chore(#9585): teach Sentinel sign language

sentinel/server.js

@@ -35,20 +35,26 @@ const waitForApi = () => new Promise(resolve => {
 });
 
 logger.info('Running server checks...');
-serverChecks
-  .check(environment.couchUrl)
-  .then(waitForApi)
-  .then(() => {
-    // Even requiring this boots translations, so has to be required after
-    // api has booted
+
+(async () => {
+  try {
+    await serverChecks.check(environment.couchUrl);
+    await waitForApi();
+
     const config = require('./src/config');
-    return config.init().then(() => {
-      require('./src/schedule').init();
-      logger.info('startup complete.');
-    });
-  })
-  .catch(err => {
-    logger.error('Fatal error intialising sentinel');
+    await config.init();
+
+    const schedule = require('./src/schedule');
+    schedule.init();
+
+    logger.info('startup complete.');
+
+    const processHooks = require('./src/process-hooks');
+    processHooks.init();
+
+  } catch (err) {
+    logger.error('Fatal error initialising sentinel');
     logger.error('%o', err);
     process.exit(1);
-  });
+  }
+})();

sentinel/src/lib/feed.js

@@ -15,6 +15,7 @@ const MAX_QUEUE_SIZE = 100;
 
 let request;
 let processed = 0;
+let processing;
 
 const enqueue = change => changeQueue.push(change);
 
@@ -100,33 +101,32 @@ changeQueue.drain(() => {
   resumeProcessing();
 });
 
+/**
+ * Start listening from the last processed seq. Will restart
+ * automatically on error.
+ */
 const listen = () => {
+  processing = true;
   changeQueue.resume();
   return resumeProcessing();
 };
 
-module.exports = {
+/**
+ * Stops listening for changes. Must be restarted manually
+ * by calling listen.
+ */
+const cancel =  () => {
+  processing = false;
+  changeQueue.pause();
+  if (request) {
+    request.cancel && request.cancel();
+    request = null;
+  }
+};
 
-  /**
-   * Start listening from the last processed seq. Will restart
-   * automatically on error.
-   */
+module.exports = {
   listen,
+  cancel,
 
-  /**
-   * Stops listening for changes. Must be restarted manually
-   * by calling listen.
-   */
-  cancel: () => {
-    changeQueue.pause();
-    if (request) {
-      request.cancel && request.cancel();
-      request = null;
-    }
-  },
-
-  // exposed for testing
-  _changeQueue: changeQueue,
-  _transitionsLib: transitionsLib,
-  _enqueue: enqueue,
+  toggle: () => processing ? cancel() : listen()
 };

sentinel/src/process-hooks.js

@@ -0,0 +1,13 @@
+const feed = require('./lib/feed');
+const schedule = require('./schedule');
+
+module.exports = {
+  init: () => {
+    process.on('SIGUSR1', () => {
+      feed.toggle();
+    });
+    process.on('SIGCONT', () => {
+      schedule.runTasks();
+    });
+  }
+};

sentinel/src/schedule/index.js

@@ -72,3 +72,4 @@ exports.init = () => {
   runTasks();
   interval = setInterval(runTasks, RUN_EVERY_MS);
 };
+exports.runTasks = runTasks;

sentinel/src/transitions.js

@@ -20,8 +20,5 @@ module.exports = {
   /**
    * Loads the transitions and starts watching for db changes.
    */
-  loadTransitions: loadTransitions,
-
-  // exposed for testing
-  _transitionsLib: transitionsLib,
+  loadTransitions,
 };