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144 lines
4.4 KiB
144 lines
4.4 KiB
![]()
5 years ago
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/*
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* MinIO Cloud Storage, (C) 2019 MinIO, Inc.
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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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*/
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package cmd
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import (
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"reflect"
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"sync"
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"time"
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)
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const (
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globalMergeLookupTimeout = time.Minute * 1 // 1 minutes.
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)
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// mergeWalk - represents the go routine that does the merge walk.
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type mergeWalk struct {
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entryChs []FileInfoCh
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endWalkCh chan struct{} // To signal when mergeWalk go-routine should end.
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endTimerCh chan<- struct{} // To signal when timer go-routine should end.
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}
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// MergeWalkPool - pool of mergeWalk go routines.
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// A mergeWalk is added to the pool by Set() and removed either by
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// doing a Release() or if the concerned timer goes off.
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// mergeWalkPool's purpose is to maintain active mergeWalk go-routines in a map so that
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// it can be looked up across related list calls.
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type MergeWalkPool struct {
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pool map[listParams][]mergeWalk
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timeOut time.Duration
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lock *sync.Mutex
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}
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// NewMergeWalkPool - initialize new tree walk pool.
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func NewMergeWalkPool(timeout time.Duration) *MergeWalkPool {
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tPool := &MergeWalkPool{
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pool: make(map[listParams][]mergeWalk),
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timeOut: timeout,
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lock: &sync.Mutex{},
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}
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return tPool
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}
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// Release - selects a mergeWalk from the pool based on the input
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// listParams, removes it from the pool, and returns the MergeWalkResult
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// channel.
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// Returns nil if listParams does not have an asccociated mergeWalk.
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func (t MergeWalkPool) Release(params listParams) ([]FileInfoCh, chan struct{}) {
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t.lock.Lock()
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defer t.lock.Unlock()
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walks, ok := t.pool[params] // Pick the valid walks.
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if ok {
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if len(walks) > 0 {
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// Pop out the first valid walk entry.
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walk := walks[0]
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walks = walks[1:]
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if len(walks) > 0 {
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t.pool[params] = walks
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} else {
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delete(t.pool, params)
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}
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walk.endTimerCh <- struct{}{}
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return walk.entryChs, walk.endWalkCh
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}
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}
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// Release return nil if params not found.
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return nil, nil
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}
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// Set - adds a mergeWalk to the mergeWalkPool.
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// Also starts a timer go-routine that ends when:
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// 1) time.After() expires after t.timeOut seconds.
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// The expiration is needed so that the mergeWalk go-routine resources are freed after a timeout
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// if the S3 client does only partial listing of objects.
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// 2) Relase() signals the timer go-routine to end on endTimerCh.
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// During listing the timer should not timeout and end the mergeWalk go-routine, hence the
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// timer go-routine should be ended.
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func (t MergeWalkPool) Set(params listParams, resultChs []FileInfoCh, endWalkCh chan struct{}) {
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t.lock.Lock()
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defer t.lock.Unlock()
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// Should be a buffered channel so that Release() never blocks.
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endTimerCh := make(chan struct{}, 1)
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walkInfo := mergeWalk{
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entryChs: resultChs,
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endWalkCh: endWalkCh,
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endTimerCh: endTimerCh,
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}
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// Append new walk info.
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t.pool[params] = append(t.pool[params], walkInfo)
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// Timer go-routine which times out after t.timeOut seconds.
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go func(endTimerCh <-chan struct{}, walkInfo mergeWalk) {
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select {
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// Wait until timeOut
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case <-time.After(t.timeOut):
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// Timeout has expired. Remove the mergeWalk from mergeWalkPool and
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// end the mergeWalk go-routine.
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t.lock.Lock()
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walks, ok := t.pool[params]
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if ok {
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// Trick of filtering without allocating
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// https://github.com/golang/go/wiki/SliceTricks#filtering-without-allocating
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nwalks := walks[:0]
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// Look for walkInfo, remove it from the walks list.
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for _, walk := range walks {
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if !reflect.DeepEqual(walk, walkInfo) {
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nwalks = append(nwalks, walk)
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}
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}
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if len(nwalks) == 0 {
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// No more mergeWalk go-routines associated with listParams
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// hence remove map entry.
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delete(t.pool, params)
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} else {
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// There are more mergeWalk go-routines associated with listParams
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// hence save the list in the map.
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t.pool[params] = nwalks
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}
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}
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// Signal the mergeWalk go-routine to die.
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close(endWalkCh)
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t.lock.Unlock()
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case <-endTimerCh:
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return
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}
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}(endTimerCh, walkInfo)
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}
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