Merge pull request #12 from vulcanize/VDB-392-fix-io-error-propagation

VDB-392 Fix IO error propagation

cmd/lightSync.go

@@ -62,7 +62,9 @@ func init() {
 func backFillAllHeaders(blockchain core.BlockChain, headerRepository datastore.HeaderRepository, missingBlocksPopulated chan int, startingBlockNumber int64) {
 	populated, err := history.PopulateMissingHeaders(blockchain, headerRepository, startingBlockNumber)
 	if err != nil {
-		log.Fatal("Error populating headers: ", err)
+		// TODO Lots of possible errors in the call stack above. If errors occur, we still put
+		// 0 in the channel, triggering another round
+		log.Error("backfillAllHeaders: Error populating headers: ", err)
 	}
 	missingBlocksPopulated <- populated
 }
@@ -84,7 +86,7 @@ func lightSync() {
 		case <-ticker.C:
 			window, err := validator.ValidateHeaders()
 			if err != nil {
-				log.Error("ValidateHeaders failed in lightSync: ", err)
+				log.Error("lightSync: ValidateHeaders failed: ", err)
 			}
 			log.Info(window.GetString())
 		case n := <-missingBlocksPopulated:
@@ -97,11 +99,14 @@ func lightSync() {
 }
 
 func validateArgs(blockChain *geth.BlockChain) {
-	lastBlock := blockChain.LastBlock().Int64()
+	lastBlock, err := blockChain.LastBlock()
-	if lastBlock == 0 {
+	if err != nil {
+		log.Error("validateArgs: Error getting last block: ", err)
+	}
+	if lastBlock.Int64() == 0 {
 		log.Fatal("geth initial: state sync not finished")
 	}
-	if startingBlockNumber > lastBlock {
+	if startingBlockNumber > lastBlock.Int64() {
 		log.Fatal("starting block number > current block number")
 	}
 }

cmd/sync.go

@@ -60,7 +60,11 @@ func init() {
 }
 
 func backFillAllBlocks(blockchain core.BlockChain, blockRepository datastore.BlockRepository, missingBlocksPopulated chan int, startingBlockNumber int64) {
-	missingBlocksPopulated <- history.PopulateMissingBlocks(blockchain, blockRepository, startingBlockNumber)
+	populated, err := history.PopulateMissingBlocks(blockchain, blockRepository, startingBlockNumber)
+	if err != nil {
+		log.Error("backfillAllBlocks: error in populateMissingBlocks: ", err)
+	}
+	missingBlocksPopulated <- populated
 }
 
 func sync() {
@@ -68,12 +72,15 @@ func sync() {
 	defer ticker.Stop()
 
 	blockChain := getBlockChain()
-	lastBlock := blockChain.LastBlock().Int64()
+	lastBlock, err := blockChain.LastBlock()
-	if lastBlock == 0 {
+	if err != nil {
+		log.Error("sync: Error getting last block: ", err)
+	}
+	if lastBlock.Int64() == 0 {
 		log.Fatal("geth initial: state sync not finished")
 	}
-	if startingBlockNumber > lastBlock {
+	if startingBlockNumber > lastBlock.Int64() {
-		log.Fatal("starting block number > current block number")
+		log.Fatal("sync: starting block number > current block number")
 	}
 
 	db := utils.LoadPostgres(databaseConfig, blockChain.Node())
@@ -85,7 +92,10 @@ func sync() {
 	for {
 		select {
 		case <-ticker.C:
-			window := validator.ValidateBlocks()
+			window, err := validator.ValidateBlocks()
+			if err != nil {
+				log.Error("sync: error in validateBlocks: ", err)
+			}
 			log.Info(window.GetString())
 		case <-missingBlocksPopulated:
 			go backFillAllBlocks(blockChain, blockRepository, missingBlocksPopulated, startingBlockNumber)

environments/staging.toml

@@ -1,4 +1,8 @@
 [database]
+    name = "vulcanize_public"
+    hostname = "localhost"
+    user = "vulcanize"
+    password = "vulcanize"
     port = 5432
 
 [client]

integration_test/geth_blockchain_test.go

@@ -48,9 +48,13 @@ var _ = Describe("Reading from the Geth blockchain", func() {
 
 	It("reads two blocks", func(done Done) {
 		blocks := fakes.NewMockBlockRepository()
-		lastBlock := blockChain.LastBlock()
+		lastBlock, err := blockChain.LastBlock()
+		Expect(err).NotTo(HaveOccurred())
+
 		queriedBlocks := []int64{lastBlock.Int64() - 5, lastBlock.Int64() - 6}
-		history.RetrieveAndUpdateBlocks(blockChain, blocks, queriedBlocks)
+		_, err = history.RetrieveAndUpdateBlocks(blockChain, blocks, queriedBlocks)
+		Expect(err).NotTo(HaveOccurred())
+
 		blocks.AssertCreateOrUpdateBlocksCallCountAndBlockNumbersEquals(2, []int64{lastBlock.Int64() - 5, lastBlock.Int64() - 6})
 		close(done)
 	}, 30)
@@ -60,8 +64,9 @@ var _ = Describe("Reading from the Geth blockchain", func() {
 		Expect(err).ToNot(HaveOccurred())
 		firstBlock, err := blockChain.GetBlockByNumber(int64(1))
 		Expect(err).ToNot(HaveOccurred())
-		lastBlockNumber := blockChain.LastBlock()
+		lastBlockNumber, err := blockChain.LastBlock()
 
+		Expect(err).NotTo(HaveOccurred())
 		Expect(genesisBlock.Number).To(Equal(int64(0)))
 		Expect(firstBlock.Number).To(Equal(int64(1)))
 		Expect(lastBlockNumber.Int64()).To(BeNumerically(">", 0))

pkg/core/blockchain.go

@@ -30,7 +30,7 @@ type BlockChain interface {
 	GetHeaderByNumbers(blockNumbers []int64) ([]Header, error)
 	GetLogs(contract Contract, startingBlockNumber *big.Int, endingBlockNumber *big.Int) ([]Log, error)
 	GetEthLogsWithCustomQuery(query ethereum.FilterQuery) ([]types.Log, error)
-	LastBlock() *big.Int
+	LastBlock() (*big.Int, error)
 	Node() Node
 }
 

pkg/datastore/ethereum/database.go

@@ -18,6 +18,7 @@ package ethereum
 
 import (
 	"fmt"
+	"github.com/sirupsen/logrus"
 
 	"github.com/ethereum/go-ethereum/core/types"
 	"github.com/ethereum/go-ethereum/ethdb"
@@ -37,6 +38,7 @@ func CreateDatabase(config DatabaseConfig) (Database, error) {
 	case Level:
 		levelDBConnection, err := ethdb.NewLDBDatabase(config.Path, 128, 1024)
 		if err != nil {
+			logrus.Error("CreateDatabase: error connecting to new LDBD: ", err)
 			return nil, err
 		}
 		levelDBReader := level.NewLevelDatabaseReader(levelDBConnection)

pkg/datastore/postgres/postgres_test.go

@@ -134,8 +134,9 @@ var _ = Describe("Postgres DB", func() {
 		err := logRepository.CreateLogs([]core.Log{badLog}, 123)
 
 		Expect(err).ToNot(BeNil())
-		savedBlock := logRepository.GetLogs("x123", 1)
+		savedBlock, err := logRepository.GetLogs("x123", 1)
 		Expect(savedBlock).To(BeNil())
+		Expect(err).To(Not(HaveOccurred()))
 	})
 
 	It("does not commit block or transactions if transaction is invalid", func() {

pkg/datastore/postgres/repositories/block_repository.go

@@ -43,12 +43,14 @@ func NewBlockRepository(database *postgres.DB) *BlockRepository {
 	return &BlockRepository{database: database}
 }
 
-func (blockRepository BlockRepository) SetBlocksStatus(chainHead int64) {
+func (blockRepository BlockRepository) SetBlocksStatus(chainHead int64) error {
 	cutoff := chainHead - blocksFromHeadBeforeFinal
-	blockRepository.database.Exec(`
+	_, err := blockRepository.database.Exec(`
                   UPDATE blocks SET is_final = TRUE
                   WHERE is_final = FALSE AND number < $1`,
 		cutoff)
+
+	return err
 }
 
 func (blockRepository BlockRepository) CreateOrUpdateBlock(block core.Block) (int64, error) {
@@ -70,7 +72,7 @@ func (blockRepository BlockRepository) CreateOrUpdateBlock(block core.Block) (in
 
 func (blockRepository BlockRepository) MissingBlockNumbers(startingBlockNumber int64, highestBlockNumber int64, nodeId string) []int64 {
 	numbers := make([]int64, 0)
-	blockRepository.database.Select(&numbers,
+	err := blockRepository.database.Select(&numbers,
 		`SELECT all_block_numbers
           FROM (
               SELECT generate_series($1::INT, $2::INT) AS all_block_numbers) series
@@ -79,6 +81,9 @@ func (blockRepository BlockRepository) MissingBlockNumbers(startingBlockNumber i
 		  ) `,
 		startingBlockNumber,
 		highestBlockNumber, nodeId)
+	if err != nil {
+		log.Error("MissingBlockNumbers: error getting blocks: ", err)
+	}
 	return numbers
 }
 
@@ -108,6 +113,7 @@ func (blockRepository BlockRepository) GetBlock(blockNumber int64) (core.Block,
 		case sql.ErrNoRows:
 			return core.Block{}, datastore.ErrBlockDoesNotExist(blockNumber)
 		default:
+			log.Error("GetBlock: error loading blocks: ", err)
 			return savedBlock, err
 		}
 	}
@@ -202,6 +208,7 @@ func (blockRepository BlockRepository) createReceipt(tx *sql.Tx, blockId int64,
                RETURNING id`,
 		receipt.ContractAddress, receipt.TxHash, receipt.CumulativeGasUsed, receipt.GasUsed, receipt.StateRoot, receipt.Status, blockId).Scan(&receiptId)
 	if err != nil {
+		log.Error("createReceipt: error inserting receipt: ", err)
 		return receiptId, err
 	}
 	return receiptId, nil
@@ -256,6 +263,7 @@ func (blockRepository BlockRepository) loadBlock(blockRows *sqlx.Row) (core.Bloc
 	var block b
 	err := blockRows.StructScan(&block)
 	if err != nil {
+		log.Error("loadBlock: error loading block: ", err)
 		return core.Block{}, err
 	}
 	transactionRows, err := blockRepository.database.Queryx(`
@@ -271,6 +279,7 @@ func (blockRepository BlockRepository) loadBlock(blockRows *sqlx.Row) (core.Bloc
             WHERE block_id = $1
             ORDER BY hash`, block.ID)
 	if err != nil {
+		log.Error("loadBlock: error fetting transactions: ", err)
 		return core.Block{}, err
 	}
 	block.Transactions = blockRepository.LoadTransactions(transactionRows)

pkg/datastore/postgres/repositories/contract_repository.go

@@ -47,14 +47,17 @@ func (contractRepository ContractRepository) CreateContract(contract core.Contra
 	return nil
 }
 
-func (contractRepository ContractRepository) ContractExists(contractHash string) bool {
+func (contractRepository ContractRepository) ContractExists(contractHash string) (bool, error) {
 	var exists bool
-	contractRepository.DB.QueryRow(
+	err := contractRepository.DB.QueryRow(
 		`SELECT exists(
                    SELECT 1
                    FROM watched_contracts
                    WHERE contract_hash = $1)`, contractHash).Scan(&exists)
-	return exists
+	if err != nil {
+		return false, err
+	}
+	return exists, nil
 }
 
 func (contractRepository ContractRepository) GetContract(contractHash string) (core.Contract, error) {
@@ -66,12 +69,15 @@ func (contractRepository ContractRepository) GetContract(contractHash string) (c
 	if err == sql.ErrNoRows {
 		return core.Contract{}, datastore.ErrContractDoesNotExist(contractHash)
 	}
-	savedContract := contractRepository.addTransactions(core.Contract{Hash: hash, Abi: abi})
+	savedContract, err := contractRepository.addTransactions(core.Contract{Hash: hash, Abi: abi})
+	if err != nil {
+		return core.Contract{}, err
+	}
 	return savedContract, nil
 }
 
-func (contractRepository ContractRepository) addTransactions(contract core.Contract) core.Contract {
+func (contractRepository ContractRepository) addTransactions(contract core.Contract) (core.Contract, error) {
-	transactionRows, _ := contractRepository.DB.Queryx(`
+	transactionRows, err := contractRepository.DB.Queryx(`
             SELECT hash,
                    nonce,
                    tx_to,
@@ -83,8 +89,11 @@ func (contractRepository ContractRepository) addTransactions(contract core.Contr
             FROM transactions
             WHERE tx_to = $1
             ORDER BY block_id DESC`, contract.Hash)
+	if err != nil {
+		return core.Contract{}, err
+	}
 	blockRepository := &BlockRepository{contractRepository.DB}
 	transactions := blockRepository.LoadTransactions(transactionRows)
 	savedContract := core.Contract{Hash: contract.Hash, Transactions: transactions, Abi: contract.Abi}
-	return savedContract
+	return savedContract, nil
 }

pkg/datastore/postgres/repositories/header_repository.go

@@ -42,6 +42,7 @@ func (repository HeaderRepository) CreateOrUpdateHeader(header core.Header) (int
 		if headerDoesNotExist(err) {
 			return repository.insertHeader(header)
 		}
+		log.Error("CreateOrUpdateHeader: error getting header hash: ", err)
 		return 0, err
 	}
 	if headerMustBeReplaced(hash, header) {
@@ -54,6 +55,7 @@ func (repository HeaderRepository) GetHeader(blockNumber int64) (core.Header, er
 	var header core.Header
 	err := repository.database.Get(&header, `SELECT id, block_number, hash, raw, block_timestamp FROM headers WHERE block_number = $1 AND eth_node_fingerprint = $2`,
 		blockNumber, repository.database.Node.ID)
+	log.Error("GetHeader: error getting headers: ", err)
 	return header, err
 }
 
@@ -74,18 +76,6 @@ func (repository HeaderRepository) MissingBlockNumbers(startingBlockNumber, endi
 	return numbers, nil
 }
 
-func (repository HeaderRepository) HeaderExists(blockNumber int64) (bool, error) {
-	_, err := repository.GetHeader(blockNumber)
-	if err != nil {
-		if headerDoesNotExist(err) {
-			return false, nil
-		}
-		return false, err
-	}
-
-	return true, nil
-}
-
 func headerMustBeReplaced(hash string, header core.Header) bool {
 	return hash != header.Hash
 }
@@ -98,6 +88,7 @@ func (repository HeaderRepository) getHeaderHash(header core.Header) (string, er
 	var hash string
 	err := repository.database.Get(&hash, `SELECT hash FROM headers WHERE block_number = $1 AND eth_node_fingerprint = $2`,
 		header.BlockNumber, repository.database.Node.ID)
+	log.Error("getHeaderHash: error getting headers: ", err)
 	return hash, err
 }
 
@@ -106,6 +97,9 @@ func (repository HeaderRepository) insertHeader(header core.Header) (int64, erro
 	err := repository.database.QueryRowx(
 		`INSERT INTO public.headers (block_number, hash, block_timestamp, raw, eth_node_id, eth_node_fingerprint) VALUES ($1, $2, $3::NUMERIC, $4, $5, $6) RETURNING id`,
 		header.BlockNumber, header.Hash, header.Timestamp, header.Raw, repository.database.NodeID, repository.database.Node.ID).Scan(&headerId)
+	if err != nil {
+		log.Error("insertHeader: error inserting header: ", err)
+	}
 	return headerId, err
 }
 
@@ -113,6 +107,7 @@ func (repository HeaderRepository) replaceHeader(header core.Header) (int64, err
 	_, err := repository.database.Exec(`DELETE FROM headers WHERE block_number = $1 AND eth_node_fingerprint = $2`,
 		header.BlockNumber, repository.database.Node.ID)
 	if err != nil {
+		log.Error("replaceHeader: error deleting headers: ", err)
 		return 0, err
 	}
 	return repository.insertHeader(header)

pkg/datastore/postgres/repositories/header_repository_test.go

@@ -273,21 +273,4 @@ var _ = Describe("Block header repository", func() {
 			Expect(missingBlockNumbers).To(ConsistOf([]int64{1, 2, 3, 4, 5}))
 		})
 	})
-
-	Describe("HeaderExists", func() {
-		It("returns true if the header record exists", func() {
-			_, err = repo.CreateOrUpdateHeader(header)
-			Expect(err).NotTo(HaveOccurred())
-
-			result, err := repo.HeaderExists(header.BlockNumber)
-			Expect(err).NotTo(HaveOccurred())
-			Expect(result).To(BeTrue())
-		})
-
-		It("returns false if the header record doesn't exist", func() {
-			result, err := repo.HeaderExists(1)
-			Expect(err).NotTo(HaveOccurred())
-			Expect(result).To(BeFalse())
-		})
-	})
 })

pkg/datastore/postgres/repositories/logs_repository.go

@@ -18,6 +18,7 @@ package repositories
 
 import (
 	"context"
+	"github.com/sirupsen/logrus"
 
 	"database/sql"
 
@@ -39,16 +40,26 @@ func (logRepository LogRepository) CreateLogs(lgs []core.Log, receiptId int64) e
 			tlog.BlockNumber, tlog.Address, tlog.TxHash, tlog.Index, tlog.Topics[0], tlog.Topics[1], tlog.Topics[2], tlog.Topics[3], tlog.Data, receiptId,
 		)
 		if err != nil {
-			tx.Rollback()
+			err = tx.Rollback()
+			if err != nil {
+				logrus.Error("CreateLogs: could not perform rollback: ", err)
+			}
 			return postgres.ErrDBInsertFailed
 		}
 	}
-	tx.Commit()
+	err := tx.Commit()
+	if err != nil {
+		err = tx.Rollback()
+		if err != nil {
+			logrus.Error("CreateLogs: could not perform rollback: ", err)
+		}
+		return postgres.ErrDBInsertFailed
+	}
 	return nil
 }
 
-func (logRepository LogRepository) GetLogs(address string, blockNumber int64) []core.Log {
+func (logRepository LogRepository) GetLogs(address string, blockNumber int64) ([]core.Log, error) {
-	logRows, _ := logRepository.DB.Query(
+	logRows, err := logRepository.DB.Query(
 		`SELECT block_number,
 					  address,
 					  tx_hash,
@@ -61,10 +72,13 @@ func (logRepository LogRepository) GetLogs(address string, blockNumber int64) []
 				FROM logs
 				WHERE address = $1 AND block_number = $2
 				ORDER BY block_number DESC`, address, blockNumber)
+	if err != nil {
+		return []core.Log{}, err
+	}
 	return logRepository.loadLogs(logRows)
 }
 
-func (logRepository LogRepository) loadLogs(logsRows *sql.Rows) []core.Log {
+func (logRepository LogRepository) loadLogs(logsRows *sql.Rows) ([]core.Log, error) {
 	var lgs []core.Log
 	for logsRows.Next() {
 		var blockNumber int64
@@ -73,7 +87,11 @@ func (logRepository LogRepository) loadLogs(logsRows *sql.Rows) []core.Log {
 		var index int64
 		var data string
 		var topics core.Topics
-		logsRows.Scan(&blockNumber, &address, &txHash, &index, &topics[0], &topics[1], &topics[2], &topics[3], &data)
+		err := logsRows.Scan(&blockNumber, &address, &txHash, &index, &topics[0], &topics[1], &topics[2], &topics[3], &data)
+		if err != nil {
+			logrus.Error("loadLogs: Error scanning a row in logRows: ", err)
+			return []core.Log{}, err
+		}
 		lg := core.Log{
 			BlockNumber: blockNumber,
 			TxHash:      txHash,
@@ -86,5 +104,5 @@ func (logRepository LogRepository) loadLogs(logsRows *sql.Rows) []core.Log {
 		}
 		lgs = append(lgs, lg)
 	}
-	return lgs
+	return lgs, nil
 }

pkg/datastore/postgres/repositories/logs_repository_test.go

@@ -56,7 +56,7 @@ var _ = Describe("Logs Repository", func() {
 			Expect(err).NotTo(HaveOccurred())
 			receiptId, err := receiptRepository.CreateReceipt(blockId, core.Receipt{})
 			Expect(err).NotTo(HaveOccurred())
-			logsRepository.CreateLogs([]core.Log{{
+			err = logsRepository.CreateLogs([]core.Log{{
 				BlockNumber: blockNumber,
 				Index:       0,
 				Address:     "x123",
@@ -64,9 +64,11 @@ var _ = Describe("Logs Repository", func() {
 				Topics:      core.Topics{0: "x777", 1: "x888", 2: "x999"},
 				Data:        "xabc",
 			}}, receiptId)
+			Expect(err).NotTo(HaveOccurred())
 
-			log := logsRepository.GetLogs("x123", blockNumber)
+			log, err := logsRepository.GetLogs("x123", blockNumber)
 
+			Expect(err).NotTo(HaveOccurred())
 			Expect(log).NotTo(BeNil())
 			Expect(log[0].BlockNumber).To(Equal(blockNumber))
 			Expect(log[0].Address).To(Equal("x123"))
@@ -79,7 +81,8 @@ var _ = Describe("Logs Repository", func() {
 		})
 
 		It("returns nil if log does not exist", func() {
-			log := logsRepository.GetLogs("x123", 1)
+			log, err := logsRepository.GetLogs("x123", 1)
+			Expect(err).NotTo(HaveOccurred())
 			Expect(log).To(BeNil())
 		})
 
@@ -89,7 +92,8 @@ var _ = Describe("Logs Repository", func() {
 			Expect(err).NotTo(HaveOccurred())
 			receiptId, err := receiptRepository.CreateReceipt(blockId, core.Receipt{})
 			Expect(err).NotTo(HaveOccurred())
-			logsRepository.CreateLogs([]core.Log{{
+
+			err = logsRepository.CreateLogs([]core.Log{{
 				BlockNumber: blockNumber,
 				Index:       0,
 				Address:     "x123",
@@ -97,7 +101,9 @@ var _ = Describe("Logs Repository", func() {
 				Topics:      core.Topics{0: "x777", 1: "x888", 2: "x999"},
 				Data:        "xabc",
 			}}, receiptId)
-			logsRepository.CreateLogs([]core.Log{{
+			Expect(err).NotTo(HaveOccurred())
+
+			err = logsRepository.CreateLogs([]core.Log{{
 				BlockNumber: blockNumber,
 				Index:       1,
 				Address:     "x123",
@@ -105,7 +111,9 @@ var _ = Describe("Logs Repository", func() {
 				Topics:      core.Topics{0: "x111", 1: "x222", 2: "x333"},
 				Data:        "xdef",
 			}}, receiptId)
-			logsRepository.CreateLogs([]core.Log{{
+			Expect(err).NotTo(HaveOccurred())
+
+			err = logsRepository.CreateLogs([]core.Log{{
 				BlockNumber: 2,
 				Index:       0,
 				Address:     "x123",
@@ -113,13 +121,16 @@ var _ = Describe("Logs Repository", func() {
 				Topics:      core.Topics{0: "x777", 1: "x888", 2: "x999"},
 				Data:        "xabc",
 			}}, receiptId)
+			Expect(err).NotTo(HaveOccurred())
 
-			log := logsRepository.GetLogs("x123", blockNumber)
+			log, err := logsRepository.GetLogs("x123", blockNumber)
+			Expect(err).NotTo(HaveOccurred())
 
 			type logIndex struct {
 				blockNumber int64
 				Index       int64
 			}
+
 			var uniqueBlockNumbers []logIndex
 			for _, log := range log {
 				uniqueBlockNumbers = append(uniqueBlockNumbers,
@@ -199,8 +210,9 @@ var _ = Describe("Logs Repository", func() {
 			block := core.Block{Transactions: []core.Transaction{transaction}}
 			_, err := blockRepository.CreateOrUpdateBlock(block)
 			Expect(err).To(Not(HaveOccurred()))
-			retrievedLogs := logsRepository.GetLogs("0x99041f808d598b782d5a3e498681c2452a31da08", 4745407)
+			retrievedLogs, err := logsRepository.GetLogs("0x99041f808d598b782d5a3e498681c2452a31da08", 4745407)
 
+			Expect(err).NotTo(HaveOccurred())
 			expected := logs[1:]
 			Expect(retrievedLogs).To(Equal(expected))
 		})

pkg/datastore/postgres/repositories/receipt_repository.go

@@ -19,6 +19,7 @@ package repositories
 import (
 	"context"
 	"database/sql"
+	"github.com/sirupsen/logrus"
 
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore"
@@ -61,6 +62,9 @@ func createReceipt(receipt core.Receipt, blockId int64, tx *sql.Tx) (int64, erro
 		               RETURNING id`,
 		receipt.ContractAddress, receipt.TxHash, receipt.CumulativeGasUsed, receipt.GasUsed, receipt.StateRoot, receipt.Status, blockId,
 	).Scan(&receiptId)
+	if err != nil {
+		logrus.Error("createReceipt: Error inserting: ", err)
+	}
 	return receiptId, err
 }
 
@@ -90,6 +94,7 @@ func (receiptRepository ReceiptRepository) CreateReceipt(blockId int64, receipt
 		receipt.ContractAddress, receipt.TxHash, receipt.CumulativeGasUsed, receipt.GasUsed, receipt.StateRoot, receipt.Status, blockId).Scan(&receiptId)
 	if err != nil {
 		tx.Rollback()
+		logrus.Warning("CreateReceipt: error inserting receipt: ", err)
 		return receiptId, err
 	}
 	tx.Commit()

pkg/datastore/postgres/repositories/receipts_repository_test.go

@@ -87,14 +87,19 @@ var _ = Describe("Receipts Repository", func() {
 			Expect(err).NotTo(HaveOccurred())
 			Expect(persistedReceiptOne).NotTo(BeNil())
 			Expect(persistedReceiptOne.TxHash).To(Equal(txHashOne))
+
 			persistedReceiptTwo, err := receiptRepository.GetReceipt(txHashTwo)
 			Expect(err).NotTo(HaveOccurred())
 			Expect(persistedReceiptTwo).NotTo(BeNil())
 			Expect(persistedReceiptTwo.TxHash).To(Equal(txHashTwo))
-			persistedAddressOneLogs := logRepository.GetLogs(addressOne, blockNumber)
+
+			persistedAddressOneLogs, err := logRepository.GetLogs(addressOne, blockNumber)
+			Expect(err).NotTo(HaveOccurred())
 			Expect(persistedAddressOneLogs).NotTo(BeNil())
 			Expect(len(persistedAddressOneLogs)).To(Equal(2))
-			persistedAddressTwoLogs := logRepository.GetLogs(addressTwo, blockNumber)
+
+			persistedAddressTwoLogs, err := logRepository.GetLogs(addressTwo, blockNumber)
+			Expect(err).NotTo(HaveOccurred())
 			Expect(persistedAddressTwoLogs).NotTo(BeNil())
 			Expect(len(persistedAddressTwoLogs)).To(Equal(1))
 		})

pkg/datastore/postgres/repositories/watched_events_repository.go

@@ -17,6 +17,7 @@
 package repositories
 
 import (
+	"github.com/sirupsen/logrus"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres"
 )
@@ -28,6 +29,7 @@ type WatchedEventRepository struct {
 func (watchedEventRepository WatchedEventRepository) GetWatchedEvents(name string) ([]*core.WatchedEvent, error) {
 	rows, err := watchedEventRepository.DB.Queryx(`SELECT id, name, block_number, address, tx_hash, index, topic0, topic1, topic2, topic3, data FROM watched_event_logs where name=$1`, name)
 	if err != nil {
+		logrus.Error("GetWatchedEvents: error getting watched events: ", err)
 		return nil, err
 	}
 	defer rows.Close()
@@ -37,11 +39,13 @@ func (watchedEventRepository WatchedEventRepository) GetWatchedEvents(name strin
 		lg := new(core.WatchedEvent)
 		err = rows.StructScan(lg)
 		if err != nil {
+			logrus.Warn("GetWatchedEvents: error scanning log: ", err)
 			return nil, err
 		}
 		lgs = append(lgs, lg)
 	}
 	if err = rows.Err(); err != nil {
+		logrus.Warn("GetWatchedEvents: error scanning logs: ", err)
 		return nil, err
 	}
 	return lgs, nil

pkg/datastore/repository.go

@@ -31,7 +31,7 @@ type BlockRepository interface {
 	CreateOrUpdateBlock(block core.Block) (int64, error)
 	GetBlock(blockNumber int64) (core.Block, error)
 	MissingBlockNumbers(startingBlockNumber, endingBlockNumber int64, nodeID string) []int64
-	SetBlocksStatus(chainHead int64)
+	SetBlocksStatus(chainHead int64) error
 }
 
 var ErrContractDoesNotExist = func(contractHash string) error {
@@ -41,7 +41,7 @@ var ErrContractDoesNotExist = func(contractHash string) error {
 type ContractRepository interface {
 	CreateContract(contract core.Contract) error
 	GetContract(contractHash string) (core.Contract, error)
-	ContractExists(contractHash string) bool
+	ContractExists(contractHash string) (bool, error)
 }
 
 var ErrFilterDoesNotExist = func(name string) error {
@@ -57,12 +57,11 @@ type HeaderRepository interface {
 	CreateOrUpdateHeader(header core.Header) (int64, error)
 	GetHeader(blockNumber int64) (core.Header, error)
 	MissingBlockNumbers(startingBlockNumber, endingBlockNumber int64, nodeID string) ([]int64, error)
-	HeaderExists(blockNumber int64) (bool, error)
 }
 
 type LogRepository interface {
 	CreateLogs(logs []core.Log, receiptId int64) error
-	GetLogs(address string, blockNumber int64) []core.Log
+	GetLogs(address string, blockNumber int64) ([]core.Log, error)
 }
 
 var ErrReceiptDoesNotExist = func(txHash string) error {

pkg/fakes/mock_block_repository.go

@@ -85,9 +85,10 @@ func (repository *MockBlockRepository) MissingBlockNumbers(startingBlockNumber i
 	return repository.missingBlockNumbersReturnArray
 }
 
-func (repository *MockBlockRepository) SetBlocksStatus(chainHead int64) {
+func (repository *MockBlockRepository) SetBlocksStatus(chainHead int64) error {
 	repository.setBlockStatusCalled = true
 	repository.setBlockStatusPassedChainHead = chainHead
+	return nil
 }
 
 func (repository *MockBlockRepository) AssertCreateOrUpdateBlockCallCountEquals(times int) {

pkg/fakes/mock_blockchain.go

@@ -108,8 +108,8 @@ func (chain *MockBlockChain) CallContract(contractHash string, input []byte, blo
 	return []byte{}, nil
 }
 
-func (chain *MockBlockChain) LastBlock() *big.Int {
+func (chain *MockBlockChain) LastBlock() (*big.Int, error) {
-	return chain.lastBlock
+	return chain.lastBlock, nil
 }
 
 func (chain *MockBlockChain) Node() core.Node {

pkg/fakes/mock_header_repository.go

@@ -65,14 +65,6 @@ func (repository *MockHeaderRepository) MissingBlockNumbers(startingBlockNumber,
 	return repository.missingBlockNumbers, nil
 }
 
-func (repository *MockHeaderRepository) HeaderExists(blockNumber int64) (bool, error) {
-	return repository.headerExists, nil
-}
-
-func (repository *MockHeaderRepository) SetHeaderExists(headerExists bool) {
-	repository.headerExists = headerExists
-}
-
 func (repository *MockHeaderRepository) SetGetHeaderError(err error) {
 	repository.getHeaderError = err
 }

pkg/geth/blockchain.go

@@ -81,7 +81,7 @@ func (blockChain *BlockChain) getPOWHeader(blockNumber int64) (header core.Heade
 	if err != nil {
 		return header, err
 	}
-	return blockChain.headerConverter.Convert(gethHeader, gethHeader.Hash().String())
+	return blockChain.headerConverter.Convert(gethHeader, gethHeader.Hash().String()), nil
 }
 
 func (blockChain *BlockChain) getPOWHeaders(blockNumbers []int64) (headers []core.Header, err error) {
@@ -113,8 +113,7 @@ func (blockChain *BlockChain) getPOWHeaders(blockNumbers []int64) (headers []cor
 
 	for _, POWHeader := range POWHeaders {
 		if POWHeader.Number != nil {
-			header, _ := blockChain.headerConverter.Convert(&POWHeader, POWHeader.Hash().String())
+			header := blockChain.headerConverter.Convert(&POWHeader, POWHeader.Hash().String())
-
 			headers = append(headers, header)
 		}
 	}
@@ -147,7 +146,7 @@ func (blockChain *BlockChain) getPOAHeader(blockNumber int64) (header core.Heade
 		GasUsed:     uint64(POAHeader.GasUsed),
 		Time:        POAHeader.Time.ToInt(),
 		Extra:       POAHeader.Extra,
-	}, POAHeader.Hash.String())
+	}, POAHeader.Hash.String()), nil
 }
 
 func (blockChain *BlockChain) getPOAHeaders(blockNumbers []int64) (headers []core.Header, err error) {
@@ -182,7 +181,7 @@ func (blockChain *BlockChain) getPOAHeaders(blockNumbers []int64) (headers []cor
 		var header core.Header
 		//Header.Number of the newest block will return nil.
 		if _, err := strconv.ParseUint(POAHeader.Number.ToInt().String(), 16, 64); err == nil {
-			header, _ = blockChain.headerConverter.Convert(&types.Header{
+			header = blockChain.headerConverter.Convert(&types.Header{
 				ParentHash:  POAHeader.ParentHash,
 				UncleHash:   POAHeader.UncleHash,
 				Coinbase:    POAHeader.Coinbase,
@@ -232,9 +231,9 @@ func (blockChain *BlockChain) GetEthLogsWithCustomQuery(query ethereum.FilterQue
 	return gethLogs, nil
 }
 
-func (blockChain *BlockChain) LastBlock() *big.Int {
+func (blockChain *BlockChain) LastBlock() (*big.Int, error) {
-	block, _ := blockChain.ethClient.HeaderByNumber(context.Background(), nil)
+	block, err := blockChain.ethClient.HeaderByNumber(context.Background(), nil)
-	return block.Number
+	return block.Number, err
 }
 
 func (blockChain *BlockChain) Node() core.Node {

pkg/geth/blockchain_test.go

@@ -221,7 +221,8 @@ var _ = Describe("Geth blockchain", func() {
 			blockNumber := int64(100)
 			mockClient.SetHeaderByNumberReturnHeader(&types.Header{Number: big.NewInt(blockNumber)})
 
-			result := blockChain.LastBlock()
+			result, err := blockChain.LastBlock()
+			Expect(err).NotTo(HaveOccurred())
 
 			mockClient.AssertHeaderByNumberCalledWith(context.Background(), nil)
 			Expect(result).To(Equal(big.NewInt(blockNumber)))

pkg/geth/cold_import/importer_test.go

@@ -20,7 +20,6 @@ import (
 	"github.com/ethereum/go-ethereum/core/types"
 	. "github.com/onsi/ginkgo"
 	. "github.com/onsi/gomega"
-
 	"github.com/vulcanize/vulcanizedb/pkg/datastore/postgres/repositories"
 	"github.com/vulcanize/vulcanizedb/pkg/fakes"
 	"github.com/vulcanize/vulcanizedb/pkg/geth/cold_import"
@@ -55,7 +54,8 @@ var _ = Describe("Geth cold importer", func() {
 		mockEthereumDatabase.SetReturnBlock(fakeGethBlock)
 		importer := cold_import.NewColdImporter(mockEthereumDatabase, mockBlockRepository, mockReceiptRepository, blockConverter)
 
-		importer.Execute(startingBlockNumber, endingBlockNumber, nodeId)
+		err := importer.Execute(startingBlockNumber, endingBlockNumber, nodeId)
+		Expect(err).NotTo(HaveOccurred())
 
 		mockBlockRepository.AssertMissingBlockNumbersCalledWith(startingBlockNumber, endingBlockNumber, nodeId)
 		mockEthereumDatabase.AssertGetBlockHashCalledWith(missingBlockNumber)
@@ -76,7 +76,8 @@ var _ = Describe("Geth cold importer", func() {
 		mockEthereumDatabase.SetReturnBlock(fakeGethBlock)
 		importer := cold_import.NewColdImporter(mockEthereumDatabase, mockBlockRepository, mockReceiptRepository, blockConverter)
 
-		importer.Execute(blockNumber, blockNumber, "node_id")
+		err := importer.Execute(blockNumber, blockNumber, "node_id")
+		Expect(err).NotTo(HaveOccurred())
 
 		mockEthereumDatabase.AssertGetBlockHashCalledWith(blockNumber)
 		mockEthereumDatabase.AssertGetBlockCalledWith(fakeHash, blockNumber)
@@ -101,8 +102,8 @@ var _ = Describe("Geth cold importer", func() {
 		mockEthereumDatabase.SetReturnBlock(fakeGethBlock)
 		importer := cold_import.NewColdImporter(mockEthereumDatabase, mockBlockRepository, mockReceiptRepository, blockConverter)
 
-		importer.Execute(startingBlockNumber, endingBlockNumber, "node_id")
+		err := importer.Execute(startingBlockNumber, endingBlockNumber, "node_id")
-
+		Expect(err).NotTo(HaveOccurred())
 		mockBlockRepository.AssertSetBlockStatusCalledWith(endingBlockNumber)
 	})
 
@@ -122,8 +123,8 @@ var _ = Describe("Geth cold importer", func() {
 		mockEthereumDatabase.SetReturnReceipts(fakeReceipts)
 		importer := cold_import.NewColdImporter(mockEthereumDatabase, mockBlockRepository, mockReceiptRepository, blockConverter)
 
-		importer.Execute(blockNumber, blockNumber, "node_id")
+		err := importer.Execute(blockNumber, blockNumber, "node_id")
-
+		Expect(err).NotTo(HaveOccurred())
 		expectedReceipts := vulcCommon.ToCoreReceipts(fakeReceipts)
 		mockReceiptRepository.AssertCreateReceiptsAndLogsCalledWith(blockId, expectedReceipts)
 	})

pkg/geth/converters/common/header_converter.go

@@ -25,7 +25,7 @@ import (
 
 type HeaderConverter struct{}
 
-func (converter HeaderConverter) Convert(gethHeader *types.Header, blockHash string) (core.Header, error) {
+func (converter HeaderConverter) Convert(gethHeader *types.Header, blockHash string) core.Header {
 	rawHeader, err := json.Marshal(gethHeader)
 	if err != nil {
 		panic(err)
@@ -36,5 +36,5 @@ func (converter HeaderConverter) Convert(gethHeader *types.Header, blockHash str
 		Raw:         rawHeader,
 		Timestamp:   gethHeader.Time.String(),
 	}
-	return coreHeader, nil
+	return coreHeader
 }

pkg/geth/converters/common/header_converter_test.go

@@ -44,9 +44,8 @@ var _ = Describe("Block header converter", func() {
 		converter := common2.HeaderConverter{}
 		hash := fakes.FakeHash.String()
 
-		coreHeader, err := converter.Convert(gethHeader, hash)
+		coreHeader := converter.Convert(gethHeader, hash)
 
-		Expect(err).NotTo(HaveOccurred())
 		Expect(coreHeader.BlockNumber).To(Equal(gethHeader.Number.Int64()))
 		Expect(coreHeader.Hash).To(Equal(hash))
 		Expect(coreHeader.Timestamp).To(Equal(gethHeader.Time.String()))
@@ -56,9 +55,8 @@ var _ = Describe("Block header converter", func() {
 		gethHeader := types.Header{Number: big.NewInt(123)}
 		converter := common2.HeaderConverter{}
 
-		coreHeader, err := converter.Convert(&gethHeader, fakes.FakeHash.String())
+		coreHeader := converter.Convert(&gethHeader, fakes.FakeHash.String())
 
-		Expect(err).NotTo(HaveOccurred())
 		expectedJSON, err := json.Marshal(gethHeader)
 		Expect(err).NotTo(HaveOccurred())
 		Expect(coreHeader.Raw).To(Equal(expectedJSON))

pkg/history/block_validator.go

@@ -17,6 +17,7 @@
 package history
 
 import (
+	"github.com/sirupsen/logrus"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore"
 )
@@ -35,11 +36,30 @@ func NewBlockValidator(blockchain core.BlockChain, blockRepository datastore.Blo
 	}
 }
 
-func (bv BlockValidator) ValidateBlocks() ValidationWindow {
+func (bv BlockValidator) ValidateBlocks() (ValidationWindow, error) {
-	window := MakeValidationWindow(bv.blockchain, bv.windowSize)
+	window, err := MakeValidationWindow(bv.blockchain, bv.windowSize)
+	if err != nil {
+		logrus.Error("ValidateBlocks: error creating validation window: ", err)
+		return ValidationWindow{}, err
+	}
+
 	blockNumbers := MakeRange(window.LowerBound, window.UpperBound)
-	RetrieveAndUpdateBlocks(bv.blockchain, bv.blockRepository, blockNumbers)
+	_, err = RetrieveAndUpdateBlocks(bv.blockchain, bv.blockRepository, blockNumbers)
-	lastBlock := bv.blockchain.LastBlock().Int64()
+	if err != nil {
-	bv.blockRepository.SetBlocksStatus(lastBlock)
+		logrus.Error("ValidateBlocks: error getting and updating blocks: ", err)
-	return window
+		return ValidationWindow{}, err
+	}
+
+	lastBlock, err := bv.blockchain.LastBlock()
+	if err != nil {
+		logrus.Error("ValidateBlocks: error getting last block: ", err)
+		return ValidationWindow{}, err
+	}
+
+	err = bv.blockRepository.SetBlocksStatus(lastBlock.Int64())
+	if err != nil {
+		logrus.Error("ValidateBlocks: error setting block status: ", err)
+		return ValidationWindow{}, err
+	}
+	return window, nil
 }

pkg/history/block_validator_test.go

@@ -34,7 +34,8 @@ var _ = Describe("Blocks validator", func() {
 		blocksRepository := fakes.NewMockBlockRepository()
 		validator := history.NewBlockValidator(blockChain, blocksRepository, 2)
 
-		window := validator.ValidateBlocks()
+		window, err := validator.ValidateBlocks()
+		Expect(err).NotTo(HaveOccurred())
 
 		Expect(window).To(Equal(history.ValidationWindow{LowerBound: 5, UpperBound: 7}))
 		blocksRepository.AssertCreateOrUpdateBlockCallCountEquals(3)
@@ -43,7 +44,7 @@ var _ = Describe("Blocks validator", func() {
 	It("returns the number of largest block", func() {
 		blockChain := fakes.NewMockBlockChain()
 		blockChain.SetLastBlock(big.NewInt(3))
-		maxBlockNumber := blockChain.LastBlock()
+		maxBlockNumber, _ := blockChain.LastBlock()
 
 		Expect(maxBlockNumber.Int64()).To(Equal(int64(3)))
 	})

pkg/history/header_validator.go

@@ -17,8 +17,7 @@
 package history
 
 import (
-	log "github.com/sirupsen/logrus"
+	"github.com/sirupsen/logrus"
-
 	"github.com/vulcanize/vulcanizedb/pkg/core"
 	"github.com/vulcanize/vulcanizedb/pkg/datastore"
 )
@@ -38,11 +37,15 @@ func NewHeaderValidator(blockChain core.BlockChain, repository datastore.HeaderR
 }
 
 func (validator HeaderValidator) ValidateHeaders() (ValidationWindow, error) {
-	window := MakeValidationWindow(validator.blockChain, validator.windowSize)
+	window, err := MakeValidationWindow(validator.blockChain, validator.windowSize)
-	blockNumbers := MakeRange(window.LowerBound, window.UpperBound)
-	_, err := RetrieveAndUpdateHeaders(validator.blockChain, validator.headerRepository, blockNumbers)
 	if err != nil {
-		log.Error("Error in ValidateHeaders: ", err)
+		logrus.Error("ValidateHeaders: error creating validation window: ", err)
+		return ValidationWindow{}, err
+	}
+	blockNumbers := MakeRange(window.LowerBound, window.UpperBound)
+	_, err = RetrieveAndUpdateHeaders(validator.blockChain, validator.headerRepository, blockNumbers)
+	if err != nil {
+		logrus.Error("ValidateHeaders: error getting/updating headers: ", err)
 		return ValidationWindow{}, err
 	}
 	return window, nil

pkg/history/populate_blocks.go

@@ -23,28 +23,41 @@ import (
 	"github.com/vulcanize/vulcanizedb/pkg/datastore"
 )
 
-func PopulateMissingBlocks(blockchain core.BlockChain, blockRepository datastore.BlockRepository, startingBlockNumber int64) int {
+func PopulateMissingBlocks(blockchain core.BlockChain, blockRepository datastore.BlockRepository, startingBlockNumber int64) (int, error) {
-	lastBlock := blockchain.LastBlock().Int64()
+	lastBlock, err := blockchain.LastBlock()
-	blockRange := blockRepository.MissingBlockNumbers(startingBlockNumber, lastBlock, blockchain.Node().ID)
+	if err != nil {
+		log.Error("PopulateMissingBlocks: error getting last block: ", err)
+		return 0, err
+	}
+	blockRange := blockRepository.MissingBlockNumbers(startingBlockNumber, lastBlock.Int64(), blockchain.Node().ID)
 
 	if len(blockRange) == 0 {
-		return 0
+		return 0, nil
 	}
 
 	log.Printf("Backfilling %d blocks\n\n", len(blockRange))
-	RetrieveAndUpdateBlocks(blockchain, blockRepository, blockRange)
+	_, err = RetrieveAndUpdateBlocks(blockchain, blockRepository, blockRange)
-	return len(blockRange)
+	if err != nil {
+		log.Error("PopulateMissingBlocks: error gettings/updating blocks: ", err)
+		return 0, err
+	}
+	return len(blockRange), nil
 }
 
-func RetrieveAndUpdateBlocks(blockchain core.BlockChain, blockRepository datastore.BlockRepository, blockNumbers []int64) int {
+func RetrieveAndUpdateBlocks(blockchain core.BlockChain, blockRepository datastore.BlockRepository, blockNumbers []int64) (int, error) {
 	for _, blockNumber := range blockNumbers {
 		block, err := blockchain.GetBlockByNumber(blockNumber)
 		if err != nil {
-			log.Printf("failed to retrieve block number: %d\n", blockNumber)
+			log.Error("RetrieveAndUpdateBlocks: error getting block: ", err)
-			return 0
+			return 0, err
 		}
-		// TODO: handle possible error here
+
-		blockRepository.CreateOrUpdateBlock(block)
+		_, err = blockRepository.CreateOrUpdateBlock(block)
+		if err != nil {
+			log.Error("RetrieveAndUpdateBlocks: error creating/updating block: ", err)
+			return 0, err
+		}
+
 	}
-	return len(blockNumbers)
+	return len(blockNumbers), nil
 }

pkg/history/populate_blocks_test.go

@@ -36,8 +36,9 @@ var _ = Describe("Populating blocks", func() {
 		blockChain.SetLastBlock(big.NewInt(2))
 		blockRepository.SetMissingBlockNumbersReturnArray([]int64{2})
 
-		blocksAdded := history.PopulateMissingBlocks(blockChain, blockRepository, 1)
+		blocksAdded, err := history.PopulateMissingBlocks(blockChain, blockRepository, 1)
-		_, err := blockRepository.GetBlock(1)
+		Expect(err).NotTo(HaveOccurred())
+		_, err = blockRepository.GetBlock(1)
 
 		Expect(blocksAdded).To(Equal(1))
 		Expect(err).ToNot(HaveOccurred())
@@ -48,8 +49,9 @@ var _ = Describe("Populating blocks", func() {
 		blockChain.SetLastBlock(big.NewInt(13))
 		blockRepository.SetMissingBlockNumbersReturnArray([]int64{5, 8, 10})
 
-		blocksAdded := history.PopulateMissingBlocks(blockChain, blockRepository, 5)
+		blocksAdded, err := history.PopulateMissingBlocks(blockChain, blockRepository, 5)
 
+		Expect(err).NotTo(HaveOccurred())
 		Expect(blocksAdded).To(Equal(3))
 		blockRepository.AssertCreateOrUpdateBlocksCallCountAndBlockNumbersEquals(3, []int64{5, 8, 10})
 	})
@@ -59,16 +61,18 @@ var _ = Describe("Populating blocks", func() {
 		blockChain.SetLastBlock(big.NewInt(6))
 		blockRepository.SetMissingBlockNumbersReturnArray([]int64{4, 5})
 
-		numberOfBlocksCreated := history.PopulateMissingBlocks(blockChain, blockRepository, 3)
+		numberOfBlocksCreated, err := history.PopulateMissingBlocks(blockChain, blockRepository, 3)
 
+		Expect(err).NotTo(HaveOccurred())
 		Expect(numberOfBlocksCreated).To(Equal(2))
 	})
 
 	It("updates the repository with a range of blocks w/in the range ", func() {
 		blockChain := fakes.NewMockBlockChain()
 
-		history.RetrieveAndUpdateBlocks(blockChain, blockRepository, history.MakeRange(2, 5))
+		_, err := history.RetrieveAndUpdateBlocks(blockChain, blockRepository, history.MakeRange(2, 5))
 
+		Expect(err).NotTo(HaveOccurred())
 		blockRepository.AssertCreateOrUpdateBlocksCallCountAndBlockNumbersEquals(4, []int64{2, 3, 4, 5})
 	})
 
@@ -77,8 +81,9 @@ var _ = Describe("Populating blocks", func() {
 		blockChain.SetGetBlockByNumberErr(fakes.FakeError)
 		blocks := history.MakeRange(1, 10)
 
-		history.RetrieveAndUpdateBlocks(blockChain, blockRepository, blocks)
+		_, err := history.RetrieveAndUpdateBlocks(blockChain, blockRepository, blocks)
 
+		Expect(err).To(HaveOccurred())
 		blockRepository.AssertCreateOrUpdateBlockCallCountEquals(0)
 	})
 })

pkg/history/populate_headers.go

@@ -25,25 +25,24 @@ import (
 )
 
 func PopulateMissingHeaders(blockchain core.BlockChain, headerRepository datastore.HeaderRepository, startingBlockNumber int64) (int, error) {
-	lastBlock := blockchain.LastBlock().Int64()
+	lastBlock, err := blockchain.LastBlock()
-	headerAlreadyExists, err := headerRepository.HeaderExists(lastBlock)
-
 	if err != nil {
-		log.Error("Error in checking header in PopulateMissingHeaders: ", err)
+		log.Error("PopulateMissingHeaders: Error getting last block: ", err)
 		return 0, err
-	} else if headerAlreadyExists {
-		return 0, nil
 	}
 
-	blockNumbers, err := headerRepository.MissingBlockNumbers(startingBlockNumber, lastBlock, blockchain.Node().ID)
+	blockNumbers, err := headerRepository.MissingBlockNumbers(startingBlockNumber, lastBlock.Int64(), blockchain.Node().ID)
 	if err != nil {
-		log.Error("Error getting missing block numbers in PopulateMissingHeaders: ", err)
+		log.Error("PopulateMissingHeaders: Error getting missing block numbers: ", err)
 		return 0, err
+	} else if len(blockNumbers) == 0 {
+		return 0, nil
 	}
 
 	log.Printf("Backfilling %d blocks\n\n", len(blockNumbers))
 	_, err = RetrieveAndUpdateHeaders(blockchain, headerRepository, blockNumbers)
 	if err != nil {
+		log.Error("PopulateMissingHeaders: Error getting/updating headers:", err)
 		return 0, err
 	}
 	return len(blockNumbers), nil

pkg/history/populate_headers_test.go

@@ -59,7 +59,6 @@ var _ = Describe("Populating headers", func() {
 	It("returns early if the db is already synced up to the head of the chain", func() {
 		blockChain := fakes.NewMockBlockChain()
 		blockChain.SetLastBlock(big.NewInt(2))
-		headerRepository.SetHeaderExists(true)
 		headersAdded, err := history.PopulateMissingHeaders(blockChain, headerRepository, 2)
 
 		Expect(err).NotTo(HaveOccurred())

pkg/history/validation_window.go

@@ -18,17 +18,10 @@ package history
 
 import (
 	"fmt"
+	log "github.com/sirupsen/logrus"
 	"github.com/vulcanize/vulcanizedb/pkg/core"
-	"text/template"
 )
 
-const WindowTemplate = `Validating Blocks
-|{{.LowerBound}}|-- Validation Window --|{{.UpperBound}}| ({{.UpperBound}}:HEAD)
-
-`
-
-var ParsedWindowTemplate = *template.Must(template.New("window").Parse(WindowTemplate))
-
 type ValidationWindow struct {
 	LowerBound int64
 	UpperBound int64
@@ -38,10 +31,14 @@ func (window ValidationWindow) Size() int {
 	return int(window.UpperBound - window.LowerBound)
 }
 
-func MakeValidationWindow(blockchain core.BlockChain, windowSize int) ValidationWindow {
+func MakeValidationWindow(blockchain core.BlockChain, windowSize int) (ValidationWindow, error) {
-	upperBound := blockchain.LastBlock().Int64()
+	upperBound, err := blockchain.LastBlock()
-	lowerBound := upperBound - int64(windowSize)
+	if err != nil {
-	return ValidationWindow{lowerBound, upperBound}
+		log.Error("MakeValidationWindow: error getting LastBlock: ", err)
+		return ValidationWindow{}, err
+	}
+	lowerBound := upperBound.Int64() - int64(windowSize)
+	return ValidationWindow{lowerBound, upperBound.Int64()}, nil
 }
 
 func MakeRange(min, max int64) []int64 {

pkg/history/validation_window_test.go

@@ -30,8 +30,9 @@ var _ = Describe("Validation window", func() {
 		blockChain := fakes.NewMockBlockChain()
 		blockChain.SetLastBlock(big.NewInt(5))
 
-		validationWindow := history.MakeValidationWindow(blockChain, 2)
+		validationWindow, err := history.MakeValidationWindow(blockChain, 2)
 
+		Expect(err).NotTo(HaveOccurred())
 		Expect(validationWindow.LowerBound).To(Equal(int64(3)))
 		Expect(validationWindow.UpperBound).To(Equal(int64(5)))
 	})