// Copyright 2015 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
// Transport code's client connection pooling.
package http2
import (
"crypto/tls"
"net/http"
"sync"
)
// ClientConnPool manages a pool of HTTP/2 client connections.
type ClientConnPool interface {
GetClientConn(req *http.Request, addr string) (*ClientConn, error)
MarkDead(*ClientConn)
}
// clientConnPoolIdleCloser is the interface implemented by ClientConnPool
// implementations which can close their idle connections.
type clientConnPoolIdleCloser interface {
ClientConnPool
closeIdleConnections()
}
var (
_ clientConnPoolIdleCloser = (*clientConnPool)(nil)
_ clientConnPoolIdleCloser = noDialClientConnPool{}
)
// TODO: use singleflight for dialing and addConnCalls?
type clientConnPool struct {
t *Transport
mu sync.Mutex // TODO: maybe switch to RWMutex
// TODO: add support for sharing conns based on cert names
// (e.g. share conn for googleapis.com and appspot.com)
conns map[string][]*ClientConn // key is host:port
dialing map[string]*dialCall // currently in-flight dials
keys map[*ClientConn][]string
addConnCalls map[string]*addConnCall // in-flight addConnIfNeede calls
}
func (p *clientConnPool) GetClientConn(req *http.Request, addr string) (*ClientConn, error) {
return p.getClientConn(req, addr, dialOnMiss)
}
const (
dialOnMiss = true
noDialOnMiss = false
)
func (p *clientConnPool) getClientConn(req *http.Request, addr string, dialOnMiss bool) (*ClientConn, error) {
if isConnectionCloseRequest(req) && dialOnMiss {
// It gets its own connection.
const singleUse = true
cc, err := p.t.dialClientConn(addr, singleUse)
if err != nil {
return nil, err
}
return cc, nil
}
p.mu.Lock()
for _, cc := range p.conns[addr] {
if cc.CanTakeNewRequest() {
p.mu.Unlock()
return cc, nil
}
}
if !dialOnMiss {
p.mu.Unlock()
return nil, ErrNoCachedConn
}
call := p.getStartDialLocked(addr)
p.mu.Unlock()
<-call.done
return call.res, call.err
}
// dialCall is an in-flight Transport dial call to a host.
type dialCall struct {
p *clientConnPool
done chan struct{} // closed when done
res *ClientConn // valid after done is closed
err error // valid after done is closed
}
// requires p.mu is held.
func (p *clientConnPool) getStartDialLocked(addr string) *dialCall {
if call, ok := p.dialing[addr]; ok {
// A dial is already in-flight. Don't start another.
return call
}
call := &dialCall{p: p, done: make(chan struct{})}
if p.dialing == nil {
p.dialing = make(map[string]*dialCall)
}
p.dialing[addr] = call
go call.dial(addr)
return call
}
// run in its own goroutine.
func (c *dialCall) dial(addr string) {
const singleUse = false // shared conn
c.res, c.err = c.p.t.dialClientConn(addr, singleUse)
close(c.done)
c.p.mu.Lock()
delete(c.p.dialing, addr)
if c.err == nil {
c.p.addConnLocked(addr, c.res)
}
c.p.mu.Unlock()
}
// addConnIfNeeded makes a NewClientConn out of c if a connection for key doesn't
// already exist. It coalesces concurrent calls with the same key.
// This is used by the http1 Transport code when it creates a new connection. Because
// the http1 Transport doesn't de-dup TCP dials to outbound hosts (because it doesn't know
// the protocol), it can get into a situation where it has multiple TLS connections.
// This code decides which ones live or die.
// The return value used is whether c was used.
// c is never closed.
func (p *clientConnPool) addConnIfNeeded(key string, t *Transport, c *tls.Conn) (used bool, err error) {
p.mu.Lock()
for _, cc := range p.conns[key] {
if cc.CanTakeNewRequest() {
p.mu.Unlock()
return false, nil
}
}
call, dup := p.addConnCalls[key]
if !dup {
if p.addConnCalls == nil {
p.addConnCalls = make(map[string]*addConnCall)
}
call = &addConnCall{
p: p,
done: make(chan struct{}),
}
p.addConnCalls[key] = call
go call.run(t, key, c)
}
p.mu.Unlock()
<-call.done
if call.err != nil {
return false, call.err
}
return !dup, nil
}
type addConnCall struct {
p *clientConnPool
done chan struct{} // closed when done
err error
}
func (c *addConnCall) run(t *Transport, key string, tc *tls.Conn) {
cc, err := t.NewClientConn(tc)
p := c.p
p.mu.Lock()
if err != nil {
c.err = err
} else {
p.addConnLocked(key, cc)
}
delete(p.addConnCalls, key)
p.mu.Unlock()
close(c.done)
}
func (p *clientConnPool) addConn(key string, cc *ClientConn) {
p.mu.Lock()
p.addConnLocked(key, cc)
p.mu.Unlock()
}
// p.mu must be held
func (p *clientConnPool) addConnLocked(key string, cc *ClientConn) {
for _, v := range p.conns[key] {
if v == cc {
return
}
}
if p.conns == nil {
p.conns = make(map[string][]*ClientConn)
}
if p.keys == nil {
p.keys = make(map[*ClientConn][]string)
}
p.conns[key] = append(p.conns[key], cc)
p.keys[cc] = append(p.keys[cc], key)
}
func (p *clientConnPool) MarkDead(cc *ClientConn) {
p.mu.Lock()
defer p.mu.Unlock()
for _, key := range p.keys[cc] {
vv, ok := p.conns[key]
if !ok {
continue
}
newList := filterOutClientConn(vv, cc)
if len(newList) > 0 {
p.conns[key] = newList
} else {
delete(p.conns, key)
}
}
delete(p.keys, cc)
}
func (p *clientConnPool) closeIdleConnections() {
p.mu.Lock()
defer p.mu.Unlock()
// TODO: don't close a cc if it was just added to the pool
// milliseconds ago and has never been used. There's currently
// a small race window with the HTTP/1 Transport's integration
// where it can add an idle conn just before using it, and
// somebody else can concurrently call CloseIdleConns and
// break some caller's RoundTrip.
for _, vv := range p.conns {
for _, cc := range vv {
cc.closeIfIdle()
}
}
}
func filterOutClientConn(in []*ClientConn, exclude *ClientConn) []*ClientConn {
out := in[:0]
for _, v := range in {
if v != exclude {
out = append(out, v)
}
}
// If we filtered it out, zero out the last item to prevent
// the GC from seeing it.
if len(in) != len(out) {
in[len(in)-1] = nil
}
return out
}
// noDialClientConnPool is an implementation of http2.ClientConnPool
// which never dials. We let the HTTP/1.1 client dial and use its TLS
// connection instead.
type noDialClientConnPool struct{ *clientConnPool }
func (p noDialClientConnPool) GetClientConn(req *http.Request, addr string) (*ClientConn, error) {
return p.getClientConn(req, addr, noDialOnMiss)
}