guard against several serverside typeErrors

and warn in cases where they would have occurred

lib/workers/index.js

@@ -82,6 +82,13 @@ Workers.initialize = function (Env, config, _cb) {
 
     var drained = true;
     var sendCommand = function (msg, _cb, opt) {
+        if (!_cb) {
+            return void Log.error('WORKER_COMMAND_MISSING_CB', {
+                msg: msg,
+                opt: opt,
+            });
+        }
+
         opt = opt || {};
         var index = getAvailableWorkerIndex();
 
@@ -95,7 +102,7 @@ Workers.initialize = function (Env, config, _cb) {
             });
             if (drained) {
                 drained = false;
-                Log.debug('WORKER_QUEUE_BACKLOG', {
+                Log.error('WORKER_QUEUE_BACKLOG', {
                     workers: workers.length,
                 });
             }
@@ -103,13 +110,6 @@ Workers.initialize = function (Env, config, _cb) {
             return;
         }
 
-        const txid = guid();
-        msg.txid = txid;
-        msg.pid = PID;
-
-        // track which worker is doing which jobs
-        state.tasks[txid] = msg;
-
         var cb = Util.once(Util.mkAsync(Util.both(_cb, function (err /*, value */) {
             if (err !== 'TIMEOUT') { return; }
             // in the event of a timeout the user will receive an error
@@ -120,6 +120,17 @@ Workers.initialize = function (Env, config, _cb) {
             delete state.tasks[txid];
         })));
 
+        if (!msg) {
+            return void cb('ESERVERERR');
+        }
+
+        const txid = guid();
+        msg.txid = txid;
+        msg.pid = PID;
+
+        // track which worker is doing which jobs
+        state.tasks[txid] = msg;
+
         // default to timing out affter 180s if no explicit timeout is passed
         var timeout = typeof(opt.timeout) !== 'undefined'? opt.timeout: 180000;
         response.expect(txid, cb, timeout);
@@ -153,6 +164,13 @@ Workers.initialize = function (Env, config, _cb) {
         }
 
         var nextMsg = queue.shift();
+
+        if (!nextMsg || !nextMsg.msg) {
+            return void Log.error('WORKER_QUEUE_EMPTY_MESSAGE', {
+                item: nextMsg,
+            });
+        }
+
 /*  `nextMsg` was at the top of the queue.
     We know that a job just finished and all of this code
     is synchronous, so calling `sendCommand` should take the worker
@@ -200,7 +218,7 @@ Workers.initialize = function (Env, config, _cb) {
                 const cb = response.expectation(txid);
                 if (typeof(cb) !== 'function') { return; }
                 const task = state.tasks[txid];
-                if (!task && task.msg) { return; }
+                if (!(task && task.msg)) { return; }
                 response.clear(txid);
                 Log.info('DB_WORKER_RESEND', task.msg);
                 sendCommand(task.msg, cb);