Increase writeRequestsCh channel buffer size (apache#277)

* Increase writeRequestsCh channel buffer size

* Fixed indentation

pulsar/internal/connection.go

@@ -181,9 +181,15 @@ func newConnection(logicalAddr *url.URL, physicalAddr *url.URL, tlsOptions *TLSO
 		closeCh:            make(chan interface{}),
 		incomingRequestsCh: make(chan *request, 10),
 		incomingCmdCh:      make(chan *incomingCmd, 10),
-		writeRequestsCh:    make(chan []byte, 10),
-		listeners:          make(map[uint64]ConnectionListener),
-		consumerHandlers:   make(map[uint64]ConsumerHandler),
+
+		// This channel is used to pass data from producers to the connection
+		// go routine. It can become contended or blocking if we have multiple
+		// partition produces writing on a single connection. In general it's
+		// good to keep this above the number of partition producers assigned
+		// to a single connection.
+		writeRequestsCh:  make(chan []byte, 256),
+		listeners:        make(map[uint64]ConnectionListener),
+		consumerHandlers: make(map[uint64]ConsumerHandler),
 	}
 	cnx.reader = newConnectionReader(cnx)
 	cnx.cond = sync.NewCond(cnx)