log child process ids in the event of an RPC timeout

lib/workers/index.js

@@ -139,6 +139,9 @@ Workers.initialize = function (Env, config, _cb) {
 
         msg.txid = txid;
         msg.pid = PID;
+        // include the relevant worker process id in messages so that it will be logged
+        // in the event that the message times out or fails in other ways.
+        msg.worker = state.pid;
 
         // track which worker is doing which jobs
         state.tasks[txid] = msg;
@@ -201,6 +204,7 @@ Workers.initialize = function (Env, config, _cb) {
         const state = {
             worker: worker,
             tasks: {},
+            pid: worker.pid, // store the child process's id in an easily accessible location
         };
 
         response.expect(txid, function (err) {