Scott Baker | 2d89798 | 2019-09-24 11:50:08 -0700 | [diff] [blame^] | 1 | // Copyright 2015 The Go Authors. All rights reserved. |
| 2 | // Use of this source code is governed by a BSD-style |
| 3 | // license that can be found in the LICENSE file. |
| 4 | |
| 5 | // Transport code's client connection pooling. |
| 6 | |
| 7 | package http2 |
| 8 | |
| 9 | import ( |
| 10 | "crypto/tls" |
| 11 | "net/http" |
| 12 | "sync" |
| 13 | ) |
| 14 | |
| 15 | // ClientConnPool manages a pool of HTTP/2 client connections. |
| 16 | type ClientConnPool interface { |
| 17 | GetClientConn(req *http.Request, addr string) (*ClientConn, error) |
| 18 | MarkDead(*ClientConn) |
| 19 | } |
| 20 | |
| 21 | // clientConnPoolIdleCloser is the interface implemented by ClientConnPool |
| 22 | // implementations which can close their idle connections. |
| 23 | type clientConnPoolIdleCloser interface { |
| 24 | ClientConnPool |
| 25 | closeIdleConnections() |
| 26 | } |
| 27 | |
| 28 | var ( |
| 29 | _ clientConnPoolIdleCloser = (*clientConnPool)(nil) |
| 30 | _ clientConnPoolIdleCloser = noDialClientConnPool{} |
| 31 | ) |
| 32 | |
| 33 | // TODO: use singleflight for dialing and addConnCalls? |
| 34 | type clientConnPool struct { |
| 35 | t *Transport |
| 36 | |
| 37 | mu sync.Mutex // TODO: maybe switch to RWMutex |
| 38 | // TODO: add support for sharing conns based on cert names |
| 39 | // (e.g. share conn for googleapis.com and appspot.com) |
| 40 | conns map[string][]*ClientConn // key is host:port |
| 41 | dialing map[string]*dialCall // currently in-flight dials |
| 42 | keys map[*ClientConn][]string |
| 43 | addConnCalls map[string]*addConnCall // in-flight addConnIfNeede calls |
| 44 | } |
| 45 | |
| 46 | func (p *clientConnPool) GetClientConn(req *http.Request, addr string) (*ClientConn, error) { |
| 47 | return p.getClientConn(req, addr, dialOnMiss) |
| 48 | } |
| 49 | |
| 50 | const ( |
| 51 | dialOnMiss = true |
| 52 | noDialOnMiss = false |
| 53 | ) |
| 54 | |
| 55 | // shouldTraceGetConn reports whether getClientConn should call any |
| 56 | // ClientTrace.GetConn hook associated with the http.Request. |
| 57 | // |
| 58 | // This complexity is needed to avoid double calls of the GetConn hook |
| 59 | // during the back-and-forth between net/http and x/net/http2 (when the |
| 60 | // net/http.Transport is upgraded to also speak http2), as well as support |
| 61 | // the case where x/net/http2 is being used directly. |
| 62 | func (p *clientConnPool) shouldTraceGetConn(st clientConnIdleState) bool { |
| 63 | // If our Transport wasn't made via ConfigureTransport, always |
| 64 | // trace the GetConn hook if provided, because that means the |
| 65 | // http2 package is being used directly and it's the one |
| 66 | // dialing, as opposed to net/http. |
| 67 | if _, ok := p.t.ConnPool.(noDialClientConnPool); !ok { |
| 68 | return true |
| 69 | } |
| 70 | // Otherwise, only use the GetConn hook if this connection has |
| 71 | // been used previously for other requests. For fresh |
| 72 | // connections, the net/http package does the dialing. |
| 73 | return !st.freshConn |
| 74 | } |
| 75 | |
| 76 | func (p *clientConnPool) getClientConn(req *http.Request, addr string, dialOnMiss bool) (*ClientConn, error) { |
| 77 | if isConnectionCloseRequest(req) && dialOnMiss { |
| 78 | // It gets its own connection. |
| 79 | traceGetConn(req, addr) |
| 80 | const singleUse = true |
| 81 | cc, err := p.t.dialClientConn(addr, singleUse) |
| 82 | if err != nil { |
| 83 | return nil, err |
| 84 | } |
| 85 | return cc, nil |
| 86 | } |
| 87 | p.mu.Lock() |
| 88 | for _, cc := range p.conns[addr] { |
| 89 | if st := cc.idleState(); st.canTakeNewRequest { |
| 90 | if p.shouldTraceGetConn(st) { |
| 91 | traceGetConn(req, addr) |
| 92 | } |
| 93 | p.mu.Unlock() |
| 94 | return cc, nil |
| 95 | } |
| 96 | } |
| 97 | if !dialOnMiss { |
| 98 | p.mu.Unlock() |
| 99 | return nil, ErrNoCachedConn |
| 100 | } |
| 101 | traceGetConn(req, addr) |
| 102 | call := p.getStartDialLocked(addr) |
| 103 | p.mu.Unlock() |
| 104 | <-call.done |
| 105 | return call.res, call.err |
| 106 | } |
| 107 | |
| 108 | // dialCall is an in-flight Transport dial call to a host. |
| 109 | type dialCall struct { |
| 110 | p *clientConnPool |
| 111 | done chan struct{} // closed when done |
| 112 | res *ClientConn // valid after done is closed |
| 113 | err error // valid after done is closed |
| 114 | } |
| 115 | |
| 116 | // requires p.mu is held. |
| 117 | func (p *clientConnPool) getStartDialLocked(addr string) *dialCall { |
| 118 | if call, ok := p.dialing[addr]; ok { |
| 119 | // A dial is already in-flight. Don't start another. |
| 120 | return call |
| 121 | } |
| 122 | call := &dialCall{p: p, done: make(chan struct{})} |
| 123 | if p.dialing == nil { |
| 124 | p.dialing = make(map[string]*dialCall) |
| 125 | } |
| 126 | p.dialing[addr] = call |
| 127 | go call.dial(addr) |
| 128 | return call |
| 129 | } |
| 130 | |
| 131 | // run in its own goroutine. |
| 132 | func (c *dialCall) dial(addr string) { |
| 133 | const singleUse = false // shared conn |
| 134 | c.res, c.err = c.p.t.dialClientConn(addr, singleUse) |
| 135 | close(c.done) |
| 136 | |
| 137 | c.p.mu.Lock() |
| 138 | delete(c.p.dialing, addr) |
| 139 | if c.err == nil { |
| 140 | c.p.addConnLocked(addr, c.res) |
| 141 | } |
| 142 | c.p.mu.Unlock() |
| 143 | } |
| 144 | |
| 145 | // addConnIfNeeded makes a NewClientConn out of c if a connection for key doesn't |
| 146 | // already exist. It coalesces concurrent calls with the same key. |
| 147 | // This is used by the http1 Transport code when it creates a new connection. Because |
| 148 | // the http1 Transport doesn't de-dup TCP dials to outbound hosts (because it doesn't know |
| 149 | // the protocol), it can get into a situation where it has multiple TLS connections. |
| 150 | // This code decides which ones live or die. |
| 151 | // The return value used is whether c was used. |
| 152 | // c is never closed. |
| 153 | func (p *clientConnPool) addConnIfNeeded(key string, t *Transport, c *tls.Conn) (used bool, err error) { |
| 154 | p.mu.Lock() |
| 155 | for _, cc := range p.conns[key] { |
| 156 | if cc.CanTakeNewRequest() { |
| 157 | p.mu.Unlock() |
| 158 | return false, nil |
| 159 | } |
| 160 | } |
| 161 | call, dup := p.addConnCalls[key] |
| 162 | if !dup { |
| 163 | if p.addConnCalls == nil { |
| 164 | p.addConnCalls = make(map[string]*addConnCall) |
| 165 | } |
| 166 | call = &addConnCall{ |
| 167 | p: p, |
| 168 | done: make(chan struct{}), |
| 169 | } |
| 170 | p.addConnCalls[key] = call |
| 171 | go call.run(t, key, c) |
| 172 | } |
| 173 | p.mu.Unlock() |
| 174 | |
| 175 | <-call.done |
| 176 | if call.err != nil { |
| 177 | return false, call.err |
| 178 | } |
| 179 | return !dup, nil |
| 180 | } |
| 181 | |
| 182 | type addConnCall struct { |
| 183 | p *clientConnPool |
| 184 | done chan struct{} // closed when done |
| 185 | err error |
| 186 | } |
| 187 | |
| 188 | func (c *addConnCall) run(t *Transport, key string, tc *tls.Conn) { |
| 189 | cc, err := t.NewClientConn(tc) |
| 190 | |
| 191 | p := c.p |
| 192 | p.mu.Lock() |
| 193 | if err != nil { |
| 194 | c.err = err |
| 195 | } else { |
| 196 | p.addConnLocked(key, cc) |
| 197 | } |
| 198 | delete(p.addConnCalls, key) |
| 199 | p.mu.Unlock() |
| 200 | close(c.done) |
| 201 | } |
| 202 | |
| 203 | func (p *clientConnPool) addConn(key string, cc *ClientConn) { |
| 204 | p.mu.Lock() |
| 205 | p.addConnLocked(key, cc) |
| 206 | p.mu.Unlock() |
| 207 | } |
| 208 | |
| 209 | // p.mu must be held |
| 210 | func (p *clientConnPool) addConnLocked(key string, cc *ClientConn) { |
| 211 | for _, v := range p.conns[key] { |
| 212 | if v == cc { |
| 213 | return |
| 214 | } |
| 215 | } |
| 216 | if p.conns == nil { |
| 217 | p.conns = make(map[string][]*ClientConn) |
| 218 | } |
| 219 | if p.keys == nil { |
| 220 | p.keys = make(map[*ClientConn][]string) |
| 221 | } |
| 222 | p.conns[key] = append(p.conns[key], cc) |
| 223 | p.keys[cc] = append(p.keys[cc], key) |
| 224 | } |
| 225 | |
| 226 | func (p *clientConnPool) MarkDead(cc *ClientConn) { |
| 227 | p.mu.Lock() |
| 228 | defer p.mu.Unlock() |
| 229 | for _, key := range p.keys[cc] { |
| 230 | vv, ok := p.conns[key] |
| 231 | if !ok { |
| 232 | continue |
| 233 | } |
| 234 | newList := filterOutClientConn(vv, cc) |
| 235 | if len(newList) > 0 { |
| 236 | p.conns[key] = newList |
| 237 | } else { |
| 238 | delete(p.conns, key) |
| 239 | } |
| 240 | } |
| 241 | delete(p.keys, cc) |
| 242 | } |
| 243 | |
| 244 | func (p *clientConnPool) closeIdleConnections() { |
| 245 | p.mu.Lock() |
| 246 | defer p.mu.Unlock() |
| 247 | // TODO: don't close a cc if it was just added to the pool |
| 248 | // milliseconds ago and has never been used. There's currently |
| 249 | // a small race window with the HTTP/1 Transport's integration |
| 250 | // where it can add an idle conn just before using it, and |
| 251 | // somebody else can concurrently call CloseIdleConns and |
| 252 | // break some caller's RoundTrip. |
| 253 | for _, vv := range p.conns { |
| 254 | for _, cc := range vv { |
| 255 | cc.closeIfIdle() |
| 256 | } |
| 257 | } |
| 258 | } |
| 259 | |
| 260 | func filterOutClientConn(in []*ClientConn, exclude *ClientConn) []*ClientConn { |
| 261 | out := in[:0] |
| 262 | for _, v := range in { |
| 263 | if v != exclude { |
| 264 | out = append(out, v) |
| 265 | } |
| 266 | } |
| 267 | // If we filtered it out, zero out the last item to prevent |
| 268 | // the GC from seeing it. |
| 269 | if len(in) != len(out) { |
| 270 | in[len(in)-1] = nil |
| 271 | } |
| 272 | return out |
| 273 | } |
| 274 | |
| 275 | // noDialClientConnPool is an implementation of http2.ClientConnPool |
| 276 | // which never dials. We let the HTTP/1.1 client dial and use its TLS |
| 277 | // connection instead. |
| 278 | type noDialClientConnPool struct{ *clientConnPool } |
| 279 | |
| 280 | func (p noDialClientConnPool) GetClientConn(req *http.Request, addr string) (*ClientConn, error) { |
| 281 | return p.getClientConn(req, addr, noDialOnMiss) |
| 282 | } |