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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 (
"context"
"fmt"
"math"
"sync/atomic"
"time"
"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/raftentry"
"github.com/cockroachdb/cockroach/pkg/storage/rditer"
"github.com/cockroachdb/cockroach/pkg/storage/stateloader"
"github.com/cockroachdb/cockroach/pkg/storage/storagebase"
"github.com/cockroachdb/cockroach/pkg/storage/storagepb"
"github.com/cockroachdb/cockroach/pkg/util/hlc"
"github.com/cockroachdb/cockroach/pkg/util/log"
"github.com/cockroachdb/cockroach/pkg/util/protoutil"
"github.com/cockroachdb/cockroach/pkg/util/timeutil"
"github.com/cockroachdb/cockroach/pkg/util/uuid"
"github.com/pkg/errors"
"go.etcd.io/etcd/raft"
"go.etcd.io/etcd/raft/raftpb"
)
// 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. 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())
if r.raftMu.sideloaded == nil {
return nil, errors.New("sideloaded storage is uninitialized")
}
return entries(ctx, r.mu.stateLoader, 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,
rsl stateloader.StateLoader,
e engine.Reader,
rangeID roachpb.RangeID,
eCache *raftentry.Cache,
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, exceededMaxBytes := eCache.Scan(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 || exceededMaxBytes {
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
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())
if size > maxBytes {
exceededMaxBytes = true
if len(ents) > 0 {
return exceededMaxBytes, nil
}
}
ents = append(ents, ent)
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.Add(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 := rsl.LoadLastIndex(ctx, e)
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 := rsl.LoadRaftTruncatedState(ctx, e)
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{},
engine.MVCCScanOptions{},
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 e, ok := r.store.raftEntryCache.Get(r.RangeID, i); ok {
return e.Term, nil
}
readonly := r.store.Engine().NewReadOnly()
defer readonly.Close()
ctx := r.AnnotateCtx(context.TODO())
return term(ctx, r.mu.stateLoader, 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,
rsl stateloader.StateLoader,
eng engine.Reader,
rangeID roachpb.RangeID,
eCache *raftentry.Cache,
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, rsl, eng, rangeID, eCache, nil /* sideloaded */, i, i+1, math.MaxUint64 /* maxBytes */)
if err == raft.ErrCompacted {
ts, _, err := rsl.LoadRaftTruncatedState(ctx, eng)
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.LoadRaftTruncatedState(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()
}
// GetLeaseAppliedIndex returns the lease index of the last applied command.
func (r *Replica) GetLeaseAppliedIndex() uint64 {
r.mu.RLock()
defer r.mu.RUnlock()
return r.mu.state.LeaseAppliedIndex
}
// 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) {
snapUUID := uuid.MakeV4()
// 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.mu.Lock()
appliedIndex := r.mu.state.RaftAppliedIndex
r.addSnapshotLogTruncationConstraintLocked(ctx, snapUUID, appliedIndex) // cleared when OutgoingSnapshot closes
r.mu.Unlock()
r.raftMu.Unlock()
release := func() {
r.completeSnapshotLogTruncationConstraint(ctx, snapUUID, timeutil.Now())
}
defer func() {
if err != nil {
release()
snap.Close()
}
}()
r.mu.RLock()
defer r.mu.RUnlock()
rangeID := r.RangeID
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)
}
// NB: We have Replica.mu read-locked, but we need it write-locked in order
// to use Replica.mu.stateLoader. This call is not performance sensitive, so
// create a new state loader.
snapData, err := snapshot(
ctx, snapUUID, stateloader.Make(rangeID), snapType,
snap, rangeID, r.store.raftEntryCache, withSideloaded, startKey,
)
if err != nil {
log.Errorf(ctx, "error generating snapshot: %s", err)
return nil, err
}
snapData.onClose = release
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 *rditer.ReplicaDataIterator
// The replica state within the snapshot.
State storagepb.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 *raftentry.Cache
snapType string
onClose func()
}
func (s *OutgoingSnapshot) String() string {
return fmt.Sprintf("%s snapshot %s at applied index %d", s.snapType, s.SnapUUID.Short(), s.State.RaftAppliedIndex)
}
// Close releases the resources associated with the snapshot.
func (s *OutgoingSnapshot) Close() {
s.Iter.Close()
s.EngineSnap.Close()
if s.onClose != nil {
s.onClose()
}
}
// 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 *storagepb.ReplicaState
// When true, this snapshot contains a legacy replicated TruncatedState,
// meaning that the recipient must not write the new, unreplicated
// TruncatedState. It will be upgraded during the next log truncation
// (assuming cluster version is bumped at that point).
//
// See the comment on VersionUnreplicatedRaftTruncatedState for details.
UsesLegacyTruncatedState bool
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,
snapUUID uuid.UUID,
rsl stateloader.StateLoader,
snapType string,
snap engine.Reader,
rangeID roachpb.RangeID,
eCache *raftentry.Cache,
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, &desc, engine.MVCCGetOptions{Inconsistent: true})
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 := rsl.LoadAppliedIndex(ctx, snap)
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, rsl, snap, rangeID, eCache, appliedIndex)
if err != nil {
return OutgoingSnapshot{}, errors.Errorf("failed to fetch term of %d: %s", appliedIndex, err)
}
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 := rditer.NewReplicaDataIterator(&desc, snap, true /* replicatedOnly */)
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,
},
},
snapType: snapType,
}, 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
}
}
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 := r.store.Gossip().GetSystemConfig()
if cfg == nil {
// 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.SetZoneConfig(zone)
return nil
}
const (
snapTypeRaft = "Raft"
snapTypePreemptive = "preemptive"
)
func clearRangeData(
ctx context.Context,
desc *roachpb.RangeDescriptor,
eng engine.Reader,
batch engine.Batch,
destroyData bool,
) error {
iter := eng.NewIterator(engine.IterOptions{UpperBound: desc.EndKey.AsRawKey()})
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
keyRanges := rditer.MakeAllKeyRanges(desc)
if !destroyData {
// TODO(benesch): The fact that we hardcode the number of
// "metadata" ranges (i.e. non-user-keyspace) suggests that
// rditer.MakeAllKeyRanges has the wrong API.
keyRanges = keyRanges[:1]
}
for _, keyRange := range keyRanges {
// Peek into the range to see whether it's large enough to justify
// ClearRange. Note that the work done here is bounded by
// clearRangeMinKeys, so it will be fairly cheap even for large
// ranges.
//
// TODO(bdarnell): Move this into ClearIterRange so we don't have
// to do this scan twice.
count := 0
iter.Seek(keyRange.Start)
for {
valid, err := iter.Valid()
if err != nil {
return err
}
if !valid || !iter.Key().Less(keyRange.End) {
break
}
count++
if count > clearRangeMinKeys {
break
}
iter.Next()
}
var err error
if count > 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 and its store based on the given snapshot
// and associated HardState. All snapshots must pass through Raft for
// correctness, i.e. the parameters to this method must be taken from a
// raft.Ready. Any replicas specified in subsumedRepls will be destroyed
// atomically with the application of the snapshot.
//
// If there is a placeholder associated with r, applySnapshot will remove that
// placeholder from the store if and only if it does not return an error.
//
// This method requires that r.raftMu is held, as well as the raftMus of any
// replicas in subsumedRepls.
//
// TODO(benesch): the way this replica method reaches into its store to update
// replicasByKey is unfortunate, but the fix requires a substantial refactor to
// maintain the necessary synchronization.
func (r *Replica) applySnapshot(
ctx context.Context,
inSnap IncomingSnapshot,
snap raftpb.Snapshot,
hs raftpb.HardState,
subsumedRepls []*Replica,
) (err error) {
s := *inSnap.State
if s.Desc.RangeID != r.RangeID {
log.Fatalf(ctx, "unexpected range ID %d", s.Desc.RangeID)
}
r.mu.RLock()
replicaID := r.mu.replicaID
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).
//
// Since we're not returning an error, we're responsible for removing any
// placeholder that might exist.
r.store.mu.Lock()
if r.store.removePlaceholderLocked(ctx, r.RangeID) {
atomic.AddInt32(&r.store.counts.filledPlaceholders, 1)
}
r.store.mu.Unlock()
return nil
}
if raft.IsEmptyHardState(hs) {
// Raft will never provide an empty HardState if it is providing a
// nonempty snapshot because we discard snapshots that do not increase
// the commit index.
log.Fatalf(ctx, "found empty HardState for non-empty Snapshot %+v", snap)
}
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()
// If we're subsuming a replica below, we don't have its last NextReplicaID,
// nor can we obtain it. That's OK: we can just be conservative and use the
// maximum possible replica ID. preDestroyRaftMuLocked will write a replica
// tombstone using this maximum possible replica ID, which would normally be
// problematic, as it would prevent this store from ever having a new replica
// of the removed range. In this case, however, it's copacetic, as subsumed
// ranges _can't_ have new replicas.
const subsumedNextReplicaID = math.MaxInt32
// As part of applying the snapshot, we may need to subsume replicas that have
// been merged into this range. Destroy their data in the same batch in which
// we apply the snapshot.
for _, sr := range subsumedRepls {
if err := sr.preDestroyRaftMuLocked(
ctx, r.store.Engine(), batch, subsumedNextReplicaID, true, /* destroyData */
); err != nil {
return err
}
}
// 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, r.store.Engine(), batch, true /* destroyData */); 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()
if !inSnap.UsesLegacyTruncatedState {
// We're using the unreplicated truncated state, which we need to
// manually persist to disk. If we're not taking this branch, the
// snapshot contains a legacy TruncatedState and we don't need to do
// anything (in fact, must not -- the invariant is that exactly one of
// them exists at any given point in the state machine).
if err := stateloader.Make(s.Desc.RangeID).SetRaftTruncatedState(
ctx, distinctBatch, s.TruncatedState,
); err != nil {
return err
}
}
logEntries := make([]raftpb.Entry, len(inSnap.LogEntries))
for i, bytes := range inSnap.LogEntries {
if err := protoutil.Unmarshal(bytes, &logEntries[i]); 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.
var raftLogSize int64
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.
var lastTerm uint64
_, lastTerm, raftLogSize, err = r.append(
ctx, distinctBatch, 0, invalidLastTerm, raftLogSize, thinEntries,
)
if err != nil {
return err
}
stats.entries = timeutil.Now()
// 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 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(!disableSyncRaftLog.Get(&r.store.cfg.Settings.SV)); err != nil {
return err
}
stats.commit = timeutil.Now()
// The on-disk state is now committed, but the corresponding in-memory state
// has not yet been updated. Any errors past this point must therefore be
// treated as fatal.
for _, sr := range subsumedRepls {
// We removed sr's data when we committed the batch. Finish subsumption by
// updating the in-memory bookkeping.
if err := sr.postDestroyRaftMuLocked(ctx, sr.GetMVCCStats()); err != nil {
log.Fatalf(ctx, "unable to finish destroying %s while applying snapshot: %s", sr, err)
}
// We already hold sr's raftMu, so we must call removeReplicaImpl directly.
// Note that it's safe to update the store's metadata for sr's removal
// separately from updating the store's metadata for r's new descriptor
// (i.e., under a different store.mu acquisition). Each store.mu acquisition
// leaves the store in a consistent state, and access to the replicas
// themselves is protected by their raftMus, which are held from start to
// finish.
if err := r.store.removeReplicaImpl(ctx, sr, subsumedNextReplicaID, RemoveOptions{
DestroyData: false, // data is already destroyed
}); err != nil {
log.Fatalf(ctx, "unable to remove %s while applying snapshot: %s", sr, err)
}
}
// Atomically swap the placeholder, if any, for the replica, and update the
// replica's descriptor.
r.store.mu.Lock()
if r.store.removePlaceholderLocked(ctx, r.RangeID) {
atomic.AddInt32(&r.store.counts.filledPlaceholders, 1)
}
r.setDesc(ctx, s.Desc)
if err := r.store.maybeMarkReplicaInitializedLocked(ctx, r); err != nil {
log.Fatalf(ctx, "unable to mark replica initialized while applying snapshot: %s", err)
}
r.store.mu.Unlock()
// Invoke the leasePostApply method to ensure we properly initialize the
// replica according to whether it holds the lease. We allow jumps in the
// lease sequence because there may be multiple lease changes accounted for
// in the snapshot.
r.leasePostApply(ctx, *s.Lease, true /* permitJump */)
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 behavior, 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
r.mu.lastTerm = lastTerm
r.mu.raftLogSize = raftLogSize
// Update the store stats for the data in the snapshot.
r.store.metrics.subtractMVCCStats(*r.mu.state.Stats)
r.store.metrics.addMVCCStats(*s.Stats)
// Update the rest of the Raft state. Changes to r.mu.state.Desc must be
// managed by r.setDesc and changes to r.mu.state.Lease must be handled
// by r.leasePostApply, but we called those above, so now it's safe to
// wholesale replace r.mu.state.
r.mu.state = s
r.assertStateLocked(ctx, r.store.Engine())