mirror of
https://github.com/go-gitea/gitea
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464 lines
11 KiB
Go
464 lines
11 KiB
Go
// Copyright (c) 2012, Suryandaru Triandana <syndtr@gmail.com>
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// All rights reserved.
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//
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// Use of this source code is governed by a BSD-style license that can be
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// found in the LICENSE file.
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package leveldb
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import (
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"sync/atomic"
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"time"
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"github.com/syndtr/goleveldb/leveldb/memdb"
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"github.com/syndtr/goleveldb/leveldb/opt"
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"github.com/syndtr/goleveldb/leveldb/util"
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)
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func (db *DB) writeJournal(batches []*Batch, seq uint64, sync bool) error {
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wr, err := db.journal.Next()
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if err != nil {
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return err
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}
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if err := writeBatchesWithHeader(wr, batches, seq); err != nil {
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return err
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}
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if err := db.journal.Flush(); err != nil {
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return err
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}
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if sync {
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return db.journalWriter.Sync()
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}
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return nil
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}
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func (db *DB) rotateMem(n int, wait bool) (mem *memDB, err error) {
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retryLimit := 3
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retry:
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// Wait for pending memdb compaction.
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err = db.compTriggerWait(db.mcompCmdC)
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if err != nil {
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return
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}
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retryLimit--
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// Create new memdb and journal.
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mem, err = db.newMem(n)
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if err != nil {
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if err == errHasFrozenMem {
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if retryLimit <= 0 {
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panic("BUG: still has frozen memdb")
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}
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goto retry
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}
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return
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}
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// Schedule memdb compaction.
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if wait {
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err = db.compTriggerWait(db.mcompCmdC)
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} else {
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db.compTrigger(db.mcompCmdC)
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}
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return
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}
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func (db *DB) flush(n int) (mdb *memDB, mdbFree int, err error) {
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delayed := false
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slowdownTrigger := db.s.o.GetWriteL0SlowdownTrigger()
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pauseTrigger := db.s.o.GetWriteL0PauseTrigger()
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flush := func() (retry bool) {
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mdb = db.getEffectiveMem()
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if mdb == nil {
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err = ErrClosed
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return false
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}
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defer func() {
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if retry {
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mdb.decref()
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mdb = nil
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}
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}()
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tLen := db.s.tLen(0)
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mdbFree = mdb.Free()
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switch {
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case tLen >= slowdownTrigger && !delayed:
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delayed = true
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time.Sleep(time.Millisecond)
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case mdbFree >= n:
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return false
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case tLen >= pauseTrigger:
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delayed = true
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// Set the write paused flag explicitly.
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atomic.StoreInt32(&db.inWritePaused, 1)
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err = db.compTriggerWait(db.tcompCmdC)
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// Unset the write paused flag.
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atomic.StoreInt32(&db.inWritePaused, 0)
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if err != nil {
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return false
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}
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default:
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// Allow memdb to grow if it has no entry.
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if mdb.Len() == 0 {
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mdbFree = n
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} else {
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mdb.decref()
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mdb, err = db.rotateMem(n, false)
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if err == nil {
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mdbFree = mdb.Free()
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} else {
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mdbFree = 0
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}
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}
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return false
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}
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return true
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}
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start := time.Now()
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for flush() {
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}
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if delayed {
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db.writeDelay += time.Since(start)
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db.writeDelayN++
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} else if db.writeDelayN > 0 {
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db.logf("db@write was delayed N·%d T·%v", db.writeDelayN, db.writeDelay)
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atomic.AddInt32(&db.cWriteDelayN, int32(db.writeDelayN))
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atomic.AddInt64(&db.cWriteDelay, int64(db.writeDelay))
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db.writeDelay = 0
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db.writeDelayN = 0
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}
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return
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}
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type writeMerge struct {
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sync bool
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batch *Batch
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keyType keyType
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key, value []byte
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}
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func (db *DB) unlockWrite(overflow bool, merged int, err error) {
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for i := 0; i < merged; i++ {
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db.writeAckC <- err
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}
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if overflow {
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// Pass lock to the next write (that failed to merge).
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db.writeMergedC <- false
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} else {
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// Release lock.
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<-db.writeLockC
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}
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}
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// ourBatch is batch that we can modify.
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func (db *DB) writeLocked(batch, ourBatch *Batch, merge, sync bool) error {
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// Try to flush memdb. This method would also trying to throttle writes
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// if it is too fast and compaction cannot catch-up.
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mdb, mdbFree, err := db.flush(batch.internalLen)
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if err != nil {
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db.unlockWrite(false, 0, err)
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return err
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}
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defer mdb.decref()
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var (
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overflow bool
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merged int
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batches = []*Batch{batch}
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)
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if merge {
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// Merge limit.
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var mergeLimit int
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if batch.internalLen > 128<<10 {
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mergeLimit = (1 << 20) - batch.internalLen
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} else {
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mergeLimit = 128 << 10
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}
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mergeCap := mdbFree - batch.internalLen
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if mergeLimit > mergeCap {
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mergeLimit = mergeCap
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}
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merge:
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for mergeLimit > 0 {
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select {
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case incoming := <-db.writeMergeC:
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if incoming.batch != nil {
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// Merge batch.
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if incoming.batch.internalLen > mergeLimit {
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overflow = true
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break merge
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}
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batches = append(batches, incoming.batch)
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mergeLimit -= incoming.batch.internalLen
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} else {
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// Merge put.
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internalLen := len(incoming.key) + len(incoming.value) + 8
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if internalLen > mergeLimit {
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overflow = true
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break merge
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}
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if ourBatch == nil {
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ourBatch = db.batchPool.Get().(*Batch)
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ourBatch.Reset()
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batches = append(batches, ourBatch)
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}
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// We can use same batch since concurrent write doesn't
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// guarantee write order.
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ourBatch.appendRec(incoming.keyType, incoming.key, incoming.value)
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mergeLimit -= internalLen
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}
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sync = sync || incoming.sync
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merged++
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db.writeMergedC <- true
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default:
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break merge
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}
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}
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}
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// Release ourBatch if any.
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if ourBatch != nil {
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defer db.batchPool.Put(ourBatch)
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}
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// Seq number.
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seq := db.seq + 1
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// Write journal.
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if err := db.writeJournal(batches, seq, sync); err != nil {
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db.unlockWrite(overflow, merged, err)
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return err
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}
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// Put batches.
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for _, batch := range batches {
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if err := batch.putMem(seq, mdb.DB); err != nil {
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panic(err)
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}
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seq += uint64(batch.Len())
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}
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// Incr seq number.
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db.addSeq(uint64(batchesLen(batches)))
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// Rotate memdb if it's reach the threshold.
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if batch.internalLen >= mdbFree {
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db.rotateMem(0, false)
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}
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db.unlockWrite(overflow, merged, nil)
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return nil
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}
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// Write apply the given batch to the DB. The batch records will be applied
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// sequentially. Write might be used concurrently, when used concurrently and
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// batch is small enough, write will try to merge the batches. Set NoWriteMerge
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// option to true to disable write merge.
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//
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// It is safe to modify the contents of the arguments after Write returns but
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// not before. Write will not modify content of the batch.
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func (db *DB) Write(batch *Batch, wo *opt.WriteOptions) error {
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if err := db.ok(); err != nil || batch == nil || batch.Len() == 0 {
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return err
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}
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// If the batch size is larger than write buffer, it may justified to write
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// using transaction instead. Using transaction the batch will be written
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// into tables directly, skipping the journaling.
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if batch.internalLen > db.s.o.GetWriteBuffer() && !db.s.o.GetDisableLargeBatchTransaction() {
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tr, err := db.OpenTransaction()
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if err != nil {
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return err
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}
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if err := tr.Write(batch, wo); err != nil {
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tr.Discard()
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return err
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}
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return tr.Commit()
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}
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merge := !wo.GetNoWriteMerge() && !db.s.o.GetNoWriteMerge()
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sync := wo.GetSync() && !db.s.o.GetNoSync()
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// Acquire write lock.
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if merge {
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select {
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case db.writeMergeC <- writeMerge{sync: sync, batch: batch}:
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if <-db.writeMergedC {
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// Write is merged.
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return <-db.writeAckC
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}
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// Write is not merged, the write lock is handed to us. Continue.
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case db.writeLockC <- struct{}{}:
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// Write lock acquired.
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case err := <-db.compPerErrC:
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// Compaction error.
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return err
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case <-db.closeC:
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// Closed
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return ErrClosed
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}
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} else {
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select {
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case db.writeLockC <- struct{}{}:
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// Write lock acquired.
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case err := <-db.compPerErrC:
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// Compaction error.
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return err
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case <-db.closeC:
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// Closed
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return ErrClosed
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}
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}
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return db.writeLocked(batch, nil, merge, sync)
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}
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func (db *DB) putRec(kt keyType, key, value []byte, wo *opt.WriteOptions) error {
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if err := db.ok(); err != nil {
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return err
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}
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merge := !wo.GetNoWriteMerge() && !db.s.o.GetNoWriteMerge()
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sync := wo.GetSync() && !db.s.o.GetNoSync()
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// Acquire write lock.
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if merge {
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select {
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case db.writeMergeC <- writeMerge{sync: sync, keyType: kt, key: key, value: value}:
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if <-db.writeMergedC {
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// Write is merged.
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return <-db.writeAckC
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}
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// Write is not merged, the write lock is handed to us. Continue.
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case db.writeLockC <- struct{}{}:
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// Write lock acquired.
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case err := <-db.compPerErrC:
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// Compaction error.
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return err
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case <-db.closeC:
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// Closed
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return ErrClosed
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}
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} else {
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select {
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case db.writeLockC <- struct{}{}:
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// Write lock acquired.
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case err := <-db.compPerErrC:
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// Compaction error.
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return err
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case <-db.closeC:
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// Closed
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return ErrClosed
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}
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}
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batch := db.batchPool.Get().(*Batch)
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batch.Reset()
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batch.appendRec(kt, key, value)
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return db.writeLocked(batch, batch, merge, sync)
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}
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// Put sets the value for the given key. It overwrites any previous value
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// for that key; a DB is not a multi-map. Write merge also applies for Put, see
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// Write.
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//
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// It is safe to modify the contents of the arguments after Put returns but not
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// before.
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func (db *DB) Put(key, value []byte, wo *opt.WriteOptions) error {
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return db.putRec(keyTypeVal, key, value, wo)
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}
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// Delete deletes the value for the given key. Delete will not returns error if
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// key doesn't exist. Write merge also applies for Delete, see Write.
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//
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// It is safe to modify the contents of the arguments after Delete returns but
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// not before.
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func (db *DB) Delete(key []byte, wo *opt.WriteOptions) error {
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return db.putRec(keyTypeDel, key, nil, wo)
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}
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func isMemOverlaps(icmp *iComparer, mem *memdb.DB, min, max []byte) bool {
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iter := mem.NewIterator(nil)
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defer iter.Release()
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return (max == nil || (iter.First() && icmp.uCompare(max, internalKey(iter.Key()).ukey()) >= 0)) &&
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(min == nil || (iter.Last() && icmp.uCompare(min, internalKey(iter.Key()).ukey()) <= 0))
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}
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// CompactRange compacts the underlying DB for the given key range.
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// In particular, deleted and overwritten versions are discarded,
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// and the data is rearranged to reduce the cost of operations
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// needed to access the data. This operation should typically only
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// be invoked by users who understand the underlying implementation.
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//
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// A nil Range.Start is treated as a key before all keys in the DB.
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// And a nil Range.Limit is treated as a key after all keys in the DB.
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// Therefore if both is nil then it will compact entire DB.
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func (db *DB) CompactRange(r util.Range) error {
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if err := db.ok(); err != nil {
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return err
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}
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// Lock writer.
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select {
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case db.writeLockC <- struct{}{}:
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case err := <-db.compPerErrC:
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return err
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case <-db.closeC:
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return ErrClosed
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}
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// Check for overlaps in memdb.
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mdb := db.getEffectiveMem()
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if mdb == nil {
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return ErrClosed
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}
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defer mdb.decref()
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if isMemOverlaps(db.s.icmp, mdb.DB, r.Start, r.Limit) {
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// Memdb compaction.
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if _, err := db.rotateMem(0, false); err != nil {
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<-db.writeLockC
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return err
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}
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<-db.writeLockC
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if err := db.compTriggerWait(db.mcompCmdC); err != nil {
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return err
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}
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} else {
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<-db.writeLockC
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}
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// Table compaction.
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return db.compTriggerRange(db.tcompCmdC, -1, r.Start, r.Limit)
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}
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// SetReadOnly makes DB read-only. It will stay read-only until reopened.
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func (db *DB) SetReadOnly() error {
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if err := db.ok(); err != nil {
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return err
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}
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// Lock writer.
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select {
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case db.writeLockC <- struct{}{}:
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db.compWriteLocking = true
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case err := <-db.compPerErrC:
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return err
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case <-db.closeC:
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return ErrClosed
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}
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// Set compaction read-only.
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select {
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case db.compErrSetC <- ErrReadOnly:
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case perr := <-db.compPerErrC:
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return perr
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case <-db.closeC:
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return ErrClosed
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}
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return nil
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}
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