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backend.go
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backend.go
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package backend
import (
"context"
"crypto/md5" //nolint:gosec
"errors"
"fmt"
"sync"
"time"
accessproto "github.com/onflow/flow/protobuf/go/flow/access"
"github.com/rs/zerolog"
"google.golang.org/grpc/codes"
"google.golang.org/grpc/status"
"github.com/onflow/flow-go/access"
"github.com/onflow/flow-go/engine/common/rpc/convert"
"github.com/onflow/flow-go/model/flow"
"github.com/onflow/flow-go/model/flow/filter"
"github.com/onflow/flow-go/module"
"github.com/onflow/flow-go/state/protocol"
"github.com/onflow/flow-go/storage"
)
// maxExecutionNodesCnt is the max number of execution nodes that will be contacted to complete an execution api request
const maxExecutionNodesCnt = 3
// minExecutionNodesCnt is the minimum number of execution nodes expected to have sent the execution receipt for a block
const minExecutionNodesCnt = 2
// maxAttemptsForExecutionReceipt is the maximum number of attempts to find execution receipts for a given block ID
const maxAttemptsForExecutionReceipt = 3
// DefaultMaxHeightRange is the default maximum size of range requests.
const DefaultMaxHeightRange = 250
// DefaultSnapshotHistoryLimit the amount of blocks to look back in state
// when recursively searching for a valid snapshot
const DefaultSnapshotHistoryLimit = 50
// DefaultConnectionPoolSize is the default size for the connection pool to collection and execution nodes
const DefaultConnectionPoolSize = 50
var preferredENIdentifiers flow.IdentifierList
var fixedENIdentifiers flow.IdentifierList
var SnapshotHistoryLimitErr = fmt.Errorf("reached the snapshot history limit")
// Backend implements the Access API.
//
// It is composed of several sub-backends that implement part of the Access API.
//
// Script related calls are handled by backendScripts.
// Transaction related calls are handled by backendTransactions.
// Block Header related calls are handled by backendBlockHeaders.
// Block details related calls are handled by backendBlockDetails.
// Event related calls are handled by backendEvents.
// Account related calls are handled by backendAccounts.
//
// All remaining calls are handled by the base Backend in this file.
type Backend struct {
backendScripts
backendTransactions
backendEvents
backendBlockHeaders
backendBlockDetails
backendAccounts
backendExecutionResults
state protocol.State
chainID flow.ChainID
collections storage.Collections
executionReceipts storage.ExecutionReceipts
connFactory ConnectionFactory
snapshotHistoryLimit int
}
func New(
state protocol.State,
collectionRPC accessproto.AccessAPIClient,
historicalAccessNodes []accessproto.AccessAPIClient,
blocks storage.Blocks,
headers storage.Headers,
collections storage.Collections,
transactions storage.Transactions,
executionReceipts storage.ExecutionReceipts,
executionResults storage.ExecutionResults,
chainID flow.ChainID,
transactionMetrics module.TransactionMetrics,
connFactory ConnectionFactory,
retryEnabled bool,
maxHeightRange uint,
preferredExecutionNodeIDs []string,
fixedExecutionNodeIDs []string,
log zerolog.Logger,
snapshotHistoryLimit int,
) *Backend {
retry := newRetry()
if retryEnabled {
retry.Activate()
}
b := &Backend{
state: state,
// create the sub-backends
backendScripts: backendScripts{
headers: headers,
executionReceipts: executionReceipts,
connFactory: connFactory,
state: state,
log: log,
metrics: transactionMetrics,
seenScripts: &scriptMap{
scripts: make(map[[md5.Size]byte]time.Time),
lock: sync.RWMutex{},
},
},
backendTransactions: backendTransactions{
staticCollectionRPC: collectionRPC,
state: state,
chainID: chainID,
collections: collections,
blocks: blocks,
transactions: transactions,
executionReceipts: executionReceipts,
transactionValidator: configureTransactionValidator(state, chainID),
transactionMetrics: transactionMetrics,
retry: retry,
connFactory: connFactory,
previousAccessNodes: historicalAccessNodes,
log: log,
},
backendEvents: backendEvents{
state: state,
headers: headers,
executionReceipts: executionReceipts,
connFactory: connFactory,
log: log,
maxHeightRange: maxHeightRange,
},
backendBlockHeaders: backendBlockHeaders{
headers: headers,
state: state,
},
backendBlockDetails: backendBlockDetails{
blocks: blocks,
state: state,
},
backendAccounts: backendAccounts{
state: state,
headers: headers,
executionReceipts: executionReceipts,
connFactory: connFactory,
log: log,
},
backendExecutionResults: backendExecutionResults{
executionResults: executionResults,
},
collections: collections,
executionReceipts: executionReceipts,
connFactory: connFactory,
chainID: chainID,
snapshotHistoryLimit: snapshotHistoryLimit,
}
retry.SetBackend(b)
var err error
preferredENIdentifiers, err = identifierList(preferredExecutionNodeIDs)
if err != nil {
log.Fatal().Err(err).Msg("failed to convert node id string to Flow Identifier for preferred EN map")
}
fixedENIdentifiers, err = identifierList(fixedExecutionNodeIDs)
if err != nil {
log.Fatal().Err(err).Msg("failed to convert node id string to Flow Identifier for fixed EN map")
}
return b
}
func identifierList(ids []string) (flow.IdentifierList, error) {
idList := make(flow.IdentifierList, len(ids))
for i, idStr := range ids {
id, err := flow.HexStringToIdentifier(idStr)
if err != nil {
return nil, fmt.Errorf("failed to convert node id string %s to Flow Identifier: %v", id, err)
}
idList[i] = id
}
return idList, nil
}
func configureTransactionValidator(state protocol.State, chainID flow.ChainID) *access.TransactionValidator {
return access.NewTransactionValidator(
access.NewProtocolStateBlocks(state),
chainID.Chain(),
access.TransactionValidationOptions{
Expiry: flow.DefaultTransactionExpiry,
ExpiryBuffer: flow.DefaultTransactionExpiryBuffer,
AllowEmptyReferenceBlockID: false,
AllowUnknownReferenceBlockID: false,
CheckScriptsParse: false,
MaxGasLimit: flow.DefaultMaxTransactionGasLimit,
MaxTransactionByteSize: flow.DefaultMaxTransactionByteSize,
MaxCollectionByteSize: flow.DefaultMaxCollectionByteSize,
},
)
}
// Ping responds to requests when the server is up.
func (b *Backend) Ping(ctx context.Context) error {
// staticCollectionRPC is only set if a collection node address was provided at startup
if b.staticCollectionRPC != nil {
_, err := b.staticCollectionRPC.Ping(ctx, &accessproto.PingRequest{})
if err != nil {
return fmt.Errorf("could not ping collection node: %w", err)
}
}
return nil
}
func (b *Backend) GetCollectionByID(_ context.Context, colID flow.Identifier) (*flow.LightCollection, error) {
// retrieve the collection from the collection storage
col, err := b.collections.LightByID(colID)
if err != nil {
// Collections are retrieved asynchronously as we finalize blocks, so
// it is possible for a client to request a finalized block from us
// containing some collection, then get a not found error when requesting
// that collection. These clients should retry.
err = convertStorageError(fmt.Errorf("please retry for collection in finalized block: %w", err))
return nil, err
}
return col, nil
}
func (b *Backend) GetNetworkParameters(_ context.Context) access.NetworkParameters {
return access.NetworkParameters{
ChainID: b.chainID,
}
}
// GetLatestProtocolStateSnapshot returns the latest finalized snapshot
func (b *Backend) GetLatestProtocolStateSnapshot(_ context.Context) ([]byte, error) {
snapshot := b.state.Final()
validSnapshot, err := b.getValidSnapshot(snapshot, 0)
if err != nil {
return nil, err
}
return convert.SnapshotToBytes(validSnapshot)
}
// getValidSnapshot will return a valid snapshot that has a sealing segment which
// 1. does not contain any blocks that span an epoch transition
// 2. does not contain any blocks that span an epoch phase transition
// If a snapshot does contain an invalid sealing segment query the state
// by height of each block in the segment and return a snapshot at the point
// where the transition happens.
func (b *Backend) getValidSnapshot(snapshot protocol.Snapshot, blocksVisited int) (protocol.Snapshot, error) {
segment, err := snapshot.SealingSegment()
if err != nil {
return nil, fmt.Errorf("failed to get sealing segment: %w", err)
}
counterAtHighest, phaseAtHighest, err := b.getCounterAndPhase(segment.Highest().Header.Height)
if err != nil {
return nil, fmt.Errorf("failed to get counter and phase at highest block in the segment: %w", err)
}
counterAtLowest, phaseAtLowest, err := b.getCounterAndPhase(segment.Lowest().Header.Height)
if err != nil {
return nil, fmt.Errorf("failed to get counter and phase at lowest block in the segment: %w", err)
}
// Check if the counters and phase are different this indicates that the sealing segment
// of the snapshot requested spans either an epoch transition or phase transition.
if b.isEpochOrPhaseDifferent(counterAtHighest, counterAtLowest, phaseAtHighest, phaseAtLowest) {
// Visit each node in strict order of decreasing height starting at head
// to find the block that straddles the transition boundary.
for i := len(segment.Blocks) - 1; i >= 0; i-- {
blocksVisited++
// NOTE: Check if we have reached our history limit, in edge cases
// where the sealing segment is abnormally long we want to short circuit
// the recursive calls and return an error. The API caller can retry.
if blocksVisited > b.snapshotHistoryLimit {
return nil, fmt.Errorf("%w: (%d)", SnapshotHistoryLimitErr, b.snapshotHistoryLimit)
}
counterAtBlock, phaseAtBlock, err := b.getCounterAndPhase(segment.Blocks[i].Header.Height)
if err != nil {
return nil, fmt.Errorf("failed to get epoch counter and phase for snapshot at block %s: %w", segment.Blocks[i].ID(), err)
}
// Check if this block straddles the transition boundary, if it does return the snapshot
// at that block height.
if b.isEpochOrPhaseDifferent(counterAtHighest, counterAtBlock, phaseAtHighest, phaseAtBlock) {
return b.getValidSnapshot(b.state.AtHeight(segment.Blocks[i].Header.Height), blocksVisited)
}
}
}
return snapshot, nil
}
// getCounterAndPhase will return the epoch counter and phase at the specified height in state
func (b *Backend) getCounterAndPhase(height uint64) (uint64, flow.EpochPhase, error) {
snapshot := b.state.AtHeight(height)
counter, err := snapshot.Epochs().Current().Counter()
if err != nil {
return 0, 0, fmt.Errorf("failed to get counter for block (height=%d): %w", height, err)
}
phase, err := snapshot.Phase()
if err != nil {
return 0, 0, fmt.Errorf("failed to get phase for block (height=%d): %w", height, err)
}
return counter, phase, nil
}
func (b *Backend) isEpochOrPhaseDifferent(counter1, counter2 uint64, phase1, phase2 flow.EpochPhase) bool {
return counter1 != counter2 || phase1 != phase2
}
func convertStorageError(err error) error {
if err == nil {
return nil
}
if status.Code(err) == codes.NotFound {
// Already converted
return err
}
if errors.Is(err, storage.ErrNotFound) {
return status.Errorf(codes.NotFound, "not found: %v", err)
}
return status.Errorf(codes.Internal, "failed to find: %v", err)
}
// executionNodesForBlockID returns upto maxExecutionNodesCnt number of randomly chosen execution node identities
// which have executed the given block ID.
// If no such execution node is found, an InsufficientExecutionReceipts error is returned.
func executionNodesForBlockID(
ctx context.Context,
blockID flow.Identifier,
executionReceipts storage.ExecutionReceipts,
state protocol.State,
log zerolog.Logger) (flow.IdentityList, error) {
var executorIDs flow.IdentifierList
// check if the block ID is of the root block. If it is then don't look for execution receipts since they
// will not be present for the root block.
rootBlock, err := state.Params().Root()
if err != nil {
return nil, fmt.Errorf("failed to retreive execution IDs for block ID %v: %w", blockID, err)
}
if rootBlock.ID() == blockID {
executorIdentities, err := state.Final().Identities(filter.HasRole(flow.RoleExecution))
if err != nil {
return nil, fmt.Errorf("failed to retreive execution IDs for block ID %v: %w", blockID, err)
}
executorIDs = executorIdentities.NodeIDs()
} else {
// try to find atleast minExecutionNodesCnt execution node ids from the execution receipts for the given blockID
for attempt := 0; attempt < maxAttemptsForExecutionReceipt; attempt++ {
executorIDs, err = findAllExecutionNodes(blockID, executionReceipts, log)
if err != nil {
return nil, err
}
if len(executorIDs) >= minExecutionNodesCnt {
break
}
// log the attempt
log.Debug().Int("attempt", attempt).Int("max_attempt", maxAttemptsForExecutionReceipt).
Int("execution_receipts_found", len(executorIDs)).
Str("block_id", blockID.String()).
Msg("insufficient execution receipts")
// if one or less execution receipts may have been received then re-query
// in the hope that more might have been received by now
select {
case <-ctx.Done():
return nil, ctx.Err()
case <-time.After(100 * time.Millisecond << time.Duration(attempt)):
//retry after an exponential backoff
}
}
receiptCnt := len(executorIDs)
// if less than minExecutionNodesCnt execution receipts have been received so far, then return random ENs
if receiptCnt < minExecutionNodesCnt {
newExecutorIDs, err := state.AtBlockID(blockID).Identities(filter.HasRole(flow.RoleExecution))
if err != nil {
return nil, fmt.Errorf("failed to retreive execution IDs for block ID %v: %w", blockID, err)
}
executorIDs = newExecutorIDs.NodeIDs()
}
}
// choose from the preferred or fixed execution nodes
subsetENs, err := chooseExecutionNodes(state, executorIDs)
if err != nil {
return nil, fmt.Errorf("failed to retreive execution IDs for block ID %v: %w", blockID, err)
}
// randomly choose upto maxExecutionNodesCnt identities
executionIdentitiesRandom := subsetENs.Sample(maxExecutionNodesCnt)
if len(executionIdentitiesRandom) == 0 {
return nil, fmt.Errorf("no matching execution node found for block ID %v", blockID)
}
return executionIdentitiesRandom, nil
}
// findAllExecutionNodes find all the execution nodes ids from the execution receipts that have been received for the
// given blockID
func findAllExecutionNodes(
blockID flow.Identifier,
executionReceipts storage.ExecutionReceipts,
log zerolog.Logger) (flow.IdentifierList, error) {
// lookup the receipt's storage with the block ID
allReceipts, err := executionReceipts.ByBlockID(blockID)
if err != nil {
return nil, fmt.Errorf("failed to retreive execution receipts for block ID %v: %w", blockID, err)
}
executionResultMetaList := make(flow.ExecutionReceiptMetaList, 0, len(allReceipts))
for _, r := range allReceipts {
executionResultMetaList = append(executionResultMetaList, r.Meta())
}
executionResultGroupedMetaList := executionResultMetaList.GroupByResultID()
// maximum number of matching receipts found so far for any execution result id
maxMatchedReceiptCnt := 0
// execution result id key for the highest number of matching receipts in the identicalReceipts map
var maxMatchedReceiptResultID flow.Identifier
// find the largest list of receipts which have the same result ID
for resultID, executionReceiptList := range executionResultGroupedMetaList {
currentMatchedReceiptCnt := executionReceiptList.Size()
if currentMatchedReceiptCnt > maxMatchedReceiptCnt {
maxMatchedReceiptCnt = currentMatchedReceiptCnt
maxMatchedReceiptResultID = resultID
}
}
// if there are more than one execution result for the same block ID, log as error
if executionResultGroupedMetaList.NumberGroups() > 1 {
identicalReceiptsStr := fmt.Sprintf("%v", flow.GetIDs(allReceipts))
log.Error().
Str("block_id", blockID.String()).
Str("execution_receipts", identicalReceiptsStr).
Msg("execution receipt mismatch")
}
// pick the largest list of matching receipts
matchingReceiptMetaList := executionResultGroupedMetaList.GetGroup(maxMatchedReceiptResultID)
metaReceiptGroupedByExecutorID := matchingReceiptMetaList.GroupByExecutorID()
// collect all unique execution node ids from the receipts
var executorIDs flow.IdentifierList
for executorID := range metaReceiptGroupedByExecutorID {
executorIDs = append(executorIDs, executorID)
}
return executorIDs, nil
}
// chooseExecutionNodes finds the subset of execution nodes defined in the identity table by first
// choosing the preferred execution nodes which have executed the transaction. If no such preferred
// execution nodes are found, then the fixed execution nodes defined in the identity table are returned
// If neither preferred nor fixed nodes are defined, then all execution node matching the executor IDs are returned.
// e.g. If execution nodes in identity table are {1,2,3,4}, preferred ENs are defined as {2,3,4}
// and the executor IDs is {1,2,3}, then {2, 3} is returned as the chosen subset of ENs
func chooseExecutionNodes(state protocol.State, executorIDs flow.IdentifierList) (flow.IdentityList, error) {
allENs, err := state.Final().Identities(filter.HasRole(flow.RoleExecution))
if err != nil {
return nil, fmt.Errorf("failed to retreive all execution IDs: %w", err)
}
// first try and choose from the preferred EN IDs
var chosenIDs flow.IdentityList
if len(preferredENIdentifiers) > 0 {
// find the preferred execution node IDs which have executed the transaction
chosenIDs = allENs.Filter(filter.And(filter.HasNodeID(preferredENIdentifiers...),
filter.HasNodeID(executorIDs...)))
if len(chosenIDs) > 0 {
return chosenIDs, nil
}
}
// if no preferred EN ID is found, then choose from the fixed EN IDs
if len(fixedENIdentifiers) > 0 {
// choose fixed ENs which have executed the transaction
chosenIDs = allENs.Filter(filter.And(filter.HasNodeID(fixedENIdentifiers...), filter.HasNodeID(executorIDs...)))
if len(chosenIDs) > 0 {
return chosenIDs, nil
}
// if no such ENs are found then just choose all fixed ENs
chosenIDs = allENs.Filter(filter.HasNodeID(fixedENIdentifiers...))
return chosenIDs, nil
}
// If no preferred or fixed ENs have been specified, then return all executor IDs i.e. no preference at all
return allENs.Filter(filter.HasNodeID(executorIDs...)), nil
}