With CoreDNS now supporting etcdv3 as the DNS backend, we can update our federation target to etcdv3. Users will now be able to use etcdv3 server as the federation backbone. Minio will update bucket data to etcdv3 and CoreDNS can pick that data up and serve it as bucket style DNS path.
358 lines
9.9 KiB
Go
358 lines
9.9 KiB
Go
// Copyright 2015 The etcd Authors
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//
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// Licensed under the Apache License, Version 2.0 (the "License");
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// you may not use this file except in compliance with the License.
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// You may obtain a copy of the License at
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//
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// http://www.apache.org/licenses/LICENSE-2.0
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//
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// Unless required by applicable law or agreed to in writing, software
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// distributed under the License is distributed on an "AS IS" BASIS,
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// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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// See the License for the specific language governing permissions and
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// limitations under the License.
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package raft
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import (
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"fmt"
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"log"
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pb "github.com/coreos/etcd/raft/raftpb"
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)
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type raftLog struct {
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// storage contains all stable entries since the last snapshot.
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storage Storage
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// unstable contains all unstable entries and snapshot.
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// they will be saved into storage.
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unstable unstable
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// committed is the highest log position that is known to be in
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// stable storage on a quorum of nodes.
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committed uint64
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// applied is the highest log position that the application has
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// been instructed to apply to its state machine.
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// Invariant: applied <= committed
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applied uint64
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logger Logger
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}
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// newLog returns log using the given storage. It recovers the log to the state
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// that it just commits and applies the latest snapshot.
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func newLog(storage Storage, logger Logger) *raftLog {
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if storage == nil {
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log.Panic("storage must not be nil")
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}
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log := &raftLog{
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storage: storage,
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logger: logger,
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}
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firstIndex, err := storage.FirstIndex()
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if err != nil {
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panic(err) // TODO(bdarnell)
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}
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lastIndex, err := storage.LastIndex()
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if err != nil {
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panic(err) // TODO(bdarnell)
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}
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log.unstable.offset = lastIndex + 1
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log.unstable.logger = logger
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// Initialize our committed and applied pointers to the time of the last compaction.
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log.committed = firstIndex - 1
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log.applied = firstIndex - 1
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return log
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}
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func (l *raftLog) String() string {
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return fmt.Sprintf("committed=%d, applied=%d, unstable.offset=%d, len(unstable.Entries)=%d", l.committed, l.applied, l.unstable.offset, len(l.unstable.entries))
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}
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// maybeAppend returns (0, false) if the entries cannot be appended. Otherwise,
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// it returns (last index of new entries, true).
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func (l *raftLog) maybeAppend(index, logTerm, committed uint64, ents ...pb.Entry) (lastnewi uint64, ok bool) {
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if l.matchTerm(index, logTerm) {
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lastnewi = index + uint64(len(ents))
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ci := l.findConflict(ents)
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switch {
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case ci == 0:
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case ci <= l.committed:
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l.logger.Panicf("entry %d conflict with committed entry [committed(%d)]", ci, l.committed)
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default:
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offset := index + 1
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l.append(ents[ci-offset:]...)
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}
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l.commitTo(min(committed, lastnewi))
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return lastnewi, true
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}
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return 0, false
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}
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func (l *raftLog) append(ents ...pb.Entry) uint64 {
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if len(ents) == 0 {
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return l.lastIndex()
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}
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if after := ents[0].Index - 1; after < l.committed {
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l.logger.Panicf("after(%d) is out of range [committed(%d)]", after, l.committed)
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}
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l.unstable.truncateAndAppend(ents)
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return l.lastIndex()
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}
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// findConflict finds the index of the conflict.
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// It returns the first pair of conflicting entries between the existing
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// entries and the given entries, if there are any.
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// If there is no conflicting entries, and the existing entries contains
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// all the given entries, zero will be returned.
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// If there is no conflicting entries, but the given entries contains new
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// entries, the index of the first new entry will be returned.
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// An entry is considered to be conflicting if it has the same index but
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// a different term.
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// The first entry MUST have an index equal to the argument 'from'.
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// The index of the given entries MUST be continuously increasing.
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func (l *raftLog) findConflict(ents []pb.Entry) uint64 {
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for _, ne := range ents {
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if !l.matchTerm(ne.Index, ne.Term) {
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if ne.Index <= l.lastIndex() {
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l.logger.Infof("found conflict at index %d [existing term: %d, conflicting term: %d]",
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ne.Index, l.zeroTermOnErrCompacted(l.term(ne.Index)), ne.Term)
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}
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return ne.Index
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}
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}
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return 0
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}
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func (l *raftLog) unstableEntries() []pb.Entry {
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if len(l.unstable.entries) == 0 {
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return nil
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}
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return l.unstable.entries
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}
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// nextEnts returns all the available entries for execution.
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// If applied is smaller than the index of snapshot, it returns all committed
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// entries after the index of snapshot.
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func (l *raftLog) nextEnts() (ents []pb.Entry) {
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off := max(l.applied+1, l.firstIndex())
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if l.committed+1 > off {
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ents, err := l.slice(off, l.committed+1, noLimit)
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if err != nil {
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l.logger.Panicf("unexpected error when getting unapplied entries (%v)", err)
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}
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return ents
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}
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return nil
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}
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// hasNextEnts returns if there is any available entries for execution. This
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// is a fast check without heavy raftLog.slice() in raftLog.nextEnts().
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func (l *raftLog) hasNextEnts() bool {
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off := max(l.applied+1, l.firstIndex())
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return l.committed+1 > off
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}
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func (l *raftLog) snapshot() (pb.Snapshot, error) {
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if l.unstable.snapshot != nil {
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return *l.unstable.snapshot, nil
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}
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return l.storage.Snapshot()
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}
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func (l *raftLog) firstIndex() uint64 {
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if i, ok := l.unstable.maybeFirstIndex(); ok {
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return i
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}
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index, err := l.storage.FirstIndex()
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if err != nil {
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panic(err) // TODO(bdarnell)
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}
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return index
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}
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func (l *raftLog) lastIndex() uint64 {
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if i, ok := l.unstable.maybeLastIndex(); ok {
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return i
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}
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i, err := l.storage.LastIndex()
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if err != nil {
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panic(err) // TODO(bdarnell)
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}
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return i
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}
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func (l *raftLog) commitTo(tocommit uint64) {
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// never decrease commit
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if l.committed < tocommit {
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if l.lastIndex() < tocommit {
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l.logger.Panicf("tocommit(%d) is out of range [lastIndex(%d)]. Was the raft log corrupted, truncated, or lost?", tocommit, l.lastIndex())
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}
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l.committed = tocommit
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}
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}
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func (l *raftLog) appliedTo(i uint64) {
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if i == 0 {
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return
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}
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if l.committed < i || i < l.applied {
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l.logger.Panicf("applied(%d) is out of range [prevApplied(%d), committed(%d)]", i, l.applied, l.committed)
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}
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l.applied = i
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}
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func (l *raftLog) stableTo(i, t uint64) { l.unstable.stableTo(i, t) }
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func (l *raftLog) stableSnapTo(i uint64) { l.unstable.stableSnapTo(i) }
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func (l *raftLog) lastTerm() uint64 {
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t, err := l.term(l.lastIndex())
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if err != nil {
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l.logger.Panicf("unexpected error when getting the last term (%v)", err)
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}
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return t
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}
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func (l *raftLog) term(i uint64) (uint64, error) {
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// the valid term range is [index of dummy entry, last index]
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dummyIndex := l.firstIndex() - 1
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if i < dummyIndex || i > l.lastIndex() {
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// TODO: return an error instead?
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return 0, nil
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}
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if t, ok := l.unstable.maybeTerm(i); ok {
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return t, nil
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}
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t, err := l.storage.Term(i)
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if err == nil {
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return t, nil
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}
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if err == ErrCompacted || err == ErrUnavailable {
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return 0, err
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}
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panic(err) // TODO(bdarnell)
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}
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func (l *raftLog) entries(i, maxsize uint64) ([]pb.Entry, error) {
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if i > l.lastIndex() {
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return nil, nil
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}
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return l.slice(i, l.lastIndex()+1, maxsize)
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}
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// allEntries returns all entries in the log.
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func (l *raftLog) allEntries() []pb.Entry {
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ents, err := l.entries(l.firstIndex(), noLimit)
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if err == nil {
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return ents
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}
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if err == ErrCompacted { // try again if there was a racing compaction
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return l.allEntries()
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}
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// TODO (xiangli): handle error?
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panic(err)
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}
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// isUpToDate determines if the given (lastIndex,term) log is more up-to-date
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// by comparing the index and term of the last entries in the existing logs.
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// If the logs have last entries with different terms, then the log with the
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// later term is more up-to-date. If the logs end with the same term, then
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// whichever log has the larger lastIndex is more up-to-date. If the logs are
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// the same, the given log is up-to-date.
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func (l *raftLog) isUpToDate(lasti, term uint64) bool {
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return term > l.lastTerm() || (term == l.lastTerm() && lasti >= l.lastIndex())
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}
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func (l *raftLog) matchTerm(i, term uint64) bool {
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t, err := l.term(i)
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if err != nil {
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return false
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}
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return t == term
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}
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func (l *raftLog) maybeCommit(maxIndex, term uint64) bool {
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if maxIndex > l.committed && l.zeroTermOnErrCompacted(l.term(maxIndex)) == term {
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l.commitTo(maxIndex)
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return true
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}
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return false
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}
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func (l *raftLog) restore(s pb.Snapshot) {
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l.logger.Infof("log [%s] starts to restore snapshot [index: %d, term: %d]", l, s.Metadata.Index, s.Metadata.Term)
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l.committed = s.Metadata.Index
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l.unstable.restore(s)
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}
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// slice returns a slice of log entries from lo through hi-1, inclusive.
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func (l *raftLog) slice(lo, hi, maxSize uint64) ([]pb.Entry, error) {
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err := l.mustCheckOutOfBounds(lo, hi)
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if err != nil {
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return nil, err
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}
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if lo == hi {
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return nil, nil
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}
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var ents []pb.Entry
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if lo < l.unstable.offset {
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storedEnts, err := l.storage.Entries(lo, min(hi, l.unstable.offset), maxSize)
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if err == ErrCompacted {
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return nil, err
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} else if err == ErrUnavailable {
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l.logger.Panicf("entries[%d:%d) is unavailable from storage", lo, min(hi, l.unstable.offset))
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} else if err != nil {
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panic(err) // TODO(bdarnell)
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}
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// check if ents has reached the size limitation
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if uint64(len(storedEnts)) < min(hi, l.unstable.offset)-lo {
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return storedEnts, nil
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}
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ents = storedEnts
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}
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if hi > l.unstable.offset {
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unstable := l.unstable.slice(max(lo, l.unstable.offset), hi)
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if len(ents) > 0 {
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ents = append([]pb.Entry{}, ents...)
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ents = append(ents, unstable...)
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} else {
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ents = unstable
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}
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}
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return limitSize(ents, maxSize), nil
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}
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// l.firstIndex <= lo <= hi <= l.firstIndex + len(l.entries)
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func (l *raftLog) mustCheckOutOfBounds(lo, hi uint64) error {
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if lo > hi {
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l.logger.Panicf("invalid slice %d > %d", lo, hi)
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}
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fi := l.firstIndex()
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if lo < fi {
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return ErrCompacted
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}
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length := l.lastIndex() + 1 - fi
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if lo < fi || hi > fi+length {
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l.logger.Panicf("slice[%d,%d) out of bound [%d,%d]", lo, hi, fi, l.lastIndex())
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}
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return nil
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}
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func (l *raftLog) zeroTermOnErrCompacted(t uint64, err error) uint64 {
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if err == nil {
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return t
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}
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if err == ErrCompacted {
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return 0
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}
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l.logger.Panicf("unexpected error (%v)", err)
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return 0
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}
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