cluster.worker.id not present when using preload module (-r)

[megastef]

I'm using for logging for each forked worker the property worker.id - this works fine for node 0.10,0.12 and io.js up to 1.5 - in 1.6.2, only when I use the new -r / preload option to preload the logging module I get following error:

  postfix = '.worker-' + cluster.worker.id 
                                       ^
  TypeError: Cannot read property 'id' of undefined

How can this happen?

The related source code:

if (!cluster.isMaster)
    postfix = '.worker-' + cluster.worker.id 

https://nodejs.org/api/cluster.html#cluster_cluster_worker
https://nodejs.org/api/cluster.html#cluster_worker_id

[meandmycode]

Possibly ping @ofrobots

[ofrobots]

@megastef Do you have a reduced test-case I can try? I just tried this: https://gist.github.com/ofrobots/81a76e326a293ab568b4 but that doesn't reproduce the issue.

[megastef]

Ok, thanks - I will try to reproduce it - and create test case (need to check if was on ARM or x86 as well).

[megastef]

@ofrobots Added a comment to your gist to reproduce it.

[megastef]

BTW: This is the real use case. I load our monitoring agent via -r - normally it would need to modify source code to load it with "var spm = require('spm-agent-nodejs')"
The result when I use -r is here: https://gist.github.com/megastef/0dd384e09ec0465a4fcb

The idea was to write no own wrapper/proxy script by using -r option. It would allow to load monitoring/instrumentation functions without modification of original source-code.

[ofrobots]

The problem was due to the fact that the preload modules were getting executed before the code in node.js that is supposed to call cluster._setupWorker. The following patch fixes the problem.

diff --git a/src/node.js b/src/node.js
index 6346529..095b4c6 100644
--- a/src/node.js
+++ b/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 &&

I will submit a PR. Thanks for reporting!

[megastef]

1000 thx for fixing :)

[bnoordhuis]

Fixed by b6e22c4.