disable worker task queueing and address a probable memory leak

lib/workers/index.js

@@ -8,7 +8,7 @@ const Workers = module.exports;
 const PID = process.pid;
 
 const DB_PATH = 'lib/workers/db-worker';
-const MAX_JOBS = 8;
+const MAX_JOBS = 16;
 
 Workers.initialize = function (Env, config, _cb) {
     var cb = Util.once(Util.mkAsync(_cb));
@@ -35,6 +35,11 @@ Workers.initialize = function (Env, config, _cb) {
         return response.expected(id)? guid(): id;
     };
 
+    const countWorkerTasks = function (/* index */) {
+        return 0; // XXX this disables all queueing until it can be proven correct
+        //return Object.keys(workers[index].tasks || {}).length;
+    };
+
     var workerOffset = -1;
     var queue = [];
     var getAvailableWorkerIndex = function () {
@@ -67,7 +72,8 @@ Workers.initialize = function (Env, config, _cb) {
     but this is a relatively easy way to make sure it's always up to date.
     We'll see how it performs in practice before optimizing.
 */
-            if (workers[temp] && Object.keys(workers[temp].tasks || {}).length < MAX_JOBS) {
+
+            if (workers[temp] && countWorkerTasks(temp) <= MAX_JOBS) {
                 return temp;
             }
         }
@@ -96,15 +102,23 @@ Workers.initialize = function (Env, config, _cb) {
             return;
         }
 
-        var cb = Util.once(Util.mkAsync(_cb));
-
         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
+            // but the state used to resend a query in the event of a worker crash
+            // won't be cleared. This also leaks a slot that could be used to keep
+            // an upper bound on the amount of parallelism for any given worker.
+            // if you run out of slots then the worker locks up.
+            delete state.tasks[txid];
+        })));
+
         response.expect(txid, cb, 180000);
         state.worker.send(msg);
     };