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replica_raftstorage.go
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replica_raftstorage.go
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// Copyright 2015 The Cockroach Authors.
//
// 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.
package storage
import (
"fmt"
"time"
"github.com/coreos/etcd/raft"
"github.com/coreos/etcd/raft/raftpb"
"github.com/pkg/errors"
"golang.org/x/net/context"
"github.com/cockroachdb/cockroach/pkg/keys"
"github.com/cockroachdb/cockroach/pkg/roachpb"
"github.com/cockroachdb/cockroach/pkg/storage/engine"
"github.com/cockroachdb/cockroach/pkg/storage/engine/enginepb"
"github.com/cockroachdb/cockroach/pkg/storage/storagebase"
"github.com/cockroachdb/cockroach/pkg/util/hlc"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/timeutil"
"github.com/cockroachdb/cockroach/pkg/util/uuid"
)
// replicaRaftStorage implements the raft.Storage interface.
type replicaRaftStorage Replica
var _ raft.Storage = (*replicaRaftStorage)(nil)
// All calls to raft.RawNode require that both Replica.raftMu and
// Replica.mu are held. All of the functions exposed via the
// raft.Storage interface will in turn be called from RawNode, so none
// of these methods may acquire either lock, but they may require
// their caller to hold one or both locks (even though they do not
// follow our "Locked" naming convention). Specific locking
// requirements are noted in each method's comments.
//
// Many of the methods defined in this file are wrappers around static
// functions. This is done to facilitate their use from
// Replica.Snapshot(), where it is important that all the data that
// goes into the snapshot comes from a consistent view of the
// database, and not the replica's in-memory state or via a reference
// to Replica.store.Engine().
// InitialState implements the raft.Storage interface.
// InitialState requires that r.mu is held.
func (r *replicaRaftStorage) InitialState() (raftpb.HardState, raftpb.ConfState, error) {
ctx := r.AnnotateCtx(context.TODO())
hs, err := r.mu.stateLoader.loadHardState(ctx, r.store.Engine())
// For uninitialized ranges, membership is unknown at this point.
if raft.IsEmptyHardState(hs) || err != nil {
return raftpb.HardState{}, raftpb.ConfState{}, err
}
var cs raftpb.ConfState
for _, rep := range r.mu.state.Desc.Replicas {
cs.Nodes = append(cs.Nodes, uint64(rep.ReplicaID))
}
return hs, cs, nil
}
// Entries implements the raft.Storage interface. Note that maxBytes is advisory
// and this method will always return at least one entry even if it exceeds
// maxBytes. Passing maxBytes equal to zero disables size checking. Sideloaded
// proposals count towards maxBytes with their payloads inlined.
func (r *replicaRaftStorage) Entries(lo, hi, maxBytes uint64) ([]raftpb.Entry, error) {
readonly := r.store.Engine().NewReadOnly()
defer readonly.Close()
ctx := r.AnnotateCtx(context.TODO())
return entries(ctx, readonly, r.RangeID, r.store.raftEntryCache,
r.raftMu.sideloaded, lo, hi, maxBytes)
}
// raftEntriesLocked requires that r.mu is held.
func (r *Replica) raftEntriesLocked(lo, hi, maxBytes uint64) ([]raftpb.Entry, error) {
return (*replicaRaftStorage)(r).Entries(lo, hi, maxBytes)
}
// entries retrieves entries from the engine. To accommodate loading the term,
// `sideloaded` can be supplied as nil, in which case sideloaded entries will
// not be inlined, the raft entry cache will not be populated with *any* of the
// loaded entries, and maxBytes will not be applied to the payloads.
func entries(
ctx context.Context,
e engine.Reader,
rangeID roachpb.RangeID,
eCache *raftEntryCache,
sideloaded sideloadStorage,
lo, hi, maxBytes uint64,
) ([]raftpb.Entry, error) {
if lo > hi {
return nil, errors.Errorf("lo:%d is greater than hi:%d", lo, hi)
}
n := hi - lo
if n > 100 {
n = 100
}
ents := make([]raftpb.Entry, 0, n)
ents, size, hitIndex := eCache.getEntries(ents, rangeID, lo, hi, maxBytes)
// Return results if the correct number of results came back or if
// we ran into the max bytes limit.
if uint64(len(ents)) == hi-lo || (maxBytes > 0 && size > maxBytes) {
return ents, nil
}
// Scan over the log to find the requested entries in the range [lo, hi),
// stopping once we have enough.
expectedIndex := hitIndex
// Whether we can populate the Raft entries cache. False if we found a
// sideloaded proposal, but the caller didn't give us a sideloaded storage.
canCache := true
var ent raftpb.Entry
exceededMaxBytes := false
scanFunc := func(kv roachpb.KeyValue) (bool, error) {
if err := kv.Value.GetProto(&ent); err != nil {
return false, err
}
// Exit early if we have any gaps or it has been compacted.
if ent.Index != expectedIndex {
return true, nil
}
expectedIndex++
if sniffSideloadedRaftCommand(ent.Data) {
canCache = canCache && sideloaded != nil
if sideloaded != nil {
newEnt, err := maybeInlineSideloadedRaftCommand(
ctx, rangeID, ent, sideloaded, eCache,
)
if err != nil {
return true, err
}
if newEnt != nil {
ent = *newEnt
}
}
}
// Note that we track the size of proposals with payloads inlined.
size += uint64(ent.Size())
ents = append(ents, ent)
exceededMaxBytes = maxBytes > 0 && size > maxBytes
return exceededMaxBytes, nil
}
if err := iterateEntries(ctx, e, rangeID, expectedIndex, hi, scanFunc); err != nil {
return nil, err
}
// Cache the fetched entries, if we may.
if canCache {
eCache.addEntries(rangeID, ents)
}
// Did the correct number of results come back? If so, we're all good.
if uint64(len(ents)) == hi-lo {
return ents, nil
}
// Did we hit the size limit? If so, return what we have.
if exceededMaxBytes {
return ents, nil
}
// Did we get any results at all? Because something went wrong.
if len(ents) > 0 {
// Was the lo already truncated?
if ents[0].Index > lo {
return nil, raft.ErrCompacted
}
// Was the missing index after the last index?
lastIndex, err := loadLastIndex(ctx, e, rangeID)
if err != nil {
return nil, err
}
if lastIndex <= expectedIndex {
return nil, raft.ErrUnavailable
}
// We have a gap in the record, if so, return a nasty error.
return nil, errors.Errorf("there is a gap in the index record between lo:%d and hi:%d at index:%d", lo, hi, expectedIndex)
}
// No results, was it due to unavailability or truncation?
ts, err := loadTruncatedState(ctx, e, rangeID)
if err != nil {
return nil, err
}
if ts.Index >= lo {
// The requested lo index has already been truncated.
return nil, raft.ErrCompacted
}
// The requested lo index does not yet exist.
return nil, raft.ErrUnavailable
}
func iterateEntries(
ctx context.Context,
e engine.Reader,
rangeID roachpb.RangeID,
lo,
hi uint64,
scanFunc func(roachpb.KeyValue) (bool, error),
) error {
_, err := engine.MVCCIterate(
ctx, e,
keys.RaftLogKey(rangeID, lo),
keys.RaftLogKey(rangeID, hi),
hlc.Timestamp{},
true, /* consistent */
nil, /* txn */
false, /* !reverse */
scanFunc,
)
return err
}
// invalidLastTerm is an out-of-band value for r.mu.lastTerm that
// invalidates lastTerm caching and forces retrieval of Term(lastTerm)
// from the raftEntryCache/RocksDB.
const invalidLastTerm = 0
// Term implements the raft.Storage interface.
func (r *replicaRaftStorage) Term(i uint64) (uint64, error) {
// TODO(nvanbenschoten): should we set r.mu.lastTerm when
// r.mu.lastIndex == i && r.mu.lastTerm == invalidLastTerm?
if r.mu.lastIndex == i && r.mu.lastTerm != invalidLastTerm {
return r.mu.lastTerm, nil
}
// Try to retrieve the term for the desired entry from the entry cache.
if term, ok := r.store.raftEntryCache.getTerm(r.RangeID, i); ok {
return term, nil
}
readonly := r.store.Engine().NewReadOnly()
defer readonly.Close()
ctx := r.AnnotateCtx(context.TODO())
return term(ctx, readonly, r.RangeID, r.store.raftEntryCache, i)
}
// raftTermLocked requires that r.mu is locked for reading.
func (r *Replica) raftTermRLocked(i uint64) (uint64, error) {
return (*replicaRaftStorage)(r).Term(i)
}
func term(
ctx context.Context, eng engine.Reader, rangeID roachpb.RangeID, eCache *raftEntryCache, i uint64,
) (uint64, error) {
// entries() accepts a `nil` sideloaded storage and will skip inlining of
// sideloaded entries. We only need the term, so this is what we do.
ents, err := entries(ctx, eng, rangeID, eCache, nil /* sideloaded */, i, i+1, 0)
if err == raft.ErrCompacted {
ts, err := loadTruncatedState(ctx, eng, rangeID)
if err != nil {
return 0, err
}
if i == ts.Index {
return ts.Term, nil
}
return 0, raft.ErrCompacted
} else if err != nil {
return 0, err
}
if len(ents) == 0 {
return 0, nil
}
return ents[0].Term, nil
}
// LastIndex implements the raft.Storage interface.
func (r *replicaRaftStorage) LastIndex() (uint64, error) {
return r.mu.lastIndex, nil
}
// raftLastIndexLocked requires that r.mu is held.
func (r *Replica) raftLastIndexLocked() (uint64, error) {
return (*replicaRaftStorage)(r).LastIndex()
}
// raftTruncatedStateLocked returns metadata about the log that preceded the
// first current entry. This includes both entries that have been compacted away
// and the dummy entries that make up the starting point of an empty log.
// raftTruncatedStateLocked requires that r.mu is held.
func (r *Replica) raftTruncatedStateLocked(
ctx context.Context,
) (roachpb.RaftTruncatedState, error) {
if r.mu.state.TruncatedState != nil {
return *r.mu.state.TruncatedState, nil
}
ts, err := r.mu.stateLoader.loadTruncatedState(ctx, r.store.Engine())
if err != nil {
return ts, err
}
if ts.Index != 0 {
r.mu.state.TruncatedState = &ts
}
return ts, nil
}
// FirstIndex implements the raft.Storage interface.
func (r *replicaRaftStorage) FirstIndex() (uint64, error) {
ctx := r.AnnotateCtx(context.TODO())
ts, err := (*Replica)(r).raftTruncatedStateLocked(ctx)
if err != nil {
return 0, err
}
return ts.Index + 1, nil
}
// raftFirstIndexLocked requires that r.mu is held.
func (r *Replica) raftFirstIndexLocked() (uint64, error) {
return (*replicaRaftStorage)(r).FirstIndex()
}
// GetFirstIndex is the same function as raftFirstIndexLocked but it requires
// that r.mu is not held.
func (r *Replica) GetFirstIndex() (uint64, error) {
r.mu.Lock()
defer r.mu.Unlock()
return r.raftFirstIndexLocked()
}
// Snapshot implements the raft.Storage interface. Snapshot requires that
// r.mu is held. Note that the returned snapshot is a placeholder and
// does not contain any of the replica data. The snapshot is actually generated
// (and sent) by the Raft snapshot queue.
func (r *replicaRaftStorage) Snapshot() (raftpb.Snapshot, error) {
r.mu.AssertHeld()
appliedIndex := r.mu.state.RaftAppliedIndex
term, err := r.Term(appliedIndex)
if err != nil {
return raftpb.Snapshot{}, err
}
return raftpb.Snapshot{
Metadata: raftpb.SnapshotMetadata{
Index: appliedIndex,
Term: term,
},
}, nil
}
// raftSnapshotLocked requires that r.mu is held.
func (r *Replica) raftSnapshotLocked() (raftpb.Snapshot, error) {
return (*replicaRaftStorage)(r).Snapshot()
}
// GetSnapshot returns a snapshot of the replica appropriate for sending to a
// replica. If this method returns without error, callers must eventually call
// OutgoingSnapshot.Close.
func (r *Replica) GetSnapshot(
ctx context.Context, snapType string,
) (_ *OutgoingSnapshot, err error) {
// Get a snapshot while holding raftMu to make sure we're not seeing "half
// an AddSSTable" (i.e. a state in which an SSTable has been linked in, but
// the corresponding Raft command not applied yet).
r.raftMu.Lock()
snap := r.store.engine.NewSnapshot()
r.raftMu.Unlock()
defer func() {
if err != nil {
snap.Close()
}
}()
r.mu.RLock()
defer r.mu.RUnlock()
rangeID := r.RangeID
if r.exceedsDoubleSplitSizeRLocked() {
maxBytes := r.mu.maxBytes
size := r.mu.state.Stats.Total()
err := errors.Errorf(
"%s: not generating %s snapshot because replica is too large: %d > 2 * %d",
r, snapType, size, maxBytes)
return nil, err
}
startKey := r.mu.state.Desc.StartKey
ctx, sp := r.AnnotateCtxWithSpan(ctx, "snapshot")
defer sp.Finish()
log.Eventf(ctx, "new engine snapshot for replica %s", r)
// Delegate to a static function to make sure that we do not depend
// on any indirect calls to r.store.Engine() (or other in-memory
// state of the Replica). Everything must come from the snapshot.
withSideloaded := func(fn func(sideloadStorage) error) error {
r.raftMu.Lock()
defer r.raftMu.Unlock()
return fn(r.raftMu.sideloaded)
}
snapData, err := snapshot(
ctx, snapType, snap, rangeID, r.store.raftEntryCache, withSideloaded, startKey,
)
if err != nil {
log.Errorf(ctx, "error generating snapshot: %s", err)
return nil, err
}
return &snapData, nil
}
// OutgoingSnapshot contains the data required to stream a snapshot to a
// recipient. Once one is created, it needs to be closed via Close() to prevent
// resource leakage.
type OutgoingSnapshot struct {
SnapUUID uuid.UUID
// The Raft snapshot message to send. Contains SnapUUID as its data.
RaftSnap raftpb.Snapshot
// The RocksDB snapshot that will be streamed from.
EngineSnap engine.Reader
// The complete range iterator for the snapshot to stream.
Iter *ReplicaDataIterator
// The replica state within the snapshot.
State storagebase.ReplicaState
// Allows access the the original Replica's sideloaded storage. Note that
// this isn't a snapshot of the sideloaded storage congruent with EngineSnap
// or RaftSnap -- a log truncation could have removed files from the
// sideloaded storage in the meantime.
WithSideloaded func(func(sideloadStorage) error) error
RaftEntryCache *raftEntryCache
}
// Close releases the resources associated with the snapshot.
func (s *OutgoingSnapshot) Close() {
s.Iter.Close()
s.EngineSnap.Close()
}
// IncomingSnapshot contains the data for an incoming streaming snapshot message.
type IncomingSnapshot struct {
SnapUUID uuid.UUID
// The RocksDB BatchReprs that make up this snapshot.
Batches [][]byte
// The Raft log entries for this snapshot.
LogEntries [][]byte
// The replica state at the time the snapshot was generated (never nil).
State *storagebase.ReplicaState
snapType string
}
// snapshot creates an OutgoingSnapshot containing a rocksdb snapshot for the
// given range. Note that snapshot() is called without Replica.raftMu held.
func snapshot(
ctx context.Context,
snapType string,
snap engine.Reader,
rangeID roachpb.RangeID,
eCache *raftEntryCache,
withSideloaded func(func(sideloadStorage) error) error,
startKey roachpb.RKey,
) (OutgoingSnapshot, error) {
var desc roachpb.RangeDescriptor
// We ignore intents on the range descriptor (consistent=false) because we
// know they cannot be committed yet; operations that modify range
// descriptors resolve their own intents when they commit.
ok, err := engine.MVCCGetProto(ctx, snap, keys.RangeDescriptorKey(startKey),
hlc.MaxTimestamp, false /* !consistent */, nil, &desc)
if err != nil {
return OutgoingSnapshot{}, errors.Errorf("failed to get desc: %s", err)
}
if !ok {
return OutgoingSnapshot{}, errors.Errorf("couldn't find range descriptor")
}
var snapData roachpb.RaftSnapshotData
// Store RangeDescriptor as metadata, it will be retrieved by ApplySnapshot()
snapData.RangeDescriptor = desc
// Read the range metadata from the snapshot instead of the members
// of the Range struct because they might be changed concurrently.
appliedIndex, _, err := loadAppliedIndex(ctx, snap, rangeID)
if err != nil {
return OutgoingSnapshot{}, err
}
// Synthesize our raftpb.ConfState from desc.
var cs raftpb.ConfState
for _, rep := range desc.Replicas {
cs.Nodes = append(cs.Nodes, uint64(rep.ReplicaID))
}
term, err := term(ctx, snap, rangeID, eCache, appliedIndex)
if err != nil {
return OutgoingSnapshot{}, errors.Errorf("failed to fetch term of %d: %s", appliedIndex, err)
}
rsl := makeReplicaStateLoader(rangeID)
state, err := rsl.load(ctx, snap, &desc)
if err != nil {
return OutgoingSnapshot{}, err
}
// Intentionally let this iterator and the snapshot escape so that the
// streamer can send chunks from it bit by bit.
iter := NewReplicaDataIterator(&desc, snap, true /* replicatedOnly */)
snapUUID := uuid.MakeV4()
log.Infof(ctx, "generated %s snapshot %s at index %d",
snapType, snapUUID.Short(), appliedIndex)
return OutgoingSnapshot{
RaftEntryCache: eCache,
WithSideloaded: withSideloaded,
EngineSnap: snap,
Iter: iter,
State: state,
SnapUUID: snapUUID,
RaftSnap: raftpb.Snapshot{
Data: snapUUID.GetBytes(),
Metadata: raftpb.SnapshotMetadata{
Index: appliedIndex,
Term: term,
ConfState: cs,
},
},
}, nil
}
// append the given entries to the raft log. Takes the previous values of
// r.mu.lastIndex, r.mu.lastTerm, and r.mu.raftLogSize, and returns new values.
// We do this rather than modifying them directly because these modifications
// need to be atomic with the commit of the batch. This method requires that
// r.raftMu is held.
//
// append is intentionally oblivious to the existence of sideloaded proposals.
// They are managed by the caller, including cleaning up obsolete on-disk
// payloads in case the log tail is replaced.
func (r *Replica) append(
ctx context.Context,
batch engine.ReadWriter,
prevLastIndex uint64,
prevLastTerm uint64,
prevRaftLogSize int64,
entries []raftpb.Entry,
) (uint64, uint64, int64, error) {
if len(entries) == 0 {
return prevLastIndex, prevLastTerm, prevRaftLogSize, nil
}
var diff enginepb.MVCCStats
var value roachpb.Value
for i := range entries {
ent := &entries[i]
key := r.raftMu.stateLoader.RaftLogKey(ent.Index)
if err := value.SetProto(ent); err != nil {
return 0, 0, 0, err
}
value.InitChecksum(key)
var err error
if ent.Index > prevLastIndex {
err = engine.MVCCBlindPut(ctx, batch, &diff, key, hlc.Timestamp{}, value, nil /* txn */)
} else {
err = engine.MVCCPut(ctx, batch, &diff, key, hlc.Timestamp{}, value, nil /* txn */)
}
if err != nil {
return 0, 0, 0, err
}
}
// Delete any previously appended log entries which never committed.
lastIndex := entries[len(entries)-1].Index
lastTerm := entries[len(entries)-1].Term
for i := lastIndex + 1; i <= prevLastIndex; i++ {
// Note that the caller is in charge of deleting any sideloaded payloads
// (which they must only do *after* the batch has committed).
err := engine.MVCCDelete(ctx, batch, &diff, r.raftMu.stateLoader.RaftLogKey(i),
hlc.Timestamp{}, nil /* txn */)
if err != nil {
return 0, 0, 0, err
}
}
if err := r.raftMu.stateLoader.setLastIndex(ctx, batch, lastIndex); err != nil {
return 0, 0, 0, err
}
raftLogSize := prevRaftLogSize + diff.SysBytes
return lastIndex, lastTerm, raftLogSize, nil
}
// updateRangeInfo is called whenever a range is updated by ApplySnapshot
// or is created by range splitting to setup the fields which are
// uninitialized or need updating.
func (r *Replica) updateRangeInfo(desc *roachpb.RangeDescriptor) error {
// RangeMaxBytes should be updated by looking up Zone Config in two cases:
// 1. After applying a snapshot, if the zone config was not updated for
// this key range, then maxBytes of this range will not be updated either.
// 2. After a new range is created by a split, only copying maxBytes from
// the original range wont work as the original and new ranges might belong
// to different zones.
// Load the system config.
cfg, ok := r.store.Gossip().GetSystemConfig()
if !ok {
// This could be before the system config was ever gossiped,
// or it expired. Let the gossip callback set the info.
ctx := r.AnnotateCtx(context.TODO())
log.Warningf(ctx, "no system config available, cannot determine range MaxBytes")
return nil
}
// Find zone config for this range.
zone, err := cfg.GetZoneConfigForKey(desc.StartKey)
if err != nil {
return errors.Errorf("%s: failed to lookup zone config: %s", r, err)
}
r.SetMaxBytes(zone.RangeMaxBytes)
return nil
}
const (
snapTypeRaft = "Raft"
snapTypePreemptive = "preemptive"
)
func clearRangeData(
ctx context.Context,
desc *roachpb.RangeDescriptor,
keyCount int64,
eng engine.Engine,
batch engine.Batch,
) error {
iter := eng.NewIterator(false)
defer iter.Close()
// It is expensive for there to be many range deletion tombstones in the same
// sstable because all of the tombstones in an sstable are loaded whenever the
// sstable is accessed. So we avoid using range deletion unless there is some
// minimum number of keys. The value here was pulled out of thin air. It might
// be better to make this dependent on the size of the data being deleted. Or
// perhaps we should fix RocksDB to handle large numbers of tombstones in an
// sstable better.
const clearRangeMinKeys = 64
const metadataRanges = 2
for i, keyRange := range makeAllKeyRanges(desc) {
// Metadata ranges always have too few keys to justify ClearRange (see
// above), but the data range's key count needs to be explicitly checked.
var err error
if i >= metadataRanges && keyCount >= clearRangeMinKeys {
err = batch.ClearRange(keyRange.start, keyRange.end)
} else {
err = batch.ClearIterRange(iter, keyRange.start, keyRange.end)
}
if err != nil {
return err
}
}
return nil
}
// applySnapshot updates the replica based on the given snapshot and associated
// HardState (which may be empty, as Raft may apply some snapshots which don't
// require an update to the HardState). All snapshots must pass through Raft
// for correctness, i.e. the parameters to this method must be taken from
// a raft.Ready. It is the caller's responsibility to call
// r.store.processRangeDescriptorUpdate(r) after a successful applySnapshot.
// This method requires that r.raftMu is held.
func (r *Replica) applySnapshot(
ctx context.Context, inSnap IncomingSnapshot, snap raftpb.Snapshot, hs raftpb.HardState,
) (err error) {
s := *inSnap.State
if s.Desc.RangeID != r.RangeID {
log.Fatalf(ctx, "unexpected range ID %d", s.Desc.RangeID)
}
r.mu.RLock()
raftLogSize := r.mu.raftLogSize
replicaID := r.mu.replicaID
keyCount := r.mu.state.Stats.KeyCount
r.mu.RUnlock()
snapType := inSnap.snapType
defer func() {
if err == nil {
if snapType == snapTypeRaft {
r.store.metrics.RangeSnapshotsNormalApplied.Inc(1)
} else {
r.store.metrics.RangeSnapshotsPreemptiveApplied.Inc(1)
}
}
}()
if raft.IsEmptySnap(snap) {
// Raft discarded the snapshot, indicating that our local state is
// already ahead of what the snapshot provides. But we count it for
// stats (see the defer above).
return nil
}
var stats struct {
clear time.Time
batch time.Time
entries time.Time
commit time.Time
}
var size int
for _, b := range inSnap.Batches {
size += len(b)
}
for _, e := range inSnap.LogEntries {
size += len(e)
}
log.Infof(ctx, "applying %s snapshot at index %d "+
"(id=%s, encoded size=%d, %d rocksdb batches, %d log entries)",
snapType, snap.Metadata.Index, inSnap.SnapUUID.Short(),
size, len(inSnap.Batches), len(inSnap.LogEntries))
defer func(start time.Time) {
now := timeutil.Now()
log.Infof(ctx, "applied %s snapshot in %0.0fms [clear=%0.0fms batch=%0.0fms entries=%0.0fms commit=%0.0fms]",
snapType, now.Sub(start).Seconds()*1000,
stats.clear.Sub(start).Seconds()*1000,
stats.batch.Sub(stats.clear).Seconds()*1000,
stats.entries.Sub(stats.batch).Seconds()*1000,
stats.commit.Sub(stats.entries).Seconds()*1000)
}(timeutil.Now())
// Use a more efficient write-only batch because we don't need to do any
// reads from the batch.
batch := r.store.Engine().NewWriteOnlyBatch()
defer batch.Close()
// Delete everything in the range and recreate it from the snapshot.
// We need to delete any old Raft log entries here because any log entries
// that predate the snapshot will be orphaned and never truncated or GC'd.
if err := clearRangeData(ctx, s.Desc, keyCount, r.store.Engine(), batch); err != nil {
return err
}
stats.clear = timeutil.Now()
// Write the snapshot into the range.
for _, batchRepr := range inSnap.Batches {
if err := batch.ApplyBatchRepr(batchRepr, false); err != nil {
return err
}
}
// The log entries are all written to distinct keys so we can use a
// distinct batch.
distinctBatch := batch.Distinct()
stats.batch = timeutil.Now()
logEntries := make([]raftpb.Entry, len(inSnap.LogEntries))
for i, bytes := range inSnap.LogEntries {
if err := logEntries[i].Unmarshal(bytes); err != nil {
return err
}
}
// If this replica doesn't know its ReplicaID yet, we're applying a
// preemptive snapshot. In this case, we're going to have to write the
// sideloaded proposals into the Raft log. Otherwise, sideload.
thinEntries := logEntries
if replicaID != 0 {
var err error
var sideloadedEntriesSize int64
thinEntries, sideloadedEntriesSize, err = r.maybeSideloadEntriesRaftMuLocked(ctx, logEntries)
if err != nil {
return err
}
raftLogSize += sideloadedEntriesSize
}
// Write the snapshot's Raft log into the range.
_, _, raftLogSize, err = r.append(
ctx, distinctBatch, 0, 0, raftLogSize, thinEntries,
)
if err != nil {
return err
}
stats.entries = timeutil.Now()
// Note that we don't require that Raft supply us with a nonempty HardState
// on a snapshot. We don't want to make that assumption because it's not
// guaranteed by the contract. Raft *must* send us a HardState when it
// increases the committed index as a result of the snapshot, but who is to
// say it isn't going to accept a snapshot which is identical to the current
// state?
//
// Note that since this snapshot comes from Raft, we don't have to synthesize
// the HardState -- Raft wouldn't ask us to update the HardState in incorrect
// ways.
if !raft.IsEmptyHardState(hs) {
if err := r.raftMu.stateLoader.setHardState(ctx, distinctBatch, hs); err != nil {
return errors.Wrapf(err, "unable to persist HardState %+v", &hs)
}
}
// We need to close the distinct batch and start using the normal batch for
// the read below.
distinctBatch.Close()
// As outlined above, last and applied index are the same after applying
// the snapshot (i.e. the snapshot has no uncommitted tail).
if s.RaftAppliedIndex != snap.Metadata.Index {
log.Fatalf(ctx, "snapshot RaftAppliedIndex %d doesn't match its metadata index %d",
s.RaftAppliedIndex, snap.Metadata.Index)
}
// We've written Raft log entries, so we need to sync the WAL.
if err := batch.Commit(syncRaftLog.Get(&r.store.cfg.Settings.SV)); err != nil {
return err
}
stats.commit = timeutil.Now()
r.mu.Lock()
// We set the persisted last index to the last applied index. This is
// not a correctness issue, but means that we may have just transferred
// some entries we're about to re-request from the leader and overwrite.
// However, raft.MultiNode currently expects this behaviour, and the
// performance implications are not likely to be drastic. If our
// feelings about this ever change, we can add a LastIndex field to
// raftpb.SnapshotMetadata.
r.mu.lastIndex = s.RaftAppliedIndex
// We could recompute and return the lastTerm in the snapshot, but instead we
// just set an invalid term and force a recomputation later.
r.mu.lastTerm = invalidLastTerm
r.mu.raftLogSize = raftLogSize
// Update the range and store stats.
r.store.metrics.subtractMVCCStats(r.mu.state.Stats)
r.store.metrics.addMVCCStats(s.Stats)
r.mu.state = s
r.assertStateLocked(ctx, r.store.Engine())
r.mu.Unlock()
// As the last deferred action after committing the batch, update other
// fields which are uninitialized or need updating. This may not happen
// if the system config has not yet been loaded. While config update
// will correctly set the fields, there is no order guarantee in
// ApplySnapshot.
// TODO: should go through the standard store lock when adding a replica.
if err := r.updateRangeInfo(s.Desc); err != nil {
panic(err)
}
r.setDescWithoutProcessUpdate(s.Desc)
return nil
}
type raftCommandEncodingVersion byte
// Raft commands are encoded with a 1-byte version (currently 0 or 1), an 8-byte
// ID, followed by the payload. This inflexible encoding is used so we can
// efficiently parse the command id while processing the logs.
//
// TODO(bdarnell): is this commandID still appropriate for our needs?
const (
// The prescribed length for each command ID.
raftCommandIDLen = 8
// The initial Raft command version, used for all regular Raft traffic.
raftVersionStandard raftCommandEncodingVersion = 0
// A proposal containing an SSTable which preferably should be sideloaded
// (i.e. not stored in the Raft log wholesale). Can be treated as a regular
// proposal when arriving on the wire, but when retrieved from the local
// Raft log it necessary to inline the payload first as it has usually
// been sideloaded.
raftVersionSideloaded raftCommandEncodingVersion = 1
// The no-split bit is now unused, but we still apply the mask to the first
// byte of the command for backward compatibility.
//
// TODO(tschottdorf): predates v1.0 by a significant margin. Remove.
raftCommandNoSplitBit = 1 << 7
raftCommandNoSplitMask = raftCommandNoSplitBit - 1
)
func encodeRaftCommandV1(commandID storagebase.CmdIDKey, command []byte) []byte {
return encodeRaftCommand(raftVersionStandard, commandID, command)
}
func encodeRaftCommandV2(commandID storagebase.CmdIDKey, command []byte) []byte {
return encodeRaftCommand(raftVersionSideloaded, commandID, command)
}
// encode a command ID, an encoded storagebase.RaftCommand, and
// whether the command contains a split.
func encodeRaftCommand(
version raftCommandEncodingVersion, commandID storagebase.CmdIDKey, command []byte,
) []byte {
if len(commandID) != raftCommandIDLen {
panic(fmt.Sprintf("invalid command ID length; %d != %d", len(commandID), raftCommandIDLen))
}
x := make([]byte, 1, 1+raftCommandIDLen+len(command))
x[0] = byte(version)
x = append(x, []byte(commandID)...)
x = append(x, command...)
return x
}
// DecodeRaftCommand splits a raftpb.Entry.Data into its commandID and
// command portions. The caller is responsible for checking that the data
// is not empty (which indicates a dummy entry generated by raft rather
// than a real command). Usage is mostly internal to the storage package
// but is exported for use by debugging tools.
func DecodeRaftCommand(data []byte) (storagebase.CmdIDKey, []byte) {
v := raftCommandEncodingVersion(data[0] & raftCommandNoSplitMask)
if v != raftVersionStandard && v != raftVersionSideloaded {
panic(fmt.Sprintf("unknown command encoding version %v", data[0]))
}
return storagebase.CmdIDKey(data[1 : 1+raftCommandIDLen]), data[1+raftCommandIDLen:]
}