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|
// Tideland Go Library - Redis Client - resp Pool
//
// Copyright (C) 2009-2017 Frank Mueller / Oldenburg / Germany
//
// All rights reserved. Use of this source code is governed
// by the new BSD license.
package redis
//--------------------
// IMPORTS
//--------------------
import (
"time"
"github.com/tideland/golib/errors"
"github.com/tideland/golib/loop"
)
//--------------------
// CONNECTION POOL
//--------------------
const (
forcedPull = true
unforcedPull = false
forcedPullRequest = iota
unforcedPullRequest
pushRequest
killRequest
closeRequest
)
// poolResponse is returned as result of a pool request.
type poolResponse struct {
resp *resp
err error
}
type poolRequest struct {
kind int
resp *resp
responseChan chan *poolResponse
}
// pool manages a number of Redis resp instances.
type pool struct {
database *Database
available map[*resp]*resp
inUse map[*resp]*resp
backend loop.Loop
requestChan chan *poolRequest
}
// newPool creates a connection pool with uninitialized
// protocol instances.
func newPool(db *Database) *pool {
p := &pool{
database: db,
available: make(map[*resp]*resp),
inUse: make(map[*resp]*resp),
requestChan: make(chan *poolRequest),
}
p.backend = loop.Go(p.backendLoop, "redis", db.address, db.index)
return p
}
// pull returns a protocol out of the pool. If none is available
// but the configured pool sized isn't reached a new one will be
// established.
func (p *pool) pull(forced bool) (*resp, error) {
if forced {
return p.do(forcedPullRequest, nil)
}
wait := 5 * time.Millisecond
for i := 0; i < 5; i++ {
resp, err := p.do(unforcedPullRequest, nil)
if err != nil {
return nil, err
}
if resp != nil {
return resp, nil
}
time.Sleep(wait)
wait = wait * 2
}
return nil, errors.New(ErrPoolLimitReached, errorMessages, p.database.poolsize)
}
// push returns a protocol back into the pool.
func (p *pool) push(resp *resp) error {
_, err := p.do(pushRequest, resp)
return err
}
// kill closes the connection and removes it from the pool.
func (p *pool) kill(resp *resp) error {
_, err := p.do(killRequest, resp)
return err
}
// close closes all pooled protocol instances, first the available ones,
// then the ones in use.
func (p *pool) close() error {
_, err := p.do(closeRequest, nil)
return err
}
// do executes one request.
func (p *pool) do(kind int, resp *resp) (*resp, error) {
request := &poolRequest{
kind: kind,
resp: resp,
responseChan: make(chan *poolResponse, 1),
}
p.requestChan <- request
response := <-request.responseChan
return response.resp, response.err
}
// respond answers to a request.
func (p *pool) respond(request *poolRequest, resp *resp, err error) {
response := &poolResponse{
resp: resp,
err: err,
}
request.responseChan <- response
}
// backendLoop manages the pool in a serialized way.
func (p *pool) backendLoop(l loop.Loop) error {
for {
select {
case <-l.ShallStop():
return nil
case request := <-p.requestChan:
// Handle the request.
switch request.kind {
case forcedPullRequest:
// Always return a new protocol.
resp, err := newResp(p.database)
if err != nil {
p.respond(request, nil, err)
} else {
p.respond(request, resp, nil)
}
case unforcedPullRequest:
// Fetch a protocol out of the pool.
switch {
case len(p.available) > 0:
fetch:
for resp := range p.available {
delete(p.available, resp)
p.inUse[resp] = resp
p.respond(request, resp, nil)
break fetch
}
case len(p.inUse) < p.database.poolsize:
resp, err := newResp(p.database)
if err != nil {
p.respond(request, nil, err)
} else {
p.respond(request, resp, nil)
}
default:
p.respond(request, nil, nil)
}
case pushRequest:
// Return a protocol.
delete(p.inUse, request.resp)
if len(p.available) < p.database.poolsize {
p.available[request.resp] = request.resp
p.respond(request, nil, nil)
} else {
p.respond(request, nil, request.resp.close())
}
case killRequest:
// Close w/o reusing.
delete(p.inUse, request.resp)
p.respond(request, nil, request.resp.close())
case closeRequest:
// Close all protocols.
for resp := range p.available {
resp.close()
}
for resp := range p.inUse {
resp.close()
}
p.respond(request, nil, nil)
}
}
}
}
// EOF
|
