cluster: don't silently drop messages when the write queue gets big

lib/child_process.js

@@ -329,11 +329,6 @@ function setupChannel(target, channel) {
       return;
     }
 
-    // For overflow protection don't write if channel queue is too deep.
-    if (channel.writeQueueSize > 1024 * 1024) {
-      return false;
-    }
-
     // package messages with a handle object
     if (handle) {
       // this message will be handled by an internalMessage event handler
@@ -379,7 +374,8 @@ function setupChannel(target, channel) {
 
     writeReq.oncomplete = nop;
 
-    return true;
+    /* If the master is > 2 read() calls behind, please stop sending. */
+    return channel.writeQueueSize < (65536 * 2);
   };
 
   target.connected = true;