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-rw-r--r--vendor/google.golang.org/appengine/internal/net.go56
1 files changed, 56 insertions, 0 deletions
diff --git a/vendor/google.golang.org/appengine/internal/net.go b/vendor/google.golang.org/appengine/internal/net.go
new file mode 100644
index 000000000..3b94cf0c6
--- /dev/null
+++ b/vendor/google.golang.org/appengine/internal/net.go
@@ -0,0 +1,56 @@
+// Copyright 2014 Google Inc. All rights reserved.
+// Use of this source code is governed by the Apache 2.0
+// license that can be found in the LICENSE file.
+
+package internal
+
+// This file implements a network dialer that limits the number of concurrent connections.
+// It is only used for API calls.
+
+import (
+ "log"
+ "net"
+ "runtime"
+ "sync"
+ "time"
+)
+
+var limitSem = make(chan int, 100) // TODO(dsymonds): Use environment variable.
+
+func limitRelease() {
+ // non-blocking
+ select {
+ case <-limitSem:
+ default:
+ // This should not normally happen.
+ log.Print("appengine: unbalanced limitSem release!")
+ }
+}
+
+func limitDial(network, addr string) (net.Conn, error) {
+ limitSem <- 1
+
+ // Dial with a timeout in case the API host is MIA.
+ // The connection should normally be very fast.
+ conn, err := net.DialTimeout(network, addr, 500*time.Millisecond)
+ if err != nil {
+ limitRelease()
+ return nil, err
+ }
+ lc := &limitConn{Conn: conn}
+ runtime.SetFinalizer(lc, (*limitConn).Close) // shouldn't usually be required
+ return lc, nil
+}
+
+type limitConn struct {
+ close sync.Once
+ net.Conn
+}
+
+func (lc *limitConn) Close() error {
+ defer lc.close.Do(func() {
+ limitRelease()
+ runtime.SetFinalizer(lc, nil)
+ })
+ return lc.Conn.Close()
+}