379 lines
10 KiB
Go
379 lines
10 KiB
Go
// Copyright 2019 The go-ethereum Authors
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// This file is part of the go-ethereum library.
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//
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// The go-ethereum library is free software: you can redistribute it and/or modify
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// it under the terms of the GNU Lesser General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// The go-ethereum library is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU Lesser General Public License for more details.
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//
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// You should have received a copy of the GNU Lesser General Public License
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// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.
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package les
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import (
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"sort"
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"sync"
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"sync/atomic"
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"github.com/ethereum/go-ethereum/common/mclock"
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"github.com/ethereum/go-ethereum/common/prque"
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)
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// servingQueue allows running tasks in a limited number of threads and puts the
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// waiting tasks in a priority queue
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type servingQueue struct {
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recentTime, queuedTime, servingTimeDiff uint64
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burstLimit, burstDropLimit uint64
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burstDecRate float64
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lastUpdate mclock.AbsTime
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queueAddCh, queueBestCh chan *servingTask
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stopThreadCh, quit chan struct{}
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setThreadsCh chan int
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wg sync.WaitGroup
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threadCount int // number of currently running threads
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queue *prque.Prque // priority queue for waiting or suspended tasks
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best *servingTask // the highest priority task (not included in the queue)
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suspendBias int64 // priority bias against suspending an already running task
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}
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// servingTask represents a request serving task. Tasks can be implemented to
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// run in multiple steps, allowing the serving queue to suspend execution between
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// steps if higher priority tasks are entered. The creator of the task should
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// set the following fields:
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//
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// - priority: greater value means higher priority; values can wrap around the int64 range
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// - run: execute a single step; return true if finished
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// - after: executed after run finishes or returns an error, receives the total serving time
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type servingTask struct {
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sq *servingQueue
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servingTime, timeAdded, maxTime, expTime uint64
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peer *peer
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priority int64
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biasAdded bool
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token runToken
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tokenCh chan runToken
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}
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// runToken received by servingTask.start allows the task to run. Closing the
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// channel by servingTask.stop signals the thread controller to allow a new task
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// to start running.
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type runToken chan struct{}
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// start blocks until the task can start and returns true if it is allowed to run.
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// Returning false means that the task should be cancelled.
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func (t *servingTask) start() bool {
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if t.peer.isFrozen() {
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return false
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}
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t.tokenCh = make(chan runToken, 1)
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select {
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case t.sq.queueAddCh <- t:
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case <-t.sq.quit:
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return false
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}
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select {
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case t.token = <-t.tokenCh:
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case <-t.sq.quit:
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return false
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}
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if t.token == nil {
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return false
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}
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t.servingTime -= uint64(mclock.Now())
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return true
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}
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// done signals the thread controller about the task being finished and returns
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// the total serving time of the task in nanoseconds.
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func (t *servingTask) done() uint64 {
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t.servingTime += uint64(mclock.Now())
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close(t.token)
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diff := t.servingTime - t.timeAdded
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t.timeAdded = t.servingTime
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if t.expTime > diff {
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t.expTime -= diff
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atomic.AddUint64(&t.sq.servingTimeDiff, t.expTime)
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} else {
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t.expTime = 0
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}
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return t.servingTime
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}
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// waitOrStop can be called during the execution of the task. It blocks if there
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// is a higher priority task waiting (a bias is applied in favor of the currently
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// running task). Returning true means that the execution can be resumed. False
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// means the task should be cancelled.
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func (t *servingTask) waitOrStop() bool {
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t.done()
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if !t.biasAdded {
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t.priority += t.sq.suspendBias
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t.biasAdded = true
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}
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return t.start()
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}
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// newServingQueue returns a new servingQueue
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func newServingQueue(suspendBias int64, utilTarget float64) *servingQueue {
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sq := &servingQueue{
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queue: prque.New(nil),
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suspendBias: suspendBias,
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queueAddCh: make(chan *servingTask, 100),
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queueBestCh: make(chan *servingTask),
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stopThreadCh: make(chan struct{}),
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quit: make(chan struct{}),
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setThreadsCh: make(chan int, 10),
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burstLimit: uint64(utilTarget * bufLimitRatio * 1200000),
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burstDropLimit: uint64(utilTarget * bufLimitRatio * 1000000),
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burstDecRate: utilTarget,
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lastUpdate: mclock.Now(),
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}
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sq.wg.Add(2)
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go sq.queueLoop()
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go sq.threadCountLoop()
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return sq
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}
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// newTask creates a new task with the given priority
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func (sq *servingQueue) newTask(peer *peer, maxTime uint64, priority int64) *servingTask {
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return &servingTask{
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sq: sq,
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peer: peer,
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maxTime: maxTime,
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expTime: maxTime,
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priority: priority,
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}
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}
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// threadController is started in multiple goroutines and controls the execution
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// of tasks. The number of active thread controllers equals the allowed number of
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// concurrently running threads. It tries to fetch the highest priority queued
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// task first. If there are no queued tasks waiting then it can directly catch
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// run tokens from the token channel and allow the corresponding tasks to run
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// without entering the priority queue.
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func (sq *servingQueue) threadController() {
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for {
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token := make(runToken)
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select {
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case best := <-sq.queueBestCh:
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best.tokenCh <- token
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case <-sq.stopThreadCh:
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sq.wg.Done()
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return
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case <-sq.quit:
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sq.wg.Done()
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return
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}
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<-token
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select {
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case <-sq.stopThreadCh:
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sq.wg.Done()
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return
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case <-sq.quit:
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sq.wg.Done()
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return
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default:
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}
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}
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}
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type (
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// peerTasks lists the tasks received from a given peer when selecting peers to freeze
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peerTasks struct {
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peer *peer
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list []*servingTask
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sumTime uint64
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priority float64
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}
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// peerList is a sortable list of peerTasks
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peerList []*peerTasks
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)
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func (l peerList) Len() int {
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return len(l)
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}
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func (l peerList) Less(i, j int) bool {
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return l[i].priority < l[j].priority
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}
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func (l peerList) Swap(i, j int) {
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l[i], l[j] = l[j], l[i]
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}
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// freezePeers selects the peers with the worst priority queued tasks and freezes
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// them until burstTime goes under burstDropLimit or all peers are frozen
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func (sq *servingQueue) freezePeers() {
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peerMap := make(map[*peer]*peerTasks)
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var peerList peerList
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if sq.best != nil {
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sq.queue.Push(sq.best, sq.best.priority)
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}
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sq.best = nil
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for sq.queue.Size() > 0 {
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task := sq.queue.PopItem().(*servingTask)
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tasks := peerMap[task.peer]
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if tasks == nil {
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bufValue, bufLimit := task.peer.fcClient.BufferStatus()
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if bufLimit < 1 {
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bufLimit = 1
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}
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tasks = &peerTasks{
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peer: task.peer,
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priority: float64(bufValue) / float64(bufLimit), // lower value comes first
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}
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peerMap[task.peer] = tasks
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peerList = append(peerList, tasks)
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}
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tasks.list = append(tasks.list, task)
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tasks.sumTime += task.expTime
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}
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sort.Sort(peerList)
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drop := true
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for _, tasks := range peerList {
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if drop {
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tasks.peer.freezeClient()
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tasks.peer.fcClient.Freeze()
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sq.queuedTime -= tasks.sumTime
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sqQueuedGauge.Update(int64(sq.queuedTime))
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clientFreezeMeter.Mark(1)
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drop = sq.recentTime+sq.queuedTime > sq.burstDropLimit
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for _, task := range tasks.list {
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task.tokenCh <- nil
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}
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} else {
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for _, task := range tasks.list {
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sq.queue.Push(task, task.priority)
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}
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}
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}
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if sq.queue.Size() > 0 {
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sq.best = sq.queue.PopItem().(*servingTask)
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}
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}
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// updateRecentTime recalculates the recent serving time value
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func (sq *servingQueue) updateRecentTime() {
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subTime := atomic.SwapUint64(&sq.servingTimeDiff, 0)
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now := mclock.Now()
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dt := now - sq.lastUpdate
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sq.lastUpdate = now
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if dt > 0 {
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subTime += uint64(float64(dt) * sq.burstDecRate)
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}
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if sq.recentTime > subTime {
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sq.recentTime -= subTime
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} else {
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sq.recentTime = 0
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}
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}
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// addTask inserts a task into the priority queue
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func (sq *servingQueue) addTask(task *servingTask) {
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if sq.best == nil {
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sq.best = task
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} else if task.priority > sq.best.priority {
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sq.queue.Push(sq.best, sq.best.priority)
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sq.best = task
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} else {
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sq.queue.Push(task, task.priority)
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}
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sq.updateRecentTime()
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sq.queuedTime += task.expTime
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sqServedGauge.Update(int64(sq.recentTime))
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sqQueuedGauge.Update(int64(sq.queuedTime))
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if sq.recentTime+sq.queuedTime > sq.burstLimit {
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sq.freezePeers()
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}
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}
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// queueLoop is an event loop running in a goroutine. It receives tasks from queueAddCh
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// and always tries to send the highest priority task to queueBestCh. Successfully sent
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// tasks are removed from the queue.
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func (sq *servingQueue) queueLoop() {
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for {
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if sq.best != nil {
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expTime := sq.best.expTime
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select {
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case task := <-sq.queueAddCh:
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sq.addTask(task)
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case sq.queueBestCh <- sq.best:
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sq.updateRecentTime()
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sq.queuedTime -= expTime
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sq.recentTime += expTime
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sqServedGauge.Update(int64(sq.recentTime))
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sqQueuedGauge.Update(int64(sq.queuedTime))
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if sq.queue.Size() == 0 {
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sq.best = nil
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} else {
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sq.best, _ = sq.queue.PopItem().(*servingTask)
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}
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case <-sq.quit:
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sq.wg.Done()
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return
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}
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} else {
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select {
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case task := <-sq.queueAddCh:
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sq.addTask(task)
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case <-sq.quit:
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sq.wg.Done()
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return
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}
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}
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}
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}
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// threadCountLoop is an event loop running in a goroutine. It adjusts the number
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// of active thread controller goroutines.
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func (sq *servingQueue) threadCountLoop() {
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var threadCountTarget int
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for {
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for threadCountTarget > sq.threadCount {
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sq.wg.Add(1)
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go sq.threadController()
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sq.threadCount++
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}
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if threadCountTarget < sq.threadCount {
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select {
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case threadCountTarget = <-sq.setThreadsCh:
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case sq.stopThreadCh <- struct{}{}:
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sq.threadCount--
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case <-sq.quit:
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sq.wg.Done()
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return
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}
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} else {
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select {
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case threadCountTarget = <-sq.setThreadsCh:
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case <-sq.quit:
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sq.wg.Done()
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return
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}
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}
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}
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}
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// setThreads sets the allowed processing thread count, suspending tasks as soon as
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// possible if necessary.
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func (sq *servingQueue) setThreads(threadCount int) {
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select {
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case sq.setThreadsCh <- threadCount:
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case <-sq.quit:
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return
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}
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}
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// stop stops task processing as soon as possible and shuts down the serving queue.
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func (sq *servingQueue) stop() {
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close(sq.quit)
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sq.wg.Wait()
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}
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