From 9058a59555416c0bead041b4e501941e8fa0faa7 Mon Sep 17 00:00:00 2001
From: ansuz <ansuz@transitiontech.ca>
Date: Fri, 27 Mar 2020 17:17:42 -0400
Subject: [PATCH] reassign db tasks if the responsible worker fails

---
 lib/workers/index.js      | 95 ++++++++++++++++++++++++++-------------
 www/common/common-util.js |  3 ++
 2 files changed, 66 insertions(+), 32 deletions(-)

diff --git a/lib/workers/index.js b/lib/workers/index.js
index 16282b202..5eeb5e285 100644
--- a/lib/workers/index.js
+++ b/lib/workers/index.js
@@ -115,14 +115,58 @@ Workers.initializeIndexWorkers = function (Env, config, _cb) {
         Log[level](label, info);
     };
 
+    var isWorker = function (value) {
+        return value && value.worker && typeof(value.worker.send) === 'function';
+    };
+
+    // pick ids that aren't already in use...
+    const guid = function () {
+        var id = Util.uid();
+        return response.expected(id)? guid(): id;
+    };
+
+    var workerIndex = 0;
+    var sendCommand = function (msg, _cb) {
+        console.log("SEND_COMMAND");
+        var cb = Util.once(Util.mkAsync(_cb));
+
+        workerIndex = (workerIndex + 1) % workers.length;
+        if (!isWorker(workers[workerIndex])) {
+            return void cb("NO_WORKERS");
+        }
+
+        var state = workers[workerIndex];
+
+        // XXX insert a queue here to prevent timeouts
+
+        const txid = guid();
+        msg.txid = txid;
+        msg.pid = PID;
+
+        // track which worker is doing which jobs
+        state.tasks[txid] = msg;
+        response.expect(txid, function (err, value) {
+            // clean up when you get a response
+            delete state[txid];
+            cb(err, value);
+        }, 60000);
+        state.worker.send(msg);
+    };
+
     const initWorker = function (worker, cb) {
         //console.log("initializing index worker");
-        const txid = Util.uid();
+        const txid = guid();
+
+        const state = {
+            worker: worker,
+            tasks: {},
+        };
+
         response.expect(txid, function (err) {
             if (err) { return void cb(err); }
             //console.log("worker initialized");
-            workers.push(worker);
-            cb();
+            workers.push(state);
+            cb(void 0, state);
         }, 15000);
 
         worker.send({
@@ -148,18 +192,28 @@ Workers.initializeIndexWorkers = function (Env, config, _cb) {
         });
 
         var substituteWorker = Util.once(function () {
-            // XXX reassign jobs delegated to failed workers
-            Env.Log.info("SUBSTITUTE_INDEX_WORKER", '');
-            var idx = workers.indexOf(worker);
+            Env.Log.info("SUBSTITUTE_DB_WORKER", '');
+            var idx = workers.indexOf(state);
             if (idx !== -1) {
                 workers.splice(idx, 1);
             }
+
+            Object.keys(state.tasks).forEach(function (txid) {
+                const cb = response.expectation(txid);
+                if (typeof(cb) !== 'function') { return; }
+                const task = state.tasks[txid];
+                if (!task && task.msg) { return; }
+                response.clear(txid);
+                Log.info('DB_WORKER_RESEND', task.msg);
+                sendCommand(task.msg, cb);
+            });
+
             var w = fork(DB_PATH);
-            initWorker(w, function (err) {
+            initWorker(w, function (err, state) {
                 if (err) {
                     throw new Error(err);
                 }
-                workers.push(w);
+                workers.push(state);
             });
         });
 
@@ -167,32 +221,12 @@ Workers.initializeIndexWorkers = function (Env, config, _cb) {
         worker.on('close', substituteWorker);
         worker.on('error', function (err) {
             substituteWorker();
-            Env.log.error("INDEX_WORKER_ERROR", {
+            Env.Log.error("DB_WORKER_ERROR", {
                 error: err,
             });
         });
     };
 
-    var workerIndex = 0;
-    var sendCommand = function (msg, _cb) {
-        var cb = Util.once(Util.mkAsync(_cb));
-
-        workerIndex = (workerIndex + 1) % workers.length;
-        if (workers.length === 0 ||
-            typeof(workers[workerIndex].send) !== 'function') {
-            return void cb("NO_WORKERS");
-        }
-
-        // XXX insert a queue here to prevent timeouts
-        // XXX track which worker is doing which jobs
-
-        const txid = Util.uid();
-        msg.txid = txid;
-        msg.pid = PID;
-        response.expect(txid, cb, 60000);
-        workers[workerIndex].send(msg);
-    };
-
     nThen(function (w) {
         OS.cpus().forEach(function () {
             initWorker(fork(DB_PATH), w(function (err) {
@@ -299,13 +333,10 @@ Workers.initializeIndexWorkers = function (Env, config, _cb) {
             }, cb);
         };
 
-        //console.log("index workers ready");
         cb(void 0);
     });
 };
 
-// XXX task expiration...
-
 Workers.initialize = function (Env, config, cb) {
     Workers.initializeValidationWorkers(Env);
     Workers.initializeIndexWorkers(Env, config, cb);
diff --git a/www/common/common-util.js b/www/common/common-util.js
index a1c35307f..cf7d5d97e 100644
--- a/www/common/common-util.js
+++ b/www/common/common-util.js
@@ -134,6 +134,9 @@
             expected: function (id) {
                 return Boolean(pending[id]);
             },
+            expectation: function (id) {
+                return pending[id];
+            },
             expect: expect,
             handle: handle,
         };