue())
+		})
+
+		It("handles bin numbers in excess of the goroutine limit (100)", func() {
+			payloadsToReturn := make(map[uint64]statediff.Payload, 1001)
+			for i := test_data.BlockNumber.Uint64(); i <= test_data.BlockNumber.Uint64()+1000; i++ {
+				payloadsToReturn[i] = test_data.MockStatediffPayload
+			}
+			mockFetcher.PayloadsToReturn = payloadsToReturn
+			// batch size of 2 with 1001 block range => 501 bins
+			backFiller = storage.NewStorageBackFiller(mockFetcher, 2)
+			backFill := make(chan utils.StorageDiff)
+			done := make(chan bool)
+			errChan := make(chan error)
+			backFillInitErr := backFiller.BackFill(
+				test_data.BlockNumber.Uint64(),
+				test_data.BlockNumber.Uint64()+1000,
+				backFill,
+				errChan,
+				done)
+			Expect(backFillInitErr).ToNot(HaveOccurred())
+			var diffs []utils.StorageDiff
+			for {
+				select {
+				case diff := <-backFill:
+					diffs = append(diffs, diff)
+					continue
+				case err := <-errChan:
+					Expect(err).ToNot(HaveOccurred())
+					continue
+				case <-done:
+					break
+				}
+				break
+			}
+			Expect(mockFetcher.CalledTimes).To(Equal(int64(501)))
+			Expect(len(diffs)).To(Equal(3003))
+			Expect(containsDiff(diffs, test_data.CreatedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.UpdatedExpectedStorageDiff)).To(BeTrue())
+			Expect(containsDiff(diffs, test_data.DeletedExpectedStorageDiff)).To(BeTrue())
+		})
+
+		It("passes fetcher errors forward", func() {
+			mockFetcher.FetchErrs = map[uint64]error{
+				test_data.BlockNumber.Uint64(): errors.New("mock fetcher error"),
+			}
+			backFiller = storage.NewStorageBackFiller(mockFetcher, 1)
+			backFill := make(chan utils.StorageDiff)
+			done := make(chan bool)
+			errChan := make(chan error)
+			backFillInitErr := backFiller.BackFill(
+				test_data.BlockNumber.Uint64(),
+				test_data.BlockNumber2.Uint64(),
+				backFill,
+				errChan,
+				done)
+			Expect(backFillInitErr).ToNot(HaveOccurred())
+			var numOfErrs int
+			var diffs []utils.StorageDiff
+			for {
+				select {
+				case diff := <-backFill:
+					diffs = append(diffs, diff)
+					continue
+				case err := <-errChan:
+					Expect(err).To(HaveOccurred())
+					Expect(err.Error()).To(Equal("mock fetcher error"))
+					numOfErrs++
+					continue
+				case <-done:
+					break
+				}
+				break
+			}
+			Expect(mockFetcher.CalledTimes).To(Equal(int64(2)))
+			Expect(numOfErrs).To(Equal(1))
+			Expect(len(diffs)).To(Equal(1))
+			Expect(containsDiff(diffs, test_data.UpdatedExpectedStorageDiff2)).To(BeTrue())
+
+			mockFetcher.FetchErrs = map[uint64]error{
+				test_data.BlockNumber.Uint64():  errors.New("mock fetcher error"),
+				test_data.BlockNumber2.Uint64(): errors.New("mock fetcher error"),
+			}
+			mockFetcher.CalledTimes = 0
+			backFiller = storage.NewStorageBackFiller(mockFetcher, 1)
+			backFill = make(chan utils.StorageDiff)
+			done = make(chan bool)
+			errChan = make(chan error)
+			backFillInitErr = backFiller.BackFill(
+				test_data.BlockNumber.Uint64(),
+				test_data.BlockNumber2.Uint64(),
+				backFill,
+				errChan,
+				done)
+			Expect(backFillInitErr).ToNot(HaveOccurred())
+			numOfErrs = 0
+			diffs = []utils.StorageDiff{}
+			for {
+				select {
+				case diff := <-backFill:
+					diffs = append(diffs, diff)
+					continue
+				case err := <-errChan:
+					Expect(err).To(HaveOccurred())
+					Expect(err.Error()).To(Equal("mock fetcher error"))
+					numOfErrs++
+					continue
+				case <-done:
+					break
+				}
+				break
+			}
+			Expect(mockFetcher.CalledTimes).To(Equal(int64(2)))
+			Expect(numOfErrs).To(Equal(2))
+			Expect(len(diffs)).To(Equal(0))
+		})
+	})
+})
+
+func containsDiff(diffs []utils.StorageDiff, diff utils.StorageDiff) bool {
+	for _, d := range diffs {
+		if d == diff {
+			return true
+		}
+	}
+	return false
+}

libraries/shared/storage/storage_suite_test.go

@@ -19,10 +19,11 @@ package storage_test
 import (
 	"testing"
 
+	"io/ioutil"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	log "github.com/sirupsen/logrus"
-	"io/ioutil"
 )
 
 func TestFactories(t *testing.T) {

libraries/shared/storage/utils/bins.go

@@ -0,0 +1,45 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package utils
+
+import "errors"
+
+func GetBlockHeightBins(startingBlock, endingBlock, batchSize uint64) ([][]uint64, error) {
+	if endingBlock < startingBlock {
+		return nil, errors.New("backfill: ending block number needs to be greater than starting block number")
+	}
+	if batchSize == 0 {
+		return nil, errors.New("backfill: batchsize needs to be greater than zero")
+	}
+	length := endingBlock - startingBlock + 1
+	numberOfBins := length / batchSize
+	remainder := length % batchSize
+	if remainder != 0 {
+		numberOfBins++
+	}
+	blockRangeBins := make([][]uint64, numberOfBins)
+	for i := range blockRangeBins {
+		nextBinStart := startingBlock + batchSize
+		blockRange := make([]uint64, 0, nextBinStart-startingBlock+1)
+		for j := startingBlock; j < nextBinStart && j <= endingBlock; j++ {
+			blockRange = append(blockRange, j)
+		}
+		startingBlock = nextBinStart
+		blockRangeBins[i] = blockRange
+	}
+	return blockRangeBins, nil
+}

libraries/shared/storage/utils/bins_test.go

@@ -0,0 +1,66 @@
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+package utils_test
+
+import (
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+)
+
+var _ = Describe("GetBlockHeightBins", func() {
+	It("splits a block range up into bins", func() {
+		var startingBlock uint64 = 1
+		var endingBlock uint64 = 10101
+		var batchSize uint64 = 100
+		blockRangeBins, err := utils.GetBlockHeightBins(startingBlock, endingBlock, batchSize)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(len(blockRangeBins)).To(Equal(102))
+		Expect(blockRangeBins[101]).To(Equal([]uint64{10101}))
+
+		startingBlock = 101
+		endingBlock = 10100
+		batchSize = 100
+		lastBin := make([]uint64, 0)
+		for i := 10001; i <= 10100; i++ {
+			lastBin = append(lastBin, uint64(i))
+		}
+		blockRangeBins, err = utils.GetBlockHeightBins(startingBlock, endingBlock, batchSize)
+		Expect(err).ToNot(HaveOccurred())
+		Expect(len(blockRangeBins)).To(Equal(100))
+		Expect(blockRangeBins[99]).To(Equal(lastBin))
+	})
+
+	It("throws an error if the starting block is higher than the ending block", func() {
+		var startingBlock uint64 = 10102
+		var endingBlock uint64 = 10101
+		var batchSize uint64 = 100
+		_, err := utils.GetBlockHeightBins(startingBlock, endingBlock, batchSize)
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("ending block number needs to be greater than starting block number"))
+	})
+
+	It("throws an error if the batch size is zero", func() {
+		var startingBlock uint64 = 1
+		var endingBlock uint64 = 10101
+		var batchSize uint64 = 0
+		_, err := utils.GetBlockHeightBins(startingBlock, endingBlock, batchSize)
+		Expect(err).To(HaveOccurred())
+		Expect(err.Error()).To(ContainSubstring("batchsize needs to be greater than zero"))
+	})
+})

libraries/shared/storage/utils/diff.go

@@ -17,11 +17,12 @@
 package utils
 
 import (
+	"strconv"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/statediff"
-	"strconv"
 )
 
 const ExpectedRowLength = 5
@@ -71,3 +72,8 @@ func FromGethStateDiff(account statediff.AccountDiff, stateDiff *statediff.State
 func HexToKeccak256Hash(hex string) common.Hash {
 	return crypto.Keccak256Hash(common.FromHex(hex))
 }
+
+func GetAccountsFromDiff(stateDiff statediff.StateDiff) []statediff.AccountDiff {
+	accounts := append(stateDiff.CreatedAccounts, stateDiff.UpdatedAccounts...)
+	return append(accounts, stateDiff.DeletedAccounts...)
+}

libraries/shared/storage/utils/diff_test.go

@@ -17,6 +17,9 @@
 package utils_test
 
 import (
+	"math/big"
+	"math/rand"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/statediff"
@@ -25,8 +28,6 @@ import (
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/test_data"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
-	"math/big"
-	"math/rand"
 )
 
 var _ = Describe("Storage row parsing", func() {

libraries/shared/storage/utils/keys_loader.go

@@ -17,9 +17,10 @@
 package utils
 
 import (
+	"math/big"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
-	"math/big"
 )
 
 const (

libraries/shared/storage/utils/utils_suite_test.go

@@ -17,10 +17,11 @@
 package utils_test
 
 import (
-	"github.com/sirupsen/logrus"
 	"io/ioutil"
 	"testing"
 
+	"github.com/sirupsen/logrus"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )

libraries/shared/streamer/statediff_streamer.go

@@ -1,16 +1,18 @@
-// Copyright 2019 Vulcanize
-//
-// Licensed under the Apache License, Version 2.0 (the "License");
-// you may not use this file except in compliance with the License.
-// You may obtain a copy of the License at
-//
-//      http://www.apache.org/licenses/LICENSE-2.0
-//
-// Unless required by applicable law or agreed to in writing, software
-// distributed under the License is distributed on an "AS IS" BASIS,
-// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
-// See the License for the specific language governing permissions and
-// limitations under the License.
+// VulcanizeDB
+// Copyright © 2019 Vulcanize
+
+// This program is free software: you can redistribute it and/or modify
+// it under the terms of the GNU Affero General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// This program is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU Affero General Public License for more details.
+
+// You should have received a copy of the GNU Affero General Public License
+// along with this program.  If not, see <http://www.gnu.org/licenses/>.
 
 package streamer
 
@@ -18,24 +20,29 @@ import (
 	"github.com/ethereum/go-ethereum/rpc"
 	"github.com/ethereum/go-ethereum/statediff"
 	"github.com/sirupsen/logrus"
+
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 )
 
+// Streamer is the interface for streaming a statediff subscription
 type Streamer interface {
-	Stream(chan statediff.Payload) (*rpc.ClientSubscription, error)
+	Stream(payloadChan chan statediff.Payload) (*rpc.ClientSubscription, error)
 }
 
+// StateDiffStreamer is the underlying struct for the StateDiffStreamer interface
 type StateDiffStreamer struct {
-	client core.RPCClient
+	Client core.RPCClient
 }
 
-func (streamer *StateDiffStreamer) Stream(payloadChan chan statediff.Payload) (*rpc.ClientSubscription, error) {
-	logrus.Info("streaming diffs from geth")
-	return streamer.client.Subscribe("statediff", payloadChan, "stream")
-}
-
-func NewStateDiffStreamer(client core.RPCClient) StateDiffStreamer {
-	return StateDiffStreamer{
-		client: client,
+// NewStateDiffStreamer creates a pointer to a new StateDiffStreamer which satisfies the IStateDiffStreamer interface
+func NewStateDiffStreamer(client core.RPCClient) Streamer {
+	return &StateDiffStreamer{
+		Client: client,
 	}
 }
+
+// Stream is the main loop for subscribing to data from the Geth state diff process
+func (sds *StateDiffStreamer) Stream(payloadChan chan statediff.Payload) (*rpc.ClientSubscription, error) {
+	logrus.Info("streaming diffs from geth")
+	return sds.Client.Subscribe("statediff", payloadChan, "stream")
+}

libraries/shared/test_data/generic.go

@@ -17,13 +17,14 @@
 package test_data
 
 import (
+	"math/rand"
+	"time"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/common/hexutil"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/factories/event"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
-	"math/rand"
-	"time"
 )
 
 var startingBlockNumber = rand.Int63()

libraries/shared/test_data/statediff.go

@@ -15,20 +15,23 @@
 package test_data
 
 import (
-	"errors"
+	"math/big"
+	"math/rand"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/state"
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/rlp"
 	"github.com/ethereum/go-ethereum/statediff"
-	"math/big"
-	"math/rand"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 )
 
 var (
 	BlockNumber             = big.NewInt(rand.Int63())
+	BlockNumber2            = big.NewInt(0).Add(BlockNumber, big.NewInt(1))
 	BlockHash               = "0xfa40fbe2d98d98b3363a778d52f2bcd29d6790b9b3f3cab2b167fd12d3550f73"
+	BlockHash2              = "0xaa40fbe2d98d98b3363a778d52f2bcd29d6790b9b3f3cab2b167fd12d3550f72"
 	CodeHash                = common.Hex2Bytes("0xc5d2460186f7233c927e7db2dcc703c0e500b653ca82273b7bfad8045d85a470")
 	NewNonceValue           = rand.Uint64()
 	NewBalanceValue         = rand.Int63()
@@ -44,14 +47,13 @@ var (
 		Proof: [][]byte{},
 	}}
 	LargeStorageValue       = common.Hex2Bytes("00191b53778c567b14b50ba0000")
-	LargeStorageValueRlp, rlpErr = rlp.EncodeToBytes(LargeStorageValue)
+	LargeStorageValueRlp, _ = rlp.EncodeToBytes(LargeStorageValue)
 	storageWithLargeValue   = []statediff.StorageDiff{{
 		Key:   StorageKey,
 		Value: LargeStorageValueRlp,
 		Path:  StoragePath,
 		Proof: [][]byte{},
 	}}
-	EmptyStorage        = make([]statediff.StorageDiff, 0)
 	StorageWithBadValue = statediff.StorageDiff{
 		Key:   StorageKey,
 		Value: []byte{0, 1, 2},
@@ -83,6 +85,11 @@ var (
 		Value:   valueBytes,
 		Storage: storageWithLargeValue,
 	}}
+	UpdatedAccountDiffs2 = []statediff.AccountDiff{{
+		Key:     AnotherContractLeafKey.Bytes(),
+		Value:   valueBytes,
+		Storage: storageWithSmallValue,
+	}}
 
 	DeletedAccountDiffs = []statediff.AccountDiff{{
 		Key:     AnotherContractLeafKey.Bytes(),
@@ -97,7 +104,15 @@ var (
 		DeletedAccounts: DeletedAccountDiffs,
 		UpdatedAccounts: UpdatedAccountDiffs,
 	}
+	MockStateDiff2 = statediff.StateDiff{
+		BlockNumber:     BlockNumber2,
+		BlockHash:       common.HexToHash(BlockHash2),
+		CreatedAccounts: nil,
+		DeletedAccounts: nil,
+		UpdatedAccounts: UpdatedAccountDiffs2,
+	}
 	MockStateDiffBytes, _  = rlp.EncodeToBytes(MockStateDiff)
+	MockStateDiff2Bytes, _ = rlp.EncodeToBytes(MockStateDiff2)
 
 	mockTransaction1 = types.NewTransaction(0, common.HexToAddress("0x0"), big.NewInt(1000), 50, big.NewInt(100), nil)
 	mockTransaction2 = types.NewTransaction(1, common.HexToAddress("0x1"), big.NewInt(2000), 100, big.NewInt(200), nil)
@@ -114,24 +129,57 @@ var (
 		TxHash:      common.HexToHash("0x0"),
 		ReceiptHash: common.HexToHash("0x0"),
 	}
+	MockHeader2 = types.Header{
+		Time:        0,
+		Number:      BlockNumber2,
+		Root:        common.HexToHash("0x1"),
+		TxHash:      common.HexToHash("0x1"),
+		ReceiptHash: common.HexToHash("0x1"),
+	}
 	MockBlock        = types.NewBlock(&MockHeader, MockTransactions, nil, MockReceipts)
+	MockBlock2       = types.NewBlock(&MockHeader2, MockTransactions, nil, MockReceipts)
 	MockBlockRlp, _  = rlp.EncodeToBytes(MockBlock)
+	MockBlockRlp2, _ = rlp.EncodeToBytes(MockBlock2)
 
 	MockStatediffPayload = statediff.Payload{
 		BlockRlp:     MockBlockRlp,
 		StateDiffRlp: MockStateDiffBytes,
-		Err:          nil,
+	}
+	MockStatediffPayload2 = statediff.Payload{
+		BlockRlp:     MockBlockRlp2,
+		StateDiffRlp: MockStateDiff2Bytes,
 	}
 
-	EmptyStatediffPayload = statediff.Payload{
-		BlockRlp:     []byte{},
-		StateDiffRlp: []byte{},
-		Err:          nil,
+	CreatedExpectedStorageDiff = utils.StorageDiff{
+		ID:            0,
+		HashedAddress: common.BytesToHash(ContractLeafKey[:]),
+		BlockHash:     common.HexToHash(BlockHash),
+		BlockHeight:   int(BlockNumber.Int64()),
+		StorageKey:    common.BytesToHash(StorageKey),
+		StorageValue:  common.BytesToHash(SmallStorageValue),
 	}
-
-	ErrStatediffPayload = statediff.Payload{
-		BlockRlp:     []byte{},
-		StateDiffRlp: []byte{},
-		Err:          errors.New("mock error"),
+	UpdatedExpectedStorageDiff = utils.StorageDiff{
+		ID:            0,
+		HashedAddress: common.BytesToHash(AnotherContractLeafKey[:]),
+		BlockHash:     common.HexToHash(BlockHash),
+		BlockHeight:   int(BlockNumber.Int64()),
+		StorageKey:    common.BytesToHash(StorageKey),
+		StorageValue:  common.BytesToHash(LargeStorageValue),
+	}
+	UpdatedExpectedStorageDiff2 = utils.StorageDiff{
+		ID:            0,
+		HashedAddress: common.BytesToHash(AnotherContractLeafKey[:]),
+		BlockHash:     common.HexToHash(BlockHash2),
+		BlockHeight:   int(BlockNumber2.Int64()),
+		StorageKey:    common.BytesToHash(StorageKey),
+		StorageValue:  common.BytesToHash(SmallStorageValue),
+	}
+	DeletedExpectedStorageDiff = utils.StorageDiff{
+		ID:            0,
+		HashedAddress: common.BytesToHash(AnotherContractLeafKey[:]),
+		BlockHash:     common.HexToHash(BlockHash),
+		BlockHeight:   int(BlockNumber.Int64()),
+		StorageKey:    common.BytesToHash(StorageKey),
+		StorageValue:  common.BytesToHash(SmallStorageValue),
 	}
 )

libraries/shared/test_data/test_helpers.go

@@ -1,13 +1,14 @@
 package test_data
 
 import (
+	"math/rand"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/core/types"
 	. "github.com/onsi/gomega"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres/repositories"
-	"math/rand"
 )
 
 // Create a header sync log to reference in an event, returning inserted header sync log

libraries/shared/watcher/event_watcher.go

@@ -17,7 +17,10 @@
 package watcher
 
 import (
+	"time"
+
 	"github.com/sirupsen/logrus"
+
 	"github.com/vulcanize/vulcanizedb/libraries/shared/chunker"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/constants"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
@@ -27,7 +30,6 @@ import (
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres/repositories"
-	"time"
 )
 
 const NoNewDataPause = time.Second * 7

libraries/shared/watcher/event_watcher_test.go

@@ -18,6 +18,7 @@ package watcher_test
 
 import (
 	"errors"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/constants"

libraries/shared/watcher/storage_watcher.go

@@ -18,19 +18,22 @@ package watcher
 
 import (
 	"fmt"
+	"time"
+
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/sirupsen/logrus"
+
 	"github.com/vulcanize/vulcanizedb/libraries/shared/fetcher"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
-	"time"
 )
 
 type IStorageWatcher interface {
 	AddTransformers(initializers []transformer.StorageTransformerInitializer)
-	Execute(diffsChan chan utils.StorageDiff, errsChan chan error, queueRecheckInterval time.Duration)
+	Execute(queueRecheckInterval time.Duration, backFillOn bool)
+	BackFill(startingBlock uint64, backFiller storage.BackFiller)
 }
 
 type StorageWatcher struct {
@@ -38,42 +41,69 @@ type StorageWatcher struct {
 	StorageFetcher            fetcher.IStorageFetcher
 	Queue                     storage.IStorageQueue
 	KeccakAddressTransformers map[common.Hash]transformer.StorageTransformer // keccak hash of an address => transformer
+	DiffsChan                 chan utils.StorageDiff
+	ErrsChan                  chan error
+	BackFillDoneChan          chan bool
+	StartingSyncBlockChan     chan uint64
 }
 
-func NewStorageWatcher(fetcher fetcher.IStorageFetcher, db *postgres.DB) StorageWatcher {
+func NewStorageWatcher(f fetcher.IStorageFetcher, db *postgres.DB) *StorageWatcher {
 	queue := storage.NewStorageQueue(db)
 	transformers := make(map[common.Hash]transformer.StorageTransformer)
-	return StorageWatcher{
+	return &StorageWatcher{
 		db:                        db,
-		StorageFetcher:            fetcher,
+		StorageFetcher:            f,
+		DiffsChan:                 make(chan utils.StorageDiff, fetcher.PayloadChanBufferSize),
+		ErrsChan:                  make(chan error),
+		StartingSyncBlockChan:     make(chan uint64),
+		BackFillDoneChan:          make(chan bool),
 		Queue:                     queue,
 		KeccakAddressTransformers: transformers,
 	}
 }
 
-func (storageWatcher StorageWatcher) AddTransformers(initializers []transformer.StorageTransformerInitializer) {
+func (storageWatcher *StorageWatcher) AddTransformers(initializers []transformer.StorageTransformerInitializer) {
 	for _, initializer := range initializers {
 		storageTransformer := initializer(storageWatcher.db)
 		storageWatcher.KeccakAddressTransformers[storageTransformer.KeccakContractAddress()] = storageTransformer
 	}
 }
 
-func (storageWatcher StorageWatcher) Execute(diffsChan chan utils.StorageDiff, errsChan chan error, queueRecheckInterval time.Duration) {
+// BackFill uses a backFiller to backfill missing storage diffs for the storageWatcher
+func (storageWatcher *StorageWatcher) BackFill(startingBlock uint64, backFiller storage.BackFiller) {
+	// this blocks until the Execute process sends us the first block number it sees
+	endBackFillBlock := <-storageWatcher.StartingSyncBlockChan
+	backFillInitErr := backFiller.BackFill(startingBlock, endBackFillBlock,
+		storageWatcher.DiffsChan, storageWatcher.ErrsChan, storageWatcher.BackFillDoneChan)
+	if backFillInitErr != nil {
+		logrus.Warn(backFillInitErr)
+	}
+}
+
+// Execute runs the StorageWatcher processes
+func (storageWatcher *StorageWatcher) Execute(queueRecheckInterval time.Duration, backFillOn bool) {
 	ticker := time.NewTicker(queueRecheckInterval)
-	go storageWatcher.StorageFetcher.FetchStorageDiffs(diffsChan, errsChan)
+	go storageWatcher.StorageFetcher.FetchStorageDiffs(storageWatcher.DiffsChan, storageWatcher.ErrsChan)
+	start := true
 	for {
 		select {
-		case fetchErr := <-errsChan:
-			logrus.Warn(fmt.Sprintf("error fetching storage diffs: %s", fetchErr))
-		case diff := <-diffsChan:
+		case fetchErr := <-storageWatcher.ErrsChan:
+			logrus.Warn(fmt.Sprintf("error fetching storage diffs: %s", fetchErr.Error()))
+		case diff := <-storageWatcher.DiffsChan:
+			if start && backFillOn {
+				storageWatcher.StartingSyncBlockChan <- uint64(diff.BlockHeight - 1)
+				start = false
+			}
 			storageWatcher.processRow(diff)
 		case <-ticker.C:
 			storageWatcher.processQueue()
+		case <-storageWatcher.BackFillDoneChan:
+			logrus.Info("storage watcher backfill process has finished")
 		}
 	}
 }
 
-func (storageWatcher StorageWatcher) getTransformer(diff utils.StorageDiff) (transformer.StorageTransformer, bool) {
+func (storageWatcher *StorageWatcher) getTransformer(diff utils.StorageDiff) (transformer.StorageTransformer, bool) {
 	storageTransformer, ok := storageWatcher.KeccakAddressTransformers[diff.HashedAddress]
 	return storageTransformer, ok
 }

libraries/shared/watcher/storage_watcher_test.go

@@ -17,19 +17,24 @@
 package watcher_test
 
 import (
+	"errors"
+	"io/ioutil"
+	"os"
+	"sort"
+	"time"
+
 	"github.com/ethereum/go-ethereum/common"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 	"github.com/sirupsen/logrus"
+
 	"github.com/vulcanize/vulcanizedb/libraries/shared/mocks"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/storage/utils"
+	"github.com/vulcanize/vulcanizedb/libraries/shared/test_data"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/transformer"
 	"github.com/vulcanize/vulcanizedb/libraries/shared/watcher"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
 	"github.com/vulcanize/vulcanizedb/test_config"
-	"io/ioutil"
-	"os"
-	"time"
 )
 
 var _ = Describe("Storage Watcher", func() {
@@ -37,31 +42,26 @@ var _ = Describe("Storage Watcher", func() {
 		It("adds transformers", func() {
 			fakeHashedAddress := utils.HexToKeccak256Hash("0x12345")
 			fakeTransformer := &mocks.MockStorageTransformer{KeccakOfAddress: fakeHashedAddress}
-			w := watcher.NewStorageWatcher(mocks.NewMockStorageFetcher(), test_config.NewTestDB(test_config.NewTestNode()))
+			w := watcher.NewStorageWatcher(mocks.NewStorageFetcher(), test_config.NewTestDB(test_config.NewTestNode()))
 
 			w.AddTransformers([]transformer.StorageTransformerInitializer{fakeTransformer.FakeTransformerInitializer})
 
 			Expect(w.KeccakAddressTransformers[fakeHashedAddress]).To(Equal(fakeTransformer))
 		})
 	})
-
 	Describe("Execute", func() {
 		var (
-			errs            chan error
-			mockFetcher     *mocks.MockStorageFetcher
+			mockFetcher     *mocks.StorageFetcher
 			mockQueue       *mocks.MockStorageQueue
 			mockTransformer *mocks.MockStorageTransformer
 			csvDiff         utils.StorageDiff
-			diffs           chan utils.StorageDiff
-			storageWatcher  watcher.StorageWatcher
+			storageWatcher  *watcher.StorageWatcher
 			hashedAddress   common.Hash
 		)
 
 		BeforeEach(func() {
-			errs = make(chan error)
-			diffs = make(chan utils.StorageDiff)
 			hashedAddress = utils.HexToKeccak256Hash("0x0123456789abcdef")
-			mockFetcher = mocks.NewMockStorageFetcher()
+			mockFetcher = mocks.NewStorageFetcher()
 			mockQueue = &mocks.MockStorageQueue{}
 			mockTransformer = &mocks.MockStorageTransformer{KeccakOfAddress: hashedAddress}
 			csvDiff = utils.StorageDiff{
@@ -84,7 +84,7 @@ var _ = Describe("Storage Watcher", func() {
 			defer os.Remove(tempFile.Name())
 			logrus.SetOutput(tempFile)
 
-			go storageWatcher.Execute(diffs, errs, time.Hour)
+			go storageWatcher.Execute(time.Hour, false)
 
 			Eventually(func() (string, error) {
 				logContent, err := ioutil.ReadFile(tempFile.Name())
@@ -102,25 +102,29 @@ var _ = Describe("Storage Watcher", func() {
 			})
 
 			It("executes transformer for recognized storage diff", func(done Done) {
-				go storageWatcher.Execute(diffs, errs, time.Hour)
+				go storageWatcher.Execute(time.Hour, false)
 
-				Eventually(func() utils.StorageDiff {
-					return mockTransformer.PassedDiff
-				}).Should(Equal(csvDiff))
+				Eventually(func() map[int]utils.StorageDiff {
+					return mockTransformer.PassedDiffs
+				}).Should(Equal(map[int]utils.StorageDiff{
+					csvDiff.ID: csvDiff,
+				}))
 				close(done)
 			})
 
 			It("queues diff for later processing if transformer execution fails", func(done Done) {
 				mockTransformer.ExecuteErr = fakes.FakeError
 
-				go storageWatcher.Execute(diffs, errs, time.Hour)
+				go storageWatcher.Execute(time.Hour, false)
 
-				Expect(<-errs).To(BeNil())
 				Eventually(func() bool {
 					return mockQueue.AddCalled
 				}).Should(BeTrue())
 				Eventually(func() utils.StorageDiff {
-					return mockQueue.AddPassedDiff
+					if len(mockQueue.AddPassedDiffs) > 0 {
+						return mockQueue.AddPassedDiffs[csvDiff.ID]
+					}
+					return utils.StorageDiff{}
 				}).Should(Equal(csvDiff))
 				close(done)
 			})
@@ -133,7 +137,7 @@ var _ = Describe("Storage Watcher", func() {
 				defer os.Remove(tempFile.Name())
 				logrus.SetOutput(tempFile)
 
-				go storageWatcher.Execute(diffs, errs, time.Hour)
+				go storageWatcher.Execute(time.Hour, false)
 
 				Eventually(func() bool {
 					return mockQueue.AddCalled
@@ -148,26 +152,34 @@ var _ = Describe("Storage Watcher", func() {
 
 		Describe("transforming queued storage diffs", func() {
 			BeforeEach(func() {
-				mockQueue.DiffsToReturn = []utils.StorageDiff{csvDiff}
+				mockQueue.DiffsToReturn = map[int]utils.StorageDiff{
+					csvDiff.ID: csvDiff,
+				}
 				storageWatcher = watcher.NewStorageWatcher(mockFetcher, test_config.NewTestDB(test_config.NewTestNode()))
 				storageWatcher.Queue = mockQueue
 				storageWatcher.AddTransformers([]transformer.StorageTransformerInitializer{mockTransformer.FakeTransformerInitializer})
 			})
 
 			It("executes transformer for storage diff", func(done Done) {
-				go storageWatcher.Execute(diffs, errs, time.Nanosecond)
+				go storageWatcher.Execute(time.Nanosecond, false)
 
 				Eventually(func() utils.StorageDiff {
-					return mockTransformer.PassedDiff
+					if len(mockTransformer.PassedDiffs) > 0 {
+						return mockTransformer.PassedDiffs[csvDiff.ID]
+					}
+					return utils.StorageDiff{}
 				}).Should(Equal(csvDiff))
 				close(done)
 			})
 
 			It("deletes diff from queue if transformer execution successful", func(done Done) {
-				go storageWatcher.Execute(diffs, errs, time.Nanosecond)
+				go storageWatcher.Execute(time.Nanosecond, false)
 
 				Eventually(func() int {
-					return mockQueue.DeletePassedID
+					if len(mockQueue.DeletePassedIds) > 0 {
+						return mockQueue.DeletePassedIds[0]
+					}
+					return 0
 				}).Should(Equal(csvDiff.ID))
 				close(done)
 			})
@@ -179,7 +191,7 @@ var _ = Describe("Storage Watcher", func() {
 				defer os.Remove(tempFile.Name())
 				logrus.SetOutput(tempFile)
 
-				go storageWatcher.Execute(diffs, errs, time.Nanosecond)
+				go storageWatcher.Execute(time.Nanosecond, false)
 
 				Eventually(func() (string, error) {
 					logContent, err := ioutil.ReadFile(tempFile.Name())
@@ -193,12 +205,17 @@ var _ = Describe("Storage Watcher", func() {
 					ID:            csvDiff.ID + 1,
 					HashedAddress: utils.HexToKeccak256Hash("0xfedcba9876543210"),
 				}
-				mockQueue.DiffsToReturn = []utils.StorageDiff{obsoleteDiff}
+				mockQueue.DiffsToReturn = map[int]utils.StorageDiff{
+					obsoleteDiff.ID: obsoleteDiff,
+				}
 
-				go storageWatcher.Execute(diffs, errs, time.Nanosecond)
+				go storageWatcher.Execute(time.Nanosecond, false)
 
 				Eventually(func() int {
-					return mockQueue.DeletePassedID
+					if len(mockQueue.DeletePassedIds) > 0 {
+						return mockQueue.DeletePassedIds[0]
+					}
+					return 0
 				}).Should(Equal(obsoleteDiff.ID))
 				close(done)
 			})
@@ -208,14 +225,16 @@ var _ = Describe("Storage Watcher", func() {
 					ID:            csvDiff.ID + 1,
 					HashedAddress: utils.HexToKeccak256Hash("0xfedcba9876543210"),
 				}
-				mockQueue.DiffsToReturn = []utils.StorageDiff{obsoleteDiff}
+				mockQueue.DiffsToReturn = map[int]utils.StorageDiff{
+					obsoleteDiff.ID: obsoleteDiff,
+				}
 				mockQueue.DeleteErr = fakes.FakeError
 				tempFile, fileErr := ioutil.TempFile("", "log")
 				Expect(fileErr).NotTo(HaveOccurred())
 				defer os.Remove(tempFile.Name())
 				logrus.SetOutput(tempFile)
 
-				go storageWatcher.Execute(diffs, errs, time.Nanosecond)
+				go storageWatcher.Execute(time.Nanosecond, false)
 
 				Eventually(func() (string, error) {
 					logContent, err := ioutil.ReadFile(tempFile.Name())
@@ -225,4 +244,236 @@ var _ = Describe("Storage Watcher", func() {
 			})
 		})
 	})
+
+	Describe("BackFill", func() {
+		var (
+			mockFetcher                                          *mocks.StorageFetcher
+			mockBackFiller                                       *mocks.BackFiller
+			mockQueue                                            *mocks.MockStorageQueue
+			mockTransformer                                      *mocks.MockStorageTransformer
+			mockTransformer2                                     *mocks.MockStorageTransformer
+			mockTransformer3                                     *mocks.MockStorageTransformer
+			csvDiff                                              utils.StorageDiff
+			storageWatcher                                       *watcher.StorageWatcher
+			hashedAddress                                        common.Hash
+			createdDiff, updatedDiff1, deletedDiff, updatedDiff2 utils.StorageDiff
+		)
+
+		BeforeEach(func() {
+			createdDiff = test_data.CreatedExpectedStorageDiff
+			createdDiff.ID = 1333
+			updatedDiff1 = test_data.UpdatedExpectedStorageDiff
+			updatedDiff1.ID = 1334
+			deletedDiff = test_data.DeletedExpectedStorageDiff
+			deletedDiff.ID = 1335
+			updatedDiff2 = test_data.UpdatedExpectedStorageDiff2
+			updatedDiff2.ID = 1336
+			mockBackFiller = new(mocks.BackFiller)
+			hashedAddress = utils.HexToKeccak256Hash("0x0123456789abcdef")
+			mockFetcher = mocks.NewStorageFetcher()
+			mockQueue = &mocks.MockStorageQueue{}
+			mockTransformer = &mocks.MockStorageTransformer{KeccakOfAddress: hashedAddress}
+			mockTransformer2 = &mocks.MockStorageTransformer{KeccakOfAddress: common.BytesToHash(test_data.ContractLeafKey[:])}
+			mockTransformer3 = &mocks.MockStorageTransformer{KeccakOfAddress: common.BytesToHash(test_data.AnotherContractLeafKey[:])}
+			csvDiff = utils.StorageDiff{
+				ID:            1337,
+				HashedAddress: hashedAddress,
+				BlockHash:     common.HexToHash("0xfedcba9876543210"),
+				BlockHeight:   int(test_data.BlockNumber2.Int64()) + 1,
+				StorageKey:    common.HexToHash("0xabcdef1234567890"),
+				StorageValue:  common.HexToHash("0x9876543210abcdef"),
+			}
+		})
+
+		Describe("transforming streamed and backfilled storage diffs", func() {
+			BeforeEach(func() {
+				mockFetcher.DiffsToReturn = []utils.StorageDiff{csvDiff}
+				mockBackFiller.SetStorageDiffsToReturn([]utils.StorageDiff{
+					createdDiff,
+					updatedDiff1,
+					deletedDiff,
+					updatedDiff2,
+				})
+				mockQueue.DiffsToReturn = map[int]utils.StorageDiff{}
+				storageWatcher = watcher.NewStorageWatcher(mockFetcher, test_config.NewTestDB(test_config.NewTestNode()))
+				storageWatcher.Queue = mockQueue
+				storageWatcher.AddTransformers([]transformer.StorageTransformerInitializer{
+					mockTransformer.FakeTransformerInitializer,
+					mockTransformer2.FakeTransformerInitializer,
+					mockTransformer3.FakeTransformerInitializer,
+				})
+			})
+
+			It("executes transformer for storage diffs received from fetcher and backfiller", func(done Done) {
+				go storageWatcher.BackFill(test_data.BlockNumber.Uint64(), mockBackFiller)
+				go storageWatcher.Execute(time.Hour, true)
+
+				Eventually(func() int {
+					return len(mockTransformer.PassedDiffs)
+				}).Should(Equal(1))
+
+				Eventually(func() int {
+					return len(mockTransformer2.PassedDiffs)
+				}).Should(Equal(1))
+
+				Eventually(func() int {
+					return len(mockTransformer3.PassedDiffs)
+				}).Should(Equal(3))
+				Expect(mockBackFiller.PassedEndingBlock).To(Equal(uint64(test_data.BlockNumber2.Int64())))
+				Expect(mockTransformer.PassedDiffs[csvDiff.ID]).To(Equal(csvDiff))
+				Expect(mockTransformer2.PassedDiffs[createdDiff.ID]).To(Equal(createdDiff))
+				Expect(mockTransformer3.PassedDiffs[updatedDiff1.ID]).To(Equal(updatedDiff1))
+				Expect(mockTransformer3.PassedDiffs[deletedDiff.ID]).To(Equal(deletedDiff))
+				Expect(mockTransformer3.PassedDiffs[updatedDiff2.ID]).To(Equal(updatedDiff2))
+				close(done)
+			})
+
+			It("adds diffs to the queue if transformation fails", func(done Done) {
+				mockTransformer3.ExecuteErr = fakes.FakeError
+				go storageWatcher.BackFill(test_data.BlockNumber.Uint64(), mockBackFiller)
+				go storageWatcher.Execute(time.Hour, true)
+
+				Eventually(func() int {
+					return len(mockTransformer.PassedDiffs)
+				}).Should(Equal(1))
+				Eventually(func() int {
+					return len(mockTransformer2.PassedDiffs)
+				}).Should(Equal(1))
+				Eventually(func() int {
+					return len(mockTransformer3.PassedDiffs)
+				}).Should(Equal(3))
+
+				Eventually(func() bool {
+					return mockQueue.AddCalled
+				}).Should(BeTrue())
+				Eventually(func() map[int]utils.StorageDiff {
+					if len(mockQueue.AddPassedDiffs) > 2 {
+						return mockQueue.AddPassedDiffs
+					}
+					return map[int]utils.StorageDiff{}
+				}).Should(Equal(map[int]utils.StorageDiff{
+					updatedDiff1.ID: updatedDiff1,
+					deletedDiff.ID:  deletedDiff,
+					updatedDiff2.ID: updatedDiff2,
+				}))
+
+				Expect(mockBackFiller.PassedEndingBlock).To(Equal(uint64(test_data.BlockNumber2.Int64())))
+				Expect(mockTransformer.PassedDiffs[csvDiff.ID]).To(Equal(csvDiff))
+				Expect(mockTransformer2.PassedDiffs[createdDiff.ID]).To(Equal(createdDiff))
+				Expect(mockTransformer3.PassedDiffs[updatedDiff1.ID]).To(Equal(updatedDiff1))
+				Expect(mockTransformer3.PassedDiffs[deletedDiff.ID]).To(Equal(deletedDiff))
+				Expect(mockTransformer3.PassedDiffs[updatedDiff2.ID]).To(Equal(updatedDiff2))
+				close(done)
+			})
+
+			It("logs a backfill error", func(done Done) {
+				tempFile, fileErr := ioutil.TempFile("", "log")
+				Expect(fileErr).NotTo(HaveOccurred())
+				defer os.Remove(tempFile.Name())
+				logrus.SetOutput(tempFile)
+
+				mockBackFiller.BackFillErrs = []error{
+					nil,
+					nil,
+					nil,
+					errors.New("mock backfiller error"),
+				}
+
+				go storageWatcher.BackFill(test_data.BlockNumber.Uint64(), mockBackFiller)
+				go storageWatcher.Execute(time.Hour, true)
+
+				Eventually(func() int {
+					return len(mockTransformer.PassedDiffs)
+				}).Should(Equal(1))
+				Eventually(func() int {
+					return len(mockTransformer2.PassedDiffs)
+				}).Should(Equal(1))
+				Eventually(func() int {
+					return len(mockTransformer3.PassedDiffs)
+				}).Should(Equal(2))
+				Eventually(func() (string, error) {
+					logContent, err := ioutil.ReadFile(tempFile.Name())
+					return string(logContent), err
+				}).Should(ContainSubstring("mock backfiller error"))
+				close(done)
+			})
+
+			It("logs when backfill finishes", func(done Done) {
+				tempFile, fileErr := ioutil.TempFile("", "log")
+				Expect(fileErr).NotTo(HaveOccurred())
+				defer os.Remove(tempFile.Name())
+				logrus.SetOutput(tempFile)
+
+				go storageWatcher.BackFill(test_data.BlockNumber.Uint64(), mockBackFiller)
+				go storageWatcher.Execute(time.Hour, true)
+
+				Eventually(func() (string, error) {
+					logContent, err := ioutil.ReadFile(tempFile.Name())
+					return string(logContent), err
+				}).Should(ContainSubstring("storage watcher backfill process has finished"))
+				close(done)
+			})
+		})
+
+		Describe("transforms queued storage diffs", func() {
+			BeforeEach(func() {
+				mockQueue.DiffsToReturn = map[int]utils.StorageDiff{
+					csvDiff.ID:      csvDiff,
+					createdDiff.ID:  createdDiff,
+					updatedDiff1.ID: updatedDiff1,
+					deletedDiff.ID:  deletedDiff,
+					updatedDiff2.ID: updatedDiff2,
+				}
+				storageWatcher = watcher.NewStorageWatcher(mockFetcher, test_config.NewTestDB(test_config.NewTestNode()))
+				storageWatcher.Queue = mockQueue
+				storageWatcher.AddTransformers([]transformer.StorageTransformerInitializer{
+					mockTransformer.FakeTransformerInitializer,
+					mockTransformer2.FakeTransformerInitializer,
+					mockTransformer3.FakeTransformerInitializer,
+				})
+			})
+
+			It("executes transformers on queued storage diffs", func(done Done) {
+				go storageWatcher.BackFill(test_data.BlockNumber.Uint64(), mockBackFiller)
+				go storageWatcher.Execute(time.Nanosecond, true)
+
+				Eventually(func() int {
+					return len(mockTransformer.PassedDiffs)
+				}).Should(Equal(1))
+				Eventually(func() int {
+					return len(mockTransformer2.PassedDiffs)
+				}).Should(Equal(1))
+				Eventually(func() int {
+					return len(mockTransformer3.PassedDiffs)
+				}).Should(Equal(3))
+				Eventually(func() bool {
+					return mockQueue.GetAllCalled
+				}).Should(BeTrue())
+				sortedExpectedIDs := []int{
+					csvDiff.ID,
+					createdDiff.ID,
+					updatedDiff1.ID,
+					deletedDiff.ID,
+					updatedDiff2.ID,
+				}
+				sort.Ints(sortedExpectedIDs)
+				Eventually(func() []int {
+					if len(mockQueue.DeletePassedIds) > 4 {
+						sort.Ints(mockQueue.DeletePassedIds)
+						return mockQueue.DeletePassedIds
+					}
+					return []int{}
+				}).Should(Equal(sortedExpectedIDs))
+
+				Expect(mockQueue.AddCalled).To(Not(BeTrue()))
+				Expect(len(mockQueue.DiffsToReturn)).To(Equal(0))
+				Expect(mockTransformer.PassedDiffs[csvDiff.ID]).To(Equal(csvDiff))
+				Expect(mockTransformer2.PassedDiffs[createdDiff.ID]).To(Equal(createdDiff))
+				Expect(mockTransformer3.PassedDiffs[updatedDiff1.ID]).To(Equal(updatedDiff1))
+				Expect(mockTransformer3.PassedDiffs[deletedDiff.ID]).To(Equal(deletedDiff))
+				Expect(mockTransformer3.PassedDiffs[updatedDiff2.ID]).To(Equal(updatedDiff2))
+				close(done)
+			})
+		})
+	})
 })

libraries/shared/watcher/watcher_suite_test.go

@@ -17,10 +17,11 @@
 package watcher_test
 
 import (
-	log "github.com/sirupsen/logrus"
 	"io/ioutil"
 	"testing"
 
+	log "github.com/sirupsen/logrus"
+
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
 )

pkg/contract_watcher/header/transformer/transformer.go

@@ -20,6 +20,7 @@ import (
 	"database/sql"
 	"errors"
 	"fmt"
+	"math"
 	"strings"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -105,7 +106,7 @@ func (tr *Transformer) Init() error {
 	tr.sortedMethodIds = make(map[string][]string) // Map to sort method column ids by contract, for post fetch method polling
 	tr.eventIds = make([]string, 0)                // Holds event column ids across all contract, for batch fetching of headers
 	tr.eventFilters = make([]common.Hash, 0)       // Holds topic0 hashes across all contracts, for batch fetching of logs
-	tr.Start = 100000000000
+	tr.Start = math.MaxInt64
 
 	// Iterate through all internal contract addresses
 	for contractAddr := range tr.Config.Addresses {

pkg/eth/eth_suite_test.go

@@ -25,5 +25,5 @@ import (
 
 func TestGeth(t *testing.T) {
 	RegisterFailHandler(Fail)
-	RunSpecs(t, "eth Suite")
+	RunSpecs(t, "Eth Suite")
 }

pkg/eth/node/node.go

@@ -18,17 +18,15 @@ package node
 
 import (
 	"context"
-
-	"strconv"
-
 	"regexp"
-
-	"log"
+	"strconv"
+	"strings"
 
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/p2p"
+	log "github.com/sirupsen/logrus"
+
 	"github.com/vulcanize/vulcanizedb/pkg/core"
-	"strings"
 )
 
 type IPropertiesReader interface {
@@ -101,7 +99,7 @@ func (reader PropertiesReader) NetworkID() float64 {
 	var version string
 	err := reader.client.CallContext(context.Background(), &version, "net_version")
 	if err != nil {
-		log.Println(err)
+		log.Error(err)
 	}
 	networkID, _ := strconv.ParseFloat(version, 64)
 	return networkID
@@ -111,13 +109,19 @@ func (reader PropertiesReader) GenesisBlock() string {
 	var header *types.Header
 	blockZero := "0x0"
 	includeTransactions := false
-	reader.client.CallContext(context.Background(), &header, "eth_getBlockByNumber", blockZero, includeTransactions)
+	err := reader.client.CallContext(context.Background(), &header, "eth_getBlockByNumber", blockZero, includeTransactions)
+	if err != nil {
+		log.Error(err)
+	}
 	return header.Hash().Hex()
 }
 
 func (reader PropertiesReader) NodeInfo() (string, string) {
 	var info p2p.NodeInfo
-	reader.client.CallContext(context.Background(), &info, "admin_nodeInfo")
+	err := reader.client.CallContext(context.Background(), &info, "admin_nodeInfo")
+	if err != nil {
+		log.Error(err)
+	}
 	return info.ID, info.Name
 }
 
@@ -137,14 +141,20 @@ func (client GanacheClient) NodeInfo() (string, string) {
 
 func (client ParityClient) parityNodeInfo() string {
 	var nodeInfo core.ParityNodeInfo
-	client.client.CallContext(context.Background(), &nodeInfo, "parity_versionInfo")
+	err := client.client.CallContext(context.Background(), &nodeInfo, "parity_versionInfo")
+	if err != nil {
+		log.Error(err)
+	}
 	return nodeInfo.String()
 }
 
 func (client ParityClient) parityID() string {
 	var enodeID = regexp.MustCompile(`^enode://(.+)@.+$`)
 	var enodeURL string
-	client.client.CallContext(context.Background(), &enodeURL, "parity_enode")
+	err := client.client.CallContext(context.Background(), &enodeURL, "parity_enode")
+	if err != nil {
+		log.Error(err)
+	}
 	enode := enodeID.FindStringSubmatch(enodeURL)
 	if len(enode) < 2 {
 		return ""