child_process: reduce nextTick() usage

PR-URL: https://github.com/nodejs/node/pull/13459
Reviewed-By: Refael Ackermann <refack@gmail.com>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>

benchmark/cluster/echo.js

@@ -0,0 +1,70 @@
+'use strict';
+
+const cluster = require('cluster');
+if (cluster.isMaster) {
+  const common = require('../common.js');
+  const bench = common.createBenchmark(main, {
+    workers: [1],
+    payload: ['string', 'object'],
+    sendsPerBroadcast: [1, 10],
+    n: [1e5]
+  });
+
+  function main(conf) {
+    var n = +conf.n;
+    var workers = +conf.workers;
+    var sends = +conf.sendsPerBroadcast;
+    var expectedPerBroadcast = sends * workers;
+    var payload;
+    var readies = 0;
+    var broadcasts = 0;
+    var msgCount = 0;
+
+    switch (conf.payload) {
+      case 'string':
+        payload = 'hello world!';
+        break;
+      case 'object':
+        payload = { action: 'pewpewpew', powerLevel: 9001 };
+        break;
+      default:
+        throw new Error('Unsupported payload type');
+    }
+
+    for (var i = 0; i < workers; ++i)
+      cluster.fork().on('online', onOnline).on('message', onMessage);
+
+    function onOnline(msg) {
+      if (++readies === workers) {
+        bench.start();
+        broadcast();
+      }
+    }
+
+    function broadcast() {
+      var id;
+      if (broadcasts++ === n) {
+        bench.end(n);
+        for (id in cluster.workers)
+          cluster.workers[id].disconnect();
+        return;
+      }
+      for (id in cluster.workers) {
+        const worker = cluster.workers[id];
+        for (var i = 0; i < sends; ++i)
+          worker.send(payload);
+      }
+    }
+
+    function onMessage(msg) {
+      if (++msgCount === expectedPerBroadcast) {
+        msgCount = 0;
+        broadcast();
+      }
+    }
+  }
+} else {
+  process.on('message', function(msg) {
+    process.send(msg);
+  });
+}

lib/internal/child_process.js

@@ -456,16 +456,22 @@ function setupChannel(target, channel) {
       }
       chunks[0] = jsonBuffer + chunks[0];
 
+      var nextTick = false;
       for (var i = 0; i < numCompleteChunks; i++) {
         var message = JSON.parse(chunks[i]);
 
         // There will be at most one NODE_HANDLE message in every chunk we
         // read because SCM_RIGHTS messages don't get coalesced. Make sure
         // that we deliver the handle with the right message however.
-        if (message && message.cmd === 'NODE_HANDLE')
-          handleMessage(target, message, recvHandle);
-        else
-          handleMessage(target, message, undefined);
+        if (isInternal(message)) {
+          if (message.cmd === 'NODE_HANDLE')
+            handleMessage(message, recvHandle, true, false);
+          else
+            handleMessage(message, undefined, true, false);
+        } else {
+          handleMessage(message, undefined, false, nextTick);
+          nextTick = true;
+        }
       }
       jsonBuffer = incompleteChunk;
       this.buffering = jsonBuffer.length !== 0;
@@ -526,7 +532,7 @@ function setupChannel(target, channel) {
 
     // Convert handle object
     obj.got.call(this, message, handle, function(handle) {
-      handleMessage(target, message.msg, handle);
+      handleMessage(message.msg, handle, isInternal(message.msg), false);
     });
   });
 
@@ -732,27 +738,32 @@ function setupChannel(target, channel) {
     process.nextTick(finish);
   };
 
+  function emit(event, message, handle) {
+    target.emit(event, message, handle);
+  }
+
+  function handleMessage(message, handle, internal, nextTick) {
+    if (!target.channel)
+      return;
+
+    var eventName = (internal ? 'internalMessage' : 'message');
+    if (nextTick)
+      process.nextTick(emit, eventName, message, handle);
+    else
+      target.emit(eventName, message, handle);
+  }
+
   channel.readStart();
   return control;
 }
 
-
 const INTERNAL_PREFIX = 'NODE_';
-function handleMessage(target, message, handle) {
-  if (!target.channel)
-    return;
-
-  var eventName = 'message';
-  if (message !== null &&
-      typeof message === 'object' &&
-      typeof message.cmd === 'string' &&
-      message.cmd.length > INTERNAL_PREFIX.length &&
-      message.cmd.slice(0, INTERNAL_PREFIX.length) === INTERNAL_PREFIX) {
-    eventName = 'internalMessage';
-  }
-  process.nextTick(() => {
-    target.emit(eventName, message, handle);
-  });
+function isInternal(message) {
+  return (message !== null &&
+          typeof message === 'object' &&
+          typeof message.cmd === 'string' &&
+          message.cmd.length > INTERNAL_PREFIX.length &&
+          message.cmd.slice(0, INTERNAL_PREFIX.length) === INTERNAL_PREFIX);
 }
 
 function nop() { }