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authorFelix Lange <fjl@twurst.com>2015-04-10 23:24:41 +0800
committerFelix Lange <fjl@twurst.com>2015-04-10 23:24:41 +0800
commitc5332537f5726610c3c1606ead8cbaa83144b537 (patch)
tree7cdf4fce82ff599fcd86aa01bd952ddf310fb2f1
parent56977c225ecbf7834e380c03714c3e8d70e0b184 (diff)
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p2p: limit number of lingering inbound pre-handshake connections
This is supposed to apply some back pressure so Server is not accepting more connections than it can actually handle. The current limit is 50. This doesn't really need to be configurable, but we'll see how it behaves in our test nodes and adjust accordingly.
-rw-r--r--p2p/server.go20
1 files changed, 19 insertions, 1 deletions
diff --git a/p2p/server.go b/p2p/server.go
index 7b880f77b..5cd3dc2ad 100644
--- a/p2p/server.go
+++ b/p2p/server.go
@@ -21,6 +21,11 @@ const (
defaultDialTimeout = 10 * time.Second
refreshPeersInterval = 30 * time.Second
+ // This is the maximum number of inbound connection
+ // that are allowed to linger between 'accepted' and
+ // 'added as peer'.
+ maxAcceptConns = 50
+
// total timeout for encryption handshake and protocol
// handshake in both directions.
handshakeTimeout = 5 * time.Second
@@ -269,15 +274,28 @@ func (srv *Server) Self() *discover.Node {
// main loop for adding connections via listening
func (srv *Server) listenLoop() {
defer srv.loopWG.Done()
+
+ // This channel acts as a semaphore limiting
+ // active inbound connections that are lingering pre-handshake.
+ // If all slots are taken, no further connections are accepted.
+ slots := make(chan struct{}, maxAcceptConns)
+ for i := 0; i < maxAcceptConns; i++ {
+ slots <- struct{}{}
+ }
+
glog.V(logger.Info).Infoln("Listening on", srv.listener.Addr())
for {
+ <-slots
conn, err := srv.listener.Accept()
if err != nil {
return
}
glog.V(logger.Debug).Infof("Accepted conn %v\n", conn.RemoteAddr())
srv.peerWG.Add(1)
- go srv.startPeer(conn, nil)
+ go func() {
+ srv.startPeer(conn, nil)
+ slots <- struct{}{}
+ }()
}
}