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215 lines
5.5 KiB
Go
215 lines
5.5 KiB
Go
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// Copyright 2012, Google Inc. All rights reserved.
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// Use of this source code is governed by a BSD-style
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// license that can be found in the LICENSE file.
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package pools
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import (
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"fmt"
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"sync"
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"time"
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)
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// RoundRobin is deprecated. Use ResourcePool instead.
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// RoundRobin allows you to use a pool of resources in a round robin fashion.
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type RoundRobin struct {
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mu sync.Mutex
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available *sync.Cond
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resources chan fifoWrapper
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size int64
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factory Factory
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idleTimeout time.Duration
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// stats
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waitCount int64
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waitTime time.Duration
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}
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type fifoWrapper struct {
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resource Resource
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timeUsed time.Time
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}
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// NewRoundRobin creates a new RoundRobin pool.
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// capacity is the maximum number of resources RoundRobin will create.
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// factory will be the function used to create resources.
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// If a resource is unused beyond idleTimeout, it's discarded.
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func NewRoundRobin(capacity int, idleTimeout time.Duration) *RoundRobin {
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r := &RoundRobin{
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resources: make(chan fifoWrapper, capacity),
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size: 0,
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idleTimeout: idleTimeout,
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}
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r.available = sync.NewCond(&r.mu)
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return r
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}
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// Open starts allowing the creation of resources
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func (rr *RoundRobin) Open(factory Factory) {
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rr.mu.Lock()
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defer rr.mu.Unlock()
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rr.factory = factory
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}
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// Close empties the pool calling Close on all its resources.
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// It waits for all resources to be returned (Put).
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func (rr *RoundRobin) Close() {
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rr.mu.Lock()
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defer rr.mu.Unlock()
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for rr.size > 0 {
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select {
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case fw := <-rr.resources:
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go fw.resource.Close()
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rr.size--
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default:
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rr.available.Wait()
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}
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}
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rr.factory = nil
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}
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func (rr *RoundRobin) IsClosed() bool {
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return rr.factory == nil
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}
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// Get will return the next available resource. If none is available, and capacity
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// has not been reached, it will create a new one using the factory. Otherwise,
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// it will indefinitely wait till the next resource becomes available.
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func (rr *RoundRobin) Get() (resource Resource, err error) {
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return rr.get(true)
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}
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// TryGet will return the next available resource. If none is available, and capacity
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// has not been reached, it will create a new one using the factory. Otherwise,
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// it will return nil with no error.
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func (rr *RoundRobin) TryGet() (resource Resource, err error) {
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return rr.get(false)
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}
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func (rr *RoundRobin) get(wait bool) (resource Resource, err error) {
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rr.mu.Lock()
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defer rr.mu.Unlock()
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// Any waits in this loop will release the lock, and it will be
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// reacquired before the waits return.
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for {
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select {
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case fw := <-rr.resources:
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// Found a free resource in the channel
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if rr.idleTimeout > 0 && fw.timeUsed.Add(rr.idleTimeout).Sub(time.Now()) < 0 {
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// resource has been idle for too long. Discard & go for next.
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go fw.resource.Close()
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rr.size--
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// Nobody else should be waiting, but signal anyway.
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rr.available.Signal()
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continue
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}
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return fw.resource, nil
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default:
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// resource channel is empty
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if rr.size >= int64(cap(rr.resources)) {
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// The pool is full
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if wait {
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start := time.Now()
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rr.available.Wait()
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rr.recordWait(start)
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continue
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}
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return nil, nil
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}
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// Pool is not full. Create a resource.
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if resource, err = rr.waitForCreate(); err != nil {
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// size was decremented, and somebody could be waiting.
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rr.available.Signal()
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return nil, err
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}
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// Creation successful. Account for this by incrementing size.
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rr.size++
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return resource, err
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}
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}
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}
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func (rr *RoundRobin) recordWait(start time.Time) {
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rr.waitCount++
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rr.waitTime += time.Now().Sub(start)
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}
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func (rr *RoundRobin) waitForCreate() (resource Resource, err error) {
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// Prevent thundering herd: increment size before creating resource, and decrement after.
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rr.size++
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rr.mu.Unlock()
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defer func() {
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rr.mu.Lock()
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rr.size--
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}()
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return rr.factory()
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}
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// Put will return a resource to the pool. You MUST return every resource to the pool,
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// even if it's closed. If a resource is closed, you should call Put(nil).
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func (rr *RoundRobin) Put(resource Resource) {
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rr.mu.Lock()
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defer rr.available.Signal()
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defer rr.mu.Unlock()
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if rr.size > int64(cap(rr.resources)) {
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if resource != nil {
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go resource.Close()
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}
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rr.size--
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} else if resource == nil {
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rr.size--
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} else {
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if len(rr.resources) == cap(rr.resources) {
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panic("unexpected")
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}
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rr.resources <- fifoWrapper{resource, time.Now()}
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}
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}
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// Set capacity changes the capacity of the pool.
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// You can use it to expand or shrink.
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func (rr *RoundRobin) SetCapacity(capacity int) error {
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rr.mu.Lock()
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defer rr.available.Broadcast()
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defer rr.mu.Unlock()
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nr := make(chan fifoWrapper, capacity)
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// This loop transfers resources from the old channel
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// to the new one, until it fills up or runs out.
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// It discards extras, if any.
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for {
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select {
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case fw := <-rr.resources:
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if len(nr) < cap(nr) {
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nr <- fw
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} else {
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go fw.resource.Close()
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rr.size--
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}
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continue
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default:
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}
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break
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}
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rr.resources = nr
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return nil
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}
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func (rr *RoundRobin) SetIdleTimeout(idleTimeout time.Duration) {
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rr.mu.Lock()
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defer rr.mu.Unlock()
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rr.idleTimeout = idleTimeout
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}
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func (rr *RoundRobin) StatsJSON() string {
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s, c, a, wc, wt, it := rr.Stats()
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return fmt.Sprintf("{\"Size\": %v, \"Capacity\": %v, \"Available\": %v, \"WaitCount\": %v, \"WaitTime\": %v, \"IdleTimeout\": %v}", s, c, a, wc, int64(wt), int64(it))
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}
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func (rr *RoundRobin) Stats() (size, capacity, available, waitCount int64, waitTime, idleTimeout time.Duration) {
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rr.mu.Lock()
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defer rr.mu.Unlock()
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return rr.size, int64(cap(rr.resources)), int64(len(rr.resources)), rr.waitCount, rr.waitTime, rr.idleTimeout
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}
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