mirror of
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229 lines
6.1 KiB
Go
229 lines
6.1 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 provides functionality to manage and reuse resources
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// like connections.
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package pools
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import (
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"fmt"
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"time"
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"github.com/ngaut/sync2"
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)
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var (
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CLOSED_ERR = fmt.Errorf("ResourcePool is closed")
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)
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// Factory is a function that can be used to create a resource.
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type Factory func() (Resource, error)
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// Every resource needs to suport the Resource interface.
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// Thread synchronization between Close() and IsClosed()
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// is the responsibility the caller.
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type Resource interface {
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Close()
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}
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// ResourcePool allows you to use a pool of resources.
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type ResourcePool struct {
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resources chan resourceWrapper
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factory Factory
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capacity sync2.AtomicInt64
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idleTimeout sync2.AtomicDuration
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// stats
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waitCount sync2.AtomicInt64
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waitTime sync2.AtomicDuration
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}
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type resourceWrapper struct {
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resource Resource
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timeUsed time.Time
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}
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// NewResourcePool creates a new ResourcePool pool.
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// capacity is the initial capacity of the pool.
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// maxCap is the maximum capacity.
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// If a resource is unused beyond idleTimeout, it's discarded.
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// An idleTimeout of 0 means that there is no timeout.
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func NewResourcePool(factory Factory, capacity, maxCap int, idleTimeout time.Duration) *ResourcePool {
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if capacity <= 0 || maxCap <= 0 || capacity > maxCap {
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panic(fmt.Errorf("Invalid/out of range capacity"))
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}
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rp := &ResourcePool{
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resources: make(chan resourceWrapper, maxCap),
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factory: factory,
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capacity: sync2.AtomicInt64(capacity),
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idleTimeout: sync2.AtomicDuration(idleTimeout),
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}
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for i := 0; i < capacity; i++ {
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rp.resources <- resourceWrapper{}
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}
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return rp
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}
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// Close empties the pool calling Close on all its resources.
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// You can call Close while there are outstanding resources.
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// It waits for all resources to be returned (Put).
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// After a Close, Get and TryGet are not allowed.
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func (rp *ResourcePool) Close() {
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rp.SetCapacity(0)
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}
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func (rp *ResourcePool) IsClosed() (closed bool) {
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return rp.capacity.Get() == 0
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}
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// Get will return the next available resource. If 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 (rp *ResourcePool) Get() (resource Resource, err error) {
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return rp.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 (rp *ResourcePool) TryGet() (resource Resource, err error) {
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return rp.get(false)
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}
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func (rp *ResourcePool) get(wait bool) (resource Resource, err error) {
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// Fetch
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var wrapper resourceWrapper
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var ok bool
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select {
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case wrapper, ok = <-rp.resources:
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default:
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if !wait {
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return nil, nil
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}
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startTime := time.Now()
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wrapper, ok = <-rp.resources
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rp.recordWait(startTime)
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}
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if !ok {
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return nil, CLOSED_ERR
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}
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// Unwrap
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timeout := rp.idleTimeout.Get()
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if wrapper.resource != nil && timeout > 0 && wrapper.timeUsed.Add(timeout).Sub(time.Now()) < 0 {
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wrapper.resource.Close()
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wrapper.resource = nil
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}
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if wrapper.resource == nil {
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wrapper.resource, err = rp.factory()
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if err != nil {
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rp.resources <- resourceWrapper{}
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}
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}
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return wrapper.resource, err
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}
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// Put will return a resource to the pool. For every successful Get,
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// a corresponding Put is required. If you no longer need a resource,
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// you will need to call Put(nil) instead of returning the closed resource.
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// The will eventually cause a new resource to be created in its place.
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func (rp *ResourcePool) Put(resource Resource) {
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var wrapper resourceWrapper
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if resource != nil {
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wrapper = resourceWrapper{resource, time.Now()}
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}
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select {
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case rp.resources <- wrapper:
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default:
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panic(fmt.Errorf("Attempt to Put into a full ResourcePool"))
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}
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}
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// SetCapacity changes the capacity of the pool.
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// You can use it to shrink or expand, but not beyond
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// the max capacity. If the change requires the pool
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// to be shrunk, SetCapacity waits till the necessary
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// number of resources are returned to the pool.
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// A SetCapacity of 0 is equivalent to closing the ResourcePool.
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func (rp *ResourcePool) SetCapacity(capacity int) error {
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if capacity < 0 || capacity > cap(rp.resources) {
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return fmt.Errorf("capacity %d is out of range", capacity)
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}
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// Atomically swap new capacity with old, but only
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// if old capacity is non-zero.
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var oldcap int
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for {
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oldcap = int(rp.capacity.Get())
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if oldcap == 0 {
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return CLOSED_ERR
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}
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if oldcap == capacity {
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return nil
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}
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if rp.capacity.CompareAndSwap(int64(oldcap), int64(capacity)) {
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break
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}
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}
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if capacity < oldcap {
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for i := 0; i < oldcap-capacity; i++ {
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wrapper := <-rp.resources
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if wrapper.resource != nil {
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wrapper.resource.Close()
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}
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}
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} else {
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for i := 0; i < capacity-oldcap; i++ {
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rp.resources <- resourceWrapper{}
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}
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}
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if capacity == 0 {
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close(rp.resources)
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}
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return nil
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}
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func (rp *ResourcePool) recordWait(start time.Time) {
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rp.waitCount.Add(1)
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rp.waitTime.Add(time.Now().Sub(start))
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}
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func (rp *ResourcePool) SetIdleTimeout(idleTimeout time.Duration) {
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rp.idleTimeout.Set(idleTimeout)
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}
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func (rp *ResourcePool) StatsJSON() string {
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c, a, mx, wc, wt, it := rp.Stats()
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return fmt.Sprintf(`{"Capacity": %v, "Available": %v, "MaxCapacity": %v, "WaitCount": %v, "WaitTime": %v, "IdleTimeout": %v}`, c, a, mx, wc, int64(wt), int64(it))
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}
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func (rp *ResourcePool) Stats() (capacity, available, maxCap, waitCount int64, waitTime, idleTimeout time.Duration) {
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return rp.Capacity(), rp.Available(), rp.MaxCap(), rp.WaitCount(), rp.WaitTime(), rp.IdleTimeout()
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}
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func (rp *ResourcePool) Capacity() int64 {
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return rp.capacity.Get()
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}
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func (rp *ResourcePool) Available() int64 {
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return int64(len(rp.resources))
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}
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func (rp *ResourcePool) MaxCap() int64 {
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return int64(cap(rp.resources))
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}
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func (rp *ResourcePool) WaitCount() int64 {
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return rp.waitCount.Get()
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}
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func (rp *ResourcePool) WaitTime() time.Duration {
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return rp.waitTime.Get()
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}
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func (rp *ResourcePool) IdleTimeout() time.Duration {
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return rp.idleTimeout.Get()
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}
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