Go 利用 buffer channel 做一个资源池

package pool

import (
  "errors"
  "io"
  "log"
  "sync"
)

type Pool struct {
  m         sync.Mutex
  closed    bool
  resources chan io.Closer
  fn        func() (io.Closer, error)
}

// 传入创建一个资源的函数，池大小
func New(fn func() (io.Closer, error), size uint) (*Pool, error) {
  if size <= 0 {
    return nil, errors.New("size not right")
  }

  return &Pool{
    resources: make(chan io.Closer, size),
    fn:        fn,
  }, nil
}

func (p *Pool) Acquire() (io.Closer, error) {
  select {
  case r, ok := <-p.resources:
    log.Println("Acquire one exist resource")
    if !ok {
      return nil, errors.New("closed")
    }
    return r, nil
  default:
    // 池内没有资源，需要创建一个
    log.Println("create one resource")
    return p.fn()
  }
}

func (p *Pool) Release(r io.Closer) {
  // 读取p.closed，Close()中有写p.close，避免多goroutine竞争，需要上锁
  p.m.Lock()
  defer p.m.Unlock()

  if p.closed {
    r.Close()
    return
  }

  select {
  case p.resources <- r: // 放回池里
    log.Println("put in ")
  default:
    // 池已经满了，需要关闭当前资源
    r.Close()
    log.Println("full close self ")
  }

  return
}

func (p *Pool) Close() {
  p.m.Lock()
  defer p.m.Unlock()

  if p.closed {
    return
  }

  p.closed = true

  // range channel时关闭channel
  close(p.resources)

  // 关闭池内所有资源
  for r := range p.resources {
    r.Close()
  }

  return

}