mirror of
https://github.com/etcd-io/etcd.git
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124 lines
3.7 KiB
Go
124 lines
3.7 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 cindex
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import (
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"sync"
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"sync/atomic"
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"go.etcd.io/etcd/server/v3/storage/backend"
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"go.etcd.io/etcd/server/v3/storage/schema"
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)
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type Backend interface {
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BatchTx() backend.BatchTx
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}
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// ConsistentIndexer is an interface that wraps the Get/Set/Save method for consistentIndex.
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type ConsistentIndexer interface {
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// ConsistentIndex returns the consistent index of current executing entry.
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ConsistentIndex() uint64
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// SetConsistentIndex set the consistent index of current executing entry.
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SetConsistentIndex(v uint64, term uint64)
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// UnsafeSave must be called holding the lock on the tx.
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// It saves consistentIndex to the underlying stable storage.
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UnsafeSave(tx backend.BatchTx)
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// SetBackend set the available backend.BatchTx for ConsistentIndexer.
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SetBackend(be Backend)
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}
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// consistentIndex implements the ConsistentIndexer interface.
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type consistentIndex struct {
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// consistentIndex represents the offset of an entry in a consistent replica log.
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// It caches the "consistent_index" key's value.
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// Accessed through atomics so must be 64-bit aligned.
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consistentIndex uint64
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// term represents the RAFT term of committed entry in a consistent replica log.
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// Accessed through atomics so must be 64-bit aligned.
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// The value is being persisted in the backend since v3.5.
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term uint64
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// be is used for initial read consistentIndex
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be Backend
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// mutex is protecting be.
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mutex sync.Mutex
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}
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// NewConsistentIndex creates a new consistent index.
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// If `be` is nil, it must be set (SetBackend) before first access using `ConsistentIndex()`.
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func NewConsistentIndex(be Backend) ConsistentIndexer {
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return &consistentIndex{be: be}
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}
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func (ci *consistentIndex) ConsistentIndex() uint64 {
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if index := atomic.LoadUint64(&ci.consistentIndex); index > 0 {
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return index
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}
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ci.mutex.Lock()
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defer ci.mutex.Unlock()
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v, term := schema.ReadConsistentIndex(ci.be.BatchTx())
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ci.SetConsistentIndex(v, term)
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return v
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}
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func (ci *consistentIndex) SetConsistentIndex(v uint64, term uint64) {
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atomic.StoreUint64(&ci.consistentIndex, v)
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atomic.StoreUint64(&ci.term, term)
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}
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func (ci *consistentIndex) UnsafeSave(tx backend.BatchTx) {
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index := atomic.LoadUint64(&ci.consistentIndex)
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term := atomic.LoadUint64(&ci.term)
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schema.UnsafeUpdateConsistentIndex(tx, index, term, true)
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}
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func (ci *consistentIndex) SetBackend(be Backend) {
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ci.mutex.Lock()
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defer ci.mutex.Unlock()
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ci.be = be
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// After the backend is changed, the first access should re-read it.
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ci.SetConsistentIndex(0, 0)
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}
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func NewFakeConsistentIndex(index uint64) ConsistentIndexer {
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return &fakeConsistentIndex{index: index}
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}
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type fakeConsistentIndex struct {
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index uint64
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term uint64
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}
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func (f *fakeConsistentIndex) ConsistentIndex() uint64 { return f.index }
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func (f *fakeConsistentIndex) SetConsistentIndex(index uint64, term uint64) {
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atomic.StoreUint64(&f.index, index)
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atomic.StoreUint64(&f.term, term)
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}
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func (f *fakeConsistentIndex) UnsafeSave(_ backend.BatchTx) {}
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func (f *fakeConsistentIndex) SetBackend(_ Backend) {}
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func UpdateConsistentIndex(tx backend.BatchTx, index uint64, term uint64, onlyGrow bool) {
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tx.Lock()
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defer tx.Unlock()
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schema.UnsafeUpdateConsistentIndex(tx, index, term, onlyGrow)
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}
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