Canonical blocks (#108)

* Update Block w/ newest Block

* Add cascading delete to blocks and transactions tables

* Add handling for new conflicting blocks

* Command line version of sliding window n behind HEAD

cmd/populate_blocks/main.go

@@ -17,6 +17,6 @@ func main() {
 	config := cmd.LoadConfig(*environment)
 	blockchain := geth.NewGethBlockchain(config.Client.IPCPath)
 	repository := cmd.LoadPostgres(config.Database, blockchain.Node())
-	numberOfBlocksCreated := history.PopulateBlocks(blockchain, repository, int64(*startingBlockNumber))
+	numberOfBlocksCreated := history.PopulateMissingBlocks(blockchain, repository, int64(*startingBlockNumber))
 	fmt.Printf("Populated %d blocks", numberOfBlocksCreated)
 }

cmd/update_canonical/main.go

@@ -0,0 +1,47 @@
+package main
+
+import (
+	"flag"
+
+	"time"
+
+	"os"
+	"text/template"
+
+	"github.com/8thlight/vulcanizedb/cmd"
+	"github.com/8thlight/vulcanizedb/pkg/blockchain_listener"
+	"github.com/8thlight/vulcanizedb/pkg/core"
+	"github.com/8thlight/vulcanizedb/pkg/geth"
+	"github.com/8thlight/vulcanizedb/pkg/history"
+	"github.com/8thlight/vulcanizedb/pkg/observers"
+)
+
+const windowTemplate = `Validating Existing Blocks
+|{{.LowerBound}}|-- Validation Window --|{{.UpperBound}}| {{.MaxBlockNumber}}(HEAD)
+
+`
+
+func main() {
+	environment := flag.String("environment", "", "Environment name")
+	flag.Parse()
+	config := cmd.LoadConfig(*environment)
+	blockchain := geth.NewGethBlockchain(config.Client.IPCPath)
+	repository := cmd.LoadPostgres(config.Database, blockchain.Node())
+	listener := blockchain_listener.NewBlockchainListener(
+		blockchain,
+		[]core.BlockchainObserver{
+			observers.BlockchainLoggingObserver{},
+			observers.NewBlockchainDbObserver(repository),
+		},
+	)
+	go listener.Start()
+
+	windowSize := 10
+	ticker := time.NewTicker(10 * time.Second)
+	t := template.Must(template.New("window").Parse(windowTemplate))
+	for _ = range ticker.C {
+		window := history.UpdateBlocksWindow(blockchain, repository, windowSize)
+		t.Execute(os.Stdout, window)
+	}
+	ticker.Stop()
+}

db/migrations/1513192766_add_cascade_delete_to_transactions.down.sql

@@ -0,0 +1,11 @@
+BEGIN;
+
+ALTER TABLE transactions
+  DROP CONSTRAINT blocks_fk;
+
+ALTER TABLE transactions
+  ADD CONSTRAINT fk_test
+FOREIGN KEY (block_id)
+REFERENCES blocks (id);
+
+COMMIT;

db/migrations/1513192766_add_cascade_delete_to_transactions.up.sql

@@ -0,0 +1,12 @@
+BEGIN;
+
+ALTER TABLE transactions
+  DROP CONSTRAINT fk_test;
+
+ALTER TABLE transactions
+  ADD CONSTRAINT blocks_fk
+FOREIGN KEY (block_id)
+REFERENCES blocks (id)
+ON DELETE CASCADE;
+
+COMMIT;

db/migrations/1513275969_add_cascade_delete_to_blocks.down.sql

@@ -0,0 +1,11 @@
+BEGIN;
+
+ALTER TABLE blocks
+  DROP CONSTRAINT node_fk;
+
+ALTER TABLE blocks
+  ADD CONSTRAINT node_fk
+FOREIGN KEY (node_id)
+REFERENCES nodes (id);
+
+COMMIT;

db/migrations/1513275969_add_cascade_delete_to_blocks.up.sql

@@ -0,0 +1,12 @@
+BEGIN;
+
+ALTER TABLE blocks
+  DROP CONSTRAINT node_fk;
+
+ALTER TABLE blocks
+  ADD CONSTRAINT node_fk
+FOREIGN KEY (node_id)
+REFERENCES nodes (id)
+ON DELETE CASCADE;
+
+COMMIT;

db/schema.sql

@@ -331,11 +331,11 @@ CREATE INDEX block_number_index ON blocks USING btree (block_number);
 
 
 --
--- Name: transactions fk_test; Type: FK CONSTRAINT; Schema: public; Owner: -
+-- Name: transactions blocks_fk; Type: FK CONSTRAINT; Schema: public; Owner: -
 --
 
 ALTER TABLE ONLY transactions
-    ADD CONSTRAINT fk_test FOREIGN KEY (block_id) REFERENCES blocks(id);
+    ADD CONSTRAINT blocks_fk FOREIGN KEY (block_id) REFERENCES blocks(id) ON DELETE CASCADE;
 
 
 --
@@ -343,7 +343,7 @@ ALTER TABLE ONLY transactions
 --
 
 ALTER TABLE ONLY blocks
-    ADD CONSTRAINT node_fk FOREIGN KEY (node_id) REFERENCES nodes(id);
+    ADD CONSTRAINT node_fk FOREIGN KEY (node_id) REFERENCES nodes(id) ON DELETE CASCADE;
 
 
 --

integration_test/geth_blockchain_test.go

@@ -1,6 +1,9 @@
 package integration_test
 
 import (
+	"io/ioutil"
+	"log"
+
 	"github.com/8thlight/vulcanizedb/pkg/blockchain_listener"
 	"github.com/8thlight/vulcanizedb/pkg/config"
 	"github.com/8thlight/vulcanizedb/pkg/core"
@@ -10,6 +13,10 @@ import (
 	. "github.com/onsi/gomega"
 )
 
+func init() {
+	log.SetOutput(ioutil.Discard)
+}
+
 var _ = Describe("Reading from the Geth blockchain", func() {
 
 	var listener blockchain_listener.BlockchainListener

pkg/contract_summary/summary_test.go

@@ -63,7 +63,7 @@ var _ = Describe("The contract summary", func() {
 					{To: "0x123"},
 				},
 			}
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 			blockchain := fakes.NewBlockchain()
 
 			contractSummary, _ := NewCurrentContractSummary(blockchain, repository, "0x123")
@@ -81,7 +81,7 @@ var _ = Describe("The contract summary", func() {
 					{Hash: "TRANSACTION1", To: "0x123"},
 				},
 			}
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 			blockchain := fakes.NewBlockchain()
 
 			contractSummary, _ := NewCurrentContractSummary(blockchain, repository, "0x123")

pkg/geth/geth_blockchain.go

@@ -1,10 +1,10 @@
 package geth
 
 import (
-	"fmt"
-
 	"math/big"
 
+	"log"
+
 	"github.com/8thlight/vulcanizedb/pkg/core"
 	"github.com/8thlight/vulcanizedb/pkg/geth/node"
 	"github.com/ethereum/go-ethereum"
@@ -61,7 +61,7 @@ func NewGethBlockchain(ipcPath string) *GethBlockchain {
 
 func (blockchain *GethBlockchain) SubscribeToBlocks(blocks chan core.Block) {
 	blockchain.outputBlocks = blocks
-	fmt.Println("SubscribeToBlocks")
+	log.Println("SubscribeToBlocks")
 	inputHeaders := make(chan *types.Header, 10)
 	myContext := context.Background()
 	blockchain.readGethHeaders = inputHeaders

pkg/history/populate_blocks.go

@@ -5,11 +5,43 @@ import (
 	"github.com/8thlight/vulcanizedb/pkg/repositories"
 )
 
-func PopulateBlocks(blockchain core.Blockchain, repository repositories.Repository, startingBlockNumber int64) int {
+type Window struct {
-	blockNumbers := repository.MissingBlockNumbers(startingBlockNumber, repository.MaxBlockNumber())
+	LowerBound     int
+	UpperBound     int
+	MaxBlockNumber int
+}
+
+func (window Window) Size() int {
+	return int(window.UpperBound - window.LowerBound)
+}
+
+func PopulateMissingBlocks(blockchain core.Blockchain, repository repositories.Repository, startingBlockNumber int64) int {
+	blockRange := repository.MissingBlockNumbers(startingBlockNumber, repository.MaxBlockNumber())
+	updateBlockRange(blockchain, repository, blockRange)
+	return len(blockRange)
+}
+
+func UpdateBlocksWindow(blockchain core.Blockchain, repository repositories.Repository, windowSize int) Window {
+	maxBlockNumber := repository.MaxBlockNumber()
+	upperBound := repository.MaxBlockNumber() - int64(2)
+	lowerBound := upperBound - int64(windowSize)
+	blockRange := MakeRange(lowerBound, upperBound)
+	updateBlockRange(blockchain, repository, blockRange)
+	return Window{int(lowerBound), int(upperBound), int(maxBlockNumber)}
+}
+
+func updateBlockRange(blockchain core.Blockchain, repository repositories.Repository, blockNumbers []int64) int {
 	for _, blockNumber := range blockNumbers {
 		block := blockchain.GetBlockByNumber(blockNumber)
-		repository.CreateBlock(block)
+		repository.CreateOrUpdateBlock(block)
 	}
 	return len(blockNumbers)
 }
+
+func MakeRange(min, max int64) []int64 {
+	a := make([]int64, max-min)
+	for i := range a {
+		a[i] = min + int64(i)
+	}
+	return a
+}

pkg/history/populate_blocks_test.go

@@ -15,16 +15,16 @@ var _ = Describe("Populating blocks", func() {
 		blocks := []core.Block{{Number: 1, Hash: "x012343"}}
 		blockchain := fakes.NewBlockchainWithBlocks(blocks)
 		repository := repositories.NewInMemory()
-		repository.CreateBlock(core.Block{Number: 2})
+		repository.CreateOrUpdateBlock(core.Block{Number: 2})
 
-		history.PopulateBlocks(blockchain, repository, 1)
+		history.PopulateMissingBlocks(blockchain, repository, 1)
 
 		block, err := repository.FindBlockByNumber(1)
 		Expect(err).ToNot(HaveOccurred())
 		Expect(block.Hash).To(Equal("x012343"))
 	})
 
-	It("fills in two missing blocks", func() {
+	It("fills in the three missing blocks (5,8,10)", func() {
 		blockchain := fakes.NewBlockchainWithBlocks([]core.Block{
 			{Number: 4},
 			{Number: 5},
@@ -33,16 +33,16 @@ var _ = Describe("Populating blocks", func() {
 			{Number: 13},
 		})
 		repository := repositories.NewInMemory()
-		repository.CreateBlock(core.Block{Number: 1})
+		repository.CreateOrUpdateBlock(core.Block{Number: 1})
-		repository.CreateBlock(core.Block{Number: 2})
+		repository.CreateOrUpdateBlock(core.Block{Number: 2})
-		repository.CreateBlock(core.Block{Number: 3})
+		repository.CreateOrUpdateBlock(core.Block{Number: 3})
-		repository.CreateBlock(core.Block{Number: 6})
+		repository.CreateOrUpdateBlock(core.Block{Number: 6})
-		repository.CreateBlock(core.Block{Number: 7})
+		repository.CreateOrUpdateBlock(core.Block{Number: 7})
-		repository.CreateBlock(core.Block{Number: 9})
+		repository.CreateOrUpdateBlock(core.Block{Number: 9})
-		repository.CreateBlock(core.Block{Number: 11})
+		repository.CreateOrUpdateBlock(core.Block{Number: 11})
-		repository.CreateBlock(core.Block{Number: 12})
+		repository.CreateOrUpdateBlock(core.Block{Number: 12})
 
-		history.PopulateBlocks(blockchain, repository, 5)
+		history.PopulateMissingBlocks(blockchain, repository, 5)
 
 		Expect(repository.BlockCount()).To(Equal(11))
 		_, err := repository.FindBlockByNumber(4)
@@ -57,18 +57,47 @@ var _ = Describe("Populating blocks", func() {
 		Expect(err).To(HaveOccurred())
 	})
 
+	It("updates the repository with a range of blocks w/in sliding window ", func() {
+		blockchain := fakes.NewBlockchainWithBlocks([]core.Block{
+			{Number: 1},
+			{Number: 2},
+			{Number: 3},
+			{Number: 4},
+			{Number: 5},
+		})
+		repository := repositories.NewInMemory()
+		repository.CreateOrUpdateBlock(blockchain.GetBlockByNumber(5))
+
+		history.UpdateBlocksWindow(blockchain, repository, 2)
+
+		Expect(repository.BlockCount()).To(Equal(3))
+		Expect(repository.HandleBlockCallCount).To(Equal(3))
+	})
+
+	It("Generates a range of int64", func() {
+		numberOfBlocksCreated := history.MakeRange(0, 5)
+		expected := []int64{0, 1, 2, 3, 4}
+
+		Expect(numberOfBlocksCreated).To(Equal(expected))
+	})
+
 	It("returns the number of blocks created", func() {
 		blockchain := fakes.NewBlockchainWithBlocks([]core.Block{
 			{Number: 4},
 			{Number: 5},
 		})
 		repository := repositories.NewInMemory()
-		repository.CreateBlock(core.Block{Number: 3})
+		repository.CreateOrUpdateBlock(core.Block{Number: 3})
-		repository.CreateBlock(core.Block{Number: 6})
+		repository.CreateOrUpdateBlock(core.Block{Number: 6})
 
-		numberOfBlocksCreated := history.PopulateBlocks(blockchain, repository, 3)
+		numberOfBlocksCreated := history.PopulateMissingBlocks(blockchain, repository, 3)
 
 		Expect(numberOfBlocksCreated).To(Equal(2))
 	})
 
+	It("returns the window size", func() {
+		window := history.Window{1, 3, 10}
+		Expect(window.Size()).To(Equal(2))
+	})
+
 })

pkg/observers/blockchain_db_observer.go

@@ -14,5 +14,5 @@ func NewBlockchainDbObserver(repository repositories.Repository) BlockchainDbObs
 }
 
 func (observer BlockchainDbObserver) NotifyBlockAdded(block core.Block) {
-	observer.repository.CreateBlock(block)
+	observer.repository.CreateOrUpdateBlock(block)
 }

pkg/observers/blockchain_logging_observer.go

@@ -1,18 +1,32 @@
 package observers
 
 import (
-	"fmt"
+	"os"
+	"text/template"
+
 	"time"
 
 	"github.com/8thlight/vulcanizedb/pkg/core"
 )
 
+const blockAddedTemplate = `
+    New block was added: {{.Number}}
+    Time: {{.Time | unix_time}}
+    Gas Limit: {{.GasLimit}}
+    Gas Used: {{.GasUsed}}
+    Number of Transactions {{.Transactions | len}}
+
+`
+
+var funcMap = template.FuncMap{
+	"unix_time": func(n int64) time.Time {
+		return time.Unix(n, 0)
+	},
+}
+var tmp = template.Must(template.New("window").Funcs(funcMap).Parse(blockAddedTemplate))
+
 type BlockchainLoggingObserver struct{}
 
 func (blockchainObserver BlockchainLoggingObserver) NotifyBlockAdded(block core.Block) {
-	fmt.Printf("New block was added: %d\n"+
+	tmp.Execute(os.Stdout, block)
-		"\tTime: %v\n"+
-		"\tGas Limit: %d\n"+
-		"\tGas Used: %d\n"+
-		"\tNumber of Transactions %d\n", block.Number, time.Unix(block.Time, 0), block.GasLimit, block.GasUsed, len(block.Transactions))
 }

pkg/repositories/in_memory.go

@@ -7,9 +7,10 @@ import (
 )
 
 type InMemory struct {
-	blocks    map[int64]core.Block
+	blocks               map[int64]core.Block
-	contracts map[string]core.Contract
+	contracts            map[string]core.Contract
-	logs      map[string][]core.Log
+	logs                 map[string][]core.Log
+	HandleBlockCallCount int
 }
 
 func (repository *InMemory) CreateLogs(logs []core.Log) error {
@@ -70,13 +71,15 @@ func (repository *InMemory) MissingBlockNumbers(startingBlockNumber int64, endin
 
 func NewInMemory() *InMemory {
 	return &InMemory{
-		blocks:    make(map[int64]core.Block),
+		HandleBlockCallCount: 0,
-		contracts: make(map[string]core.Contract),
+		blocks:               make(map[int64]core.Block),
-		logs:      make(map[string][]core.Log),
+		contracts:            make(map[string]core.Contract),
+		logs:                 make(map[string][]core.Log),
 	}
 }
 
-func (repository *InMemory) CreateBlock(block core.Block) error {
+func (repository *InMemory) CreateOrUpdateBlock(block core.Block) error {
+	repository.HandleBlockCallCount++
 	repository.blocks[block.Number] = block
 	return nil
 }

pkg/repositories/postgres.go

@@ -15,6 +15,8 @@ import (
 	_ "github.com/lib/pq"
 )
 
+type BlockStatus int
+
 type Postgres struct {
 	Db     *sqlx.DB
 	node   core.Node
@@ -23,6 +25,7 @@ type Postgres struct {
 
 var (
 	ErrDBInsertFailed     = errors.New("postgres: insert failed")
+	ErrDBDeleteFailed     = errors.New("postgres: delete failed")
 	ErrDBConnectionFailed = errors.New("postgres: db connection failed")
 	ErrUnableToSetNode    = errors.New("postgres: unable to set node")
 )
@@ -134,8 +137,10 @@ func (repository Postgres) CreateContract(contract core.Contract) error {
 func (repository Postgres) ContractExists(contractHash string) bool {
 	var exists bool
 	repository.Db.QueryRow(
-		`SELECT exists(SELECT 1 FROM watched_contracts WHERE contract_hash=$1)
+		`SELECT exists(
-                FROM watched_contracts`, contractHash).Scan(&exists)
+                   SELECT 1
+                   FROM watched_contracts
+                   WHERE contract_hash = $1)`, contractHash).Scan(&exists)
 	return exists
 }
 
@@ -205,9 +210,41 @@ func (repository Postgres) BlockCount() int {
 	return count
 }
 
-func (repository Postgres) CreateBlock(block core.Block) error {
+func (repository Postgres) getBlockHash(block core.Block) (string, bool) {
-	tx, _ := repository.Db.BeginTx(context.Background(), nil)
+	var retrievedBlockHash string
+	repository.Db.Get(&retrievedBlockHash,
+		`SELECT block_hash
+			   FROM blocks
+			   WHERE block_number = $1 AND node_id = $2`,
+		block.Number, repository.nodeId)
+	return retrievedBlockHash, blockExists(retrievedBlockHash)
+}
+
+func blockExists(retrievedBlockHash string) bool {
+	return retrievedBlockHash != ""
+}
+
+func (repository Postgres) CreateOrUpdateBlock(block core.Block) error {
+	var err error
+	retrievedBlockHash, ok := repository.getBlockHash(block)
+	if !ok {
+		err = repository.insertBlock(block)
+		return err
+	}
+	if ok && retrievedBlockHash != block.Hash {
+		err = repository.removeBlock(block.Number)
+		if err != nil {
+			return err
+		}
+		err = repository.insertBlock(block)
+		return err
+	}
+	return nil
+}
+
+func (repository Postgres) insertBlock(block core.Block) error {
 	var blockId int64
+	tx, _ := repository.Db.BeginTx(context.Background(), nil)
 	err := tx.QueryRow(
 		`INSERT INTO blocks
 			    (node_id, block_number, block_gaslimit, block_gasused, block_time, block_difficulty, block_hash, block_nonce, block_parenthash, block_size, uncle_hash)
@@ -228,6 +265,18 @@ func (repository Postgres) CreateBlock(block core.Block) error {
 	return nil
 }
 
+func (repository Postgres) removeBlock(blockNumber int64) error {
+	_, err := repository.Db.Exec(
+		`DELETE FROM
+				blocks
+				WHERE block_number=$1 AND node_id=$2`,
+		blockNumber, repository.nodeId)
+	if err != nil {
+		return ErrDBDeleteFailed
+	}
+	return nil
+}
+
 func (repository Postgres) createTransactions(tx *sql.Tx, blockId int64, transactions []core.Transaction) error {
 	for _, transaction := range transactions {
 		_, err := tx.Exec(

pkg/repositories/postgres_test.go

@@ -4,6 +4,9 @@ import (
 	"fmt"
 	"strings"
 
+	"io/ioutil"
+	"log"
+
 	"github.com/8thlight/vulcanizedb/pkg/config"
 	"github.com/8thlight/vulcanizedb/pkg/core"
 	"github.com/8thlight/vulcanizedb/pkg/repositories"
@@ -14,6 +17,10 @@ import (
 	. "github.com/onsi/gomega"
 )
 
+func init() {
+	log.SetOutput(ioutil.Discard)
+}
+
 var _ = Describe("Postgres repository", func() {
 
 	It("connects to the database", func() {
@@ -43,7 +50,7 @@ var _ = Describe("Postgres repository", func() {
 		node := core.Node{GenesisBlock: "GENESIS", NetworkId: 1}
 		repository, _ := repositories.NewPostgres(cfg.Database, node)
 
-		err1 := repository.CreateBlock(badBlock)
+		err1 := repository.CreateOrUpdateBlock(badBlock)
 		savedBlock, err2 := repository.FindBlockByNumber(123)
 
 		Expect(err1).To(HaveOccurred())
@@ -97,7 +104,7 @@ var _ = Describe("Postgres repository", func() {
 		node := core.Node{GenesisBlock: "GENESIS", NetworkId: 1}
 		repository, _ := repositories.NewPostgres(cfg.Database, node)
 
-		err1 := repository.CreateBlock(block)
+		err1 := repository.CreateOrUpdateBlock(block)
 		savedBlock, err2 := repository.FindBlockByNumber(123)
 
 		Expect(err1).To(HaveOccurred())

pkg/repositories/repository.go

@@ -3,7 +3,7 @@ package repositories
 import "github.com/8thlight/vulcanizedb/pkg/core"
 
 type Repository interface {
-	CreateBlock(block core.Block) error
+	CreateOrUpdateBlock(block core.Block) error
 	BlockCount() int
 	FindBlockByNumber(blockNumber int64) (core.Block, error)
 	MaxBlockNumber() int64

pkg/repositories/testing/helpers.go

@@ -33,7 +33,7 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 		It("increments the block count", func() {
 			block := core.Block{Number: 123}
 
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 
 			Expect(repository.BlockCount()).To(Equal(1))
 		})
@@ -42,7 +42,7 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 			block := core.Block{
 				Number: 123,
 			}
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 			nodeTwo := core.Node{
 				GenesisBlock: "0x456",
 				NetworkId:    1,
@@ -77,7 +77,7 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 				UncleHash:  uncleHash,
 			}
 
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 
 			savedBlock, err := repository.FindBlockByNumber(blockNumber)
 			Expect(err).NotTo(HaveOccurred())
@@ -105,7 +105,7 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 				Transactions: []core.Transaction{{}},
 			}
 
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 
 			savedBlock, _ := repository.FindBlockByNumber(123)
 			Expect(len(savedBlock.Transactions)).To(Equal(1))
@@ -117,12 +117,60 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 				Transactions: []core.Transaction{{}, {}},
 			}
 
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 
 			savedBlock, _ := repository.FindBlockByNumber(123)
 			Expect(len(savedBlock.Transactions)).To(Equal(2))
 		})
 
+		It(`replaces blocks and transactions associated to the block
+			when a more new block is in conflict (same block number + nodeid)`, func() {
+			blockOne := core.Block{
+				Number:       123,
+				Hash:         "xabc",
+				Transactions: []core.Transaction{{Hash: "x123"}, {Hash: "x345"}},
+			}
+			blockTwo := core.Block{
+				Number:       123,
+				Hash:         "xdef",
+				Transactions: []core.Transaction{{Hash: "x678"}, {Hash: "x9ab"}},
+			}
+
+			repository.CreateOrUpdateBlock(blockOne)
+			repository.CreateOrUpdateBlock(blockTwo)
+
+			savedBlock, _ := repository.FindBlockByNumber(123)
+			Expect(len(savedBlock.Transactions)).To(Equal(2))
+			Expect(savedBlock.Transactions[0].Hash).To(Equal("x678"))
+			Expect(savedBlock.Transactions[1].Hash).To(Equal("x9ab"))
+		})
+
+		It(`does not replace blocks when block number is not unique
+			     but block number + node id is`, func() {
+			blockOne := core.Block{
+				Number:       123,
+				Transactions: []core.Transaction{{Hash: "x123"}, {Hash: "x345"}},
+			}
+			blockTwo := core.Block{
+				Number:       123,
+				Transactions: []core.Transaction{{Hash: "x678"}, {Hash: "x9ab"}},
+			}
+			repository.CreateOrUpdateBlock(blockOne)
+			nodeTwo := core.Node{
+				GenesisBlock: "0x456",
+				NetworkId:    1,
+			}
+			repositoryTwo := buildRepository(nodeTwo)
+
+			repository.CreateOrUpdateBlock(blockOne)
+			repositoryTwo.CreateOrUpdateBlock(blockTwo)
+			retrievedBlockOne, _ := repository.FindBlockByNumber(123)
+			retrievedBlockTwo, _ := repositoryTwo.FindBlockByNumber(123)
+
+			Expect(retrievedBlockOne.Transactions[0].Hash).To(Equal("x123"))
+			Expect(retrievedBlockTwo.Transactions[0].Hash).To(Equal("x678"))
+		})
+
 		It("saves the attributes associated to a transaction", func() {
 			gasLimit := int64(5000)
 			gasPrice := int64(3)
@@ -144,7 +192,7 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 				Transactions: []core.Transaction{transaction},
 			}
 
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 
 			savedBlock, _ := repository.FindBlockByNumber(123)
 			Expect(len(savedBlock.Transactions)).To(Equal(1))
@@ -162,41 +210,41 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 
 	Describe("The missing block numbers", func() {
 		It("is empty the starting block number is the highest known block number", func() {
-			repository.CreateBlock(core.Block{Number: 1})
+			repository.CreateOrUpdateBlock(core.Block{Number: 1})
 
 			Expect(len(repository.MissingBlockNumbers(1, 1))).To(Equal(0))
 		})
 
 		It("is the only missing block number", func() {
-			repository.CreateBlock(core.Block{Number: 2})
+			repository.CreateOrUpdateBlock(core.Block{Number: 2})
 
 			Expect(repository.MissingBlockNumbers(1, 2)).To(Equal([]int64{1}))
 		})
 
 		It("is both missing block numbers", func() {
-			repository.CreateBlock(core.Block{Number: 3})
+			repository.CreateOrUpdateBlock(core.Block{Number: 3})
 
 			Expect(repository.MissingBlockNumbers(1, 3)).To(Equal([]int64{1, 2}))
 		})
 
 		It("goes back to the starting block number", func() {
-			repository.CreateBlock(core.Block{Number: 6})
+			repository.CreateOrUpdateBlock(core.Block{Number: 6})
 
 			Expect(repository.MissingBlockNumbers(4, 6)).To(Equal([]int64{4, 5}))
 		})
 
 		It("only includes missing block numbers", func() {
-			repository.CreateBlock(core.Block{Number: 4})
+			repository.CreateOrUpdateBlock(core.Block{Number: 4})
-			repository.CreateBlock(core.Block{Number: 6})
+			repository.CreateOrUpdateBlock(core.Block{Number: 6})
 
 			Expect(repository.MissingBlockNumbers(4, 6)).To(Equal([]int64{5}))
 		})
 
 		It("is a list with multiple gaps", func() {
-			repository.CreateBlock(core.Block{Number: 4})
+			repository.CreateOrUpdateBlock(core.Block{Number: 4})
-			repository.CreateBlock(core.Block{Number: 5})
+			repository.CreateOrUpdateBlock(core.Block{Number: 5})
-			repository.CreateBlock(core.Block{Number: 8})
+			repository.CreateOrUpdateBlock(core.Block{Number: 8})
-			repository.CreateBlock(core.Block{Number: 10})
+			repository.CreateOrUpdateBlock(core.Block{Number: 10})
 
 			Expect(repository.MissingBlockNumbers(3, 10)).To(Equal([]int64{3, 6, 7, 9}))
 		})
@@ -206,8 +254,8 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 		})
 
 		It("only returns requested range even when other gaps exist", func() {
-			repository.CreateBlock(core.Block{Number: 3})
+			repository.CreateOrUpdateBlock(core.Block{Number: 3})
-			repository.CreateBlock(core.Block{Number: 8})
+			repository.CreateOrUpdateBlock(core.Block{Number: 8})
 
 			Expect(repository.MissingBlockNumbers(1, 5)).To(Equal([]int64{1, 2, 4, 5}))
 		})
@@ -215,14 +263,14 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 
 	Describe("The max block numbers", func() {
 		It("returns the block number when a single block", func() {
-			repository.CreateBlock(core.Block{Number: 1})
+			repository.CreateOrUpdateBlock(core.Block{Number: 1})
 
 			Expect(repository.MaxBlockNumber()).To(Equal(int64(1)))
 		})
 
 		It("returns highest known block number when multiple blocks", func() {
-			repository.CreateBlock(core.Block{Number: 1})
+			repository.CreateOrUpdateBlock(core.Block{Number: 1})
-			repository.CreateBlock(core.Block{Number: 10})
+			repository.CreateOrUpdateBlock(core.Block{Number: 10})
 
 			Expect(repository.MaxBlockNumber()).To(Equal(int64(10)))
 		})
@@ -261,7 +309,7 @@ func AssertRepositoryBehavior(buildRepository func(node core.Node) repositories.
 					{Hash: "TRANSACTION3", To: "x123"},
 				},
 			}
-			repository.CreateBlock(block)
+			repository.CreateOrUpdateBlock(block)
 
 			repository.CreateContract(core.Contract{Hash: "x123"})
 			contract, err := repository.FindContract("x123")