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log.go
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log.go
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// Copyright 2019-present Open Networking Foundation.
//
// 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 log
import (
raft "github.com/atomix/raft-replica/pkg/atomix/raft/protocol"
"io"
)
// NewMemoryLog creates a new in-memory Log
func NewMemoryLog() Log {
log := &memoryLog{
entries: make([]*Entry, 0, 1024),
firstIndex: 1,
readers: make([]*memoryReader, 0, 10),
}
log.writer = &memoryWriter{
log: log,
}
return log
}
// Log provides for reading and writing entries in the Raft log
type Log interface {
io.Closer
// Writer returns the Raft log writer
Writer() Writer
// OpenReader opens a Raft log reader
OpenReader(index raft.Index) Reader
}
// Writer supports writing entries to the Raft log
type Writer interface {
io.Closer
// LastIndex returns the last index written to the log
LastIndex() raft.Index
// LastEntry returns the last entry written to the log
LastEntry() *Entry
// Append appends the given entry to the log
Append(entry *raft.LogEntry) *Entry
// Reset resets the log writer to the given index
Reset(index raft.Index)
// Truncate truncates the tail of the log to the given index
Truncate(index raft.Index)
}
// Reader supports reading of entries from the Raft log
type Reader interface {
io.Closer
// FirstIndex returns the first index in the log
FirstIndex() raft.Index
// LastIndex returns the last index in the log
LastIndex() raft.Index
// CurrentIndex returns the current index of the reader
CurrentIndex() raft.Index
// CurrentEntry returns the current Entry
CurrentEntry() *Entry
// NextIndex returns the next index in the log
NextIndex() raft.Index
// NextEntry advances the log index and returns the next entry in the log
NextEntry() *Entry
// Reset resets the log reader to the given index
Reset(index raft.Index)
}
// Entry is an indexed Raft log entry
type Entry struct {
Index raft.Index
Entry *raft.LogEntry
}
type memoryLog struct {
entries []*Entry
firstIndex raft.Index
writer *memoryWriter
readers []*memoryReader
}
func (l *memoryLog) Writer() Writer {
return l.writer
}
func (l *memoryLog) OpenReader(index raft.Index) Reader {
readerIndex := -1
for i := 0; i < len(l.entries); i++ {
if l.entries[i].Index == index {
readerIndex = i - 1
break
}
}
reader := &memoryReader{
log: l,
index: readerIndex,
}
l.readers = append(l.readers, reader)
return reader
}
func (l *memoryLog) Close() error {
return nil
}
type memoryWriter struct {
log *memoryLog
}
func (w *memoryWriter) LastIndex() raft.Index {
if entry := w.LastEntry(); entry != nil {
return entry.Index
}
return w.log.firstIndex - 1
}
func (w *memoryWriter) LastEntry() *Entry {
if len(w.log.entries) == 0 {
return nil
}
return w.log.entries[len(w.log.entries)-1]
}
func (w *memoryWriter) nextIndex() raft.Index {
if len(w.log.entries) == 0 {
return w.log.firstIndex
}
return w.log.entries[len(w.log.entries)-1].Index + 1
}
func (w *memoryWriter) Append(entry *raft.LogEntry) *Entry {
indexed := &Entry{
Index: w.nextIndex(),
Entry: entry,
}
w.log.entries = append(w.log.entries, indexed)
return indexed
}
func (w *memoryWriter) Reset(index raft.Index) {
w.log.entries = w.log.entries[:0]
w.log.firstIndex = index
for _, reader := range w.log.readers {
reader.maybeReset()
}
}
func (w *memoryWriter) Truncate(index raft.Index) {
for i := 0; i < len(w.log.entries); i++ {
if w.log.entries[i].Index > index {
w.log.entries = w.log.entries[:i]
break
}
}
for _, reader := range w.log.readers {
reader.maybeReset()
}
}
func (w *memoryWriter) Close() error {
panic("implement me")
}
type memoryReader struct {
log *memoryLog
index int
}
func (r *memoryReader) FirstIndex() raft.Index {
return r.log.firstIndex
}
func (r *memoryReader) LastIndex() raft.Index {
if len(r.log.entries) == 0 {
return r.log.firstIndex - 1
}
return r.log.entries[len(r.log.entries)-1].Index
}
func (r *memoryReader) CurrentIndex() raft.Index {
if r.index == -1 || len(r.log.entries) == 0 {
return r.log.firstIndex - 1
}
return r.log.entries[r.index].Index
}
func (r *memoryReader) CurrentEntry() *Entry {
if r.index == -1 || len(r.log.entries) == 0 {
return nil
}
return r.log.entries[r.index]
}
func (r *memoryReader) NextIndex() raft.Index {
if r.index == -1 || len(r.log.entries) == 0 {
return r.log.firstIndex
}
return r.log.entries[r.index].Index + 1
}
func (r *memoryReader) NextEntry() *Entry {
if len(r.log.entries) > r.index+1 {
r.index++
return r.log.entries[r.index]
}
return nil
}
func (r *memoryReader) Reset(index raft.Index) {
for i := 0; i < len(r.log.entries); i++ {
if r.log.entries[i].Index >= index {
r.index = i - 1
break
}
}
}
func (r *memoryReader) maybeReset() {
if r.index >= 0 && len(r.log.entries) <= r.index {
r.index = len(r.log.entries) - 1
}
}
func (r *memoryReader) Close() error {
return nil
}