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pool.go
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pool.go
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// Modified from https://github.com/garyburd/redigo/blob/master/redis/pool.go
// Copyright 2012 Gary Burd
//
// Licensed under the Apache License, Version 2.0 (the "License"): you may
// not use this file except in compliance with the License. You may obtain
// a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
// WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
// License for the specific language governing permissions and limitations
// under the License.
package dilithium
import (
"container/list"
"errors"
"sync"
"time"
)
var nowFunc = time.Now // for testing
var errPoolClosed = errors.New("dilithium: connection pool closed")
// Pool maintains a pool of connections. The application calls the Get method
// to get a connection from the pool and the connection's Close method to
// return the connection's resources to the pool.
type Pool struct {
// Dial is an application supplied function for creating new connections.
Dial func(url string) (Closer, error)
// TestOnBorrow is an optional application supplied function for checking
// the health of an idle connection before the connection is used again by
// the application. Argument t is the time that the connection was returned
// to the pool. If the function returns an error, then the connection is
// closed.
TestOnBorrow func(c Closer, t time.Time) error
// Maximum number of idle connections in the pool.
MaxIdle int
// Close connections after remaining idle for this duration. If the value
// is zero, then idle connections are not closed. Applications should set
// the timeout to a value less than the server's timeout.
IdleTimeout time.Duration
// url is the connection string used by Dial, typically a URL
url string
// mu protects fields defined below.
mu sync.Mutex
closed bool
// Stack of idleConn with most recently used at the front.
idle list.List
}
type Closer interface {
Close()
}
type idleConn struct {
c Closer
t time.Time
}
// NewPool returns a pool that uses newPool to create connections as needed.
// The pool keeps a maximum of maxIdle idle connections.
func NewPool(newFn func(string) (Closer, error), maxIdle int) *Pool {
return &Pool{Dial: newFn, MaxIdle: maxIdle}
}
// Get gets a connection from the pool.
func (p *Pool) Get() (*pooledConnection, error) {
c := &pooledConnection{p: p}
err := c.get()
return c, err
}
// Close releases the resources used by the pool.
func (p *Pool) Close() {
p.mu.Lock()
idle := p.idle
p.idle.Init()
p.closed = true
p.mu.Unlock()
for e := idle.Front(); e != nil; e = e.Next() {
e.Value.(idleConn).c.Close()
}
}
// get prunes stale connections and returns a connection from the idle list or
// creates a new connection.
func (p *Pool) get() (Closer, error) {
p.mu.Lock()
if p.closed {
p.mu.Unlock()
return nil, errors.New("dilithium: get on closed pool")
}
// Prune stale connections.
if timeout := p.IdleTimeout; timeout > 0 {
for i, n := 0, p.idle.Len(); i < n; i++ {
e := p.idle.Back()
if e == nil {
break
}
ic := e.Value.(idleConn)
if ic.t.Add(timeout).After(nowFunc()) {
break
}
p.idle.Remove(e)
p.mu.Unlock()
ic.c.Close()
p.mu.Lock()
}
}
// Get idle connection.
for i, n := 0, p.idle.Len(); i < n; i++ {
e := p.idle.Front()
if e == nil {
break
}
ic := e.Value.(idleConn)
p.idle.Remove(e)
test := p.TestOnBorrow
p.mu.Unlock()
if test != nil && test(ic.c, ic.t) != nil {
ic.c.Close()
} else {
return ic.c, nil
}
p.mu.Lock()
}
// No idle connection, create new.
dial := p.Dial
p.mu.Unlock()
return dial(p.url)
}
func (p *Pool) put(c Closer) {
p.mu.Lock()
if !p.closed {
p.idle.PushFront(idleConn{t: nowFunc(), c: c})
if p.idle.Len() > p.MaxIdle {
c = p.idle.Remove(p.idle.Back()).(idleConn).c
} else {
c = nil
}
}
p.mu.Unlock()
if c != nil {
c.Close()
}
}
type pooledConnection struct {
c Closer
err error
p *Pool
}
func (c *pooledConnection) get() error {
if c.err == nil && c.c == nil {
c.c, c.err = c.p.get()
}
return c.err
}
func (c *pooledConnection) Close() {
if c.c != nil {
c.p.put(c.c)
c.c = nil
c.err = errPoolClosed
}
}
func (c *pooledConnection) Err() error {
if err := c.get(); err != nil {
return err
}
return nil
}
var (
poolTypes = make(map[string]*Pool)
poolTypesMtx sync.RWMutex
)
func RegisterPoolType(name string, pool *Pool) {
poolTypesMtx.Lock()
defer poolTypesMtx.Unlock()
poolTypes[name] = pool
}