src: setup cluster workers before preloading

We need to process cluster workers before any preload modules is
executed. Otherwise, the child processes are not correctly disovered
as clustered workers inside the preloaded modules.

Fixes: nodejs#1269

src/node.js

@@ -71,6 +71,17 @@
     } else {
       // There is user code to be run
 
+      // If this is a worker in cluster mode, start up the communication
+      // channel. This needs to be done before any user code gets executed
+      // (including preload modules).
+      if (process.argv[1] && process.env.NODE_UNIQUE_ID) {
+        var cluster = NativeModule.require('cluster');
+        cluster._setupWorker();
+
+        // Make sure it's not accidentally inherited by child processes.
+        delete process.env.NODE_UNIQUE_ID;
+      }
+
       // Load any preload modules
       if (process._preload_modules) {
         var Module = NativeModule.require('module');
@@ -87,16 +98,6 @@
         var path = NativeModule.require('path');
         process.argv[1] = path.resolve(process.argv[1]);
 
-        // If this is a worker in cluster mode, start up the communication
-        // channel.
-        if (process.env.NODE_UNIQUE_ID) {
-          var cluster = NativeModule.require('cluster');
-          cluster._setupWorker();
-
-          // Make sure it's not accidentally inherited by child processes.
-          delete process.env.NODE_UNIQUE_ID;
-        }
-
         var Module = NativeModule.require('module');
 
         if (global.v8debug &&

test/fixtures/cluster-preload-test.js

@@ -0,0 +1,7 @@
+var cluster = require('cluster');
+if (cluster.isMaster) {
+  cluster.fork(); // one child
+  cluster.on('exit', function(worker, code, signal) {
+    console.log('worker terminated with code ' + code);
+  });
+}

test/fixtures/cluster-preload.js

@@ -0,0 +1,3 @@
+var cluster = require('cluster');
+cluster.isMaster || process.exit(42 + cluster.worker.id); // +42 to distinguish
+// from exit(1) for other random reasons

test/parallel/test-preload.js

@@ -72,3 +72,11 @@ child_process.exec(nodeBinary + ' '
     if (err) throw err;
     assert.equal(stdout, 'A\nB\nhello\n');
   });
+
+child_process.exec(nodeBinary + ' '
+  + '--require ' + fixture('cluster-preload.js') + ' '
+  + fixture('cluster-preload-test.js'),
+  function(err, stdout, stderr) {
+    if (err) throw err;
+    assert.ok(/worker terminated with code 43/.test(stdout));
+  });