Support an extra shutdown signal

Beyond `SIGINT` and `SIGTERM`.

lib/throng.js

@@ -39,6 +39,7 @@ module.exports = function throng(options, startFunction) {
     cluster.on('exit', revive);
     emitter.once('shutdown', shutdown);
     var shutdownSignals = ['SIGINT', 'SIGTERM'];
+    if (opts.extraShutdownSignal) shutdownSignals.push(opts.extraShutdownSignal);
     shutdownSignals.forEach((signal) => {
       process.once(signal, () => emitter.emit('shutdown', signal));
     });

readme.md

@@ -68,11 +68,13 @@ Handling signals (for cleanup on a kill signal, for instance).
 
 ```js
 throng({
-  workers: 4,       // Number of workers (cpu count)
-  lifetime: 10000,  // ms to keep cluster alive (Infinity)
-  grace: 4000,      // ms grace period after worker SIGTERM (5000)
-  master: masterFn, // Function to call when starting the master process
-  start: startFn    // Function to call when starting the worker processes
+  workers: 4,                     // Number of workers (cpu count)
+  lifetime: 10000,                // ms to keep cluster alive (Infinity)
+  grace: 4000,                    // ms grace period after worker SIGTERM (5000)
+  master: masterFn,               // Function to call when starting the master process
+  start: startFn,                 // Function to call when starting the worker processes
+  extraShutdownSignal: 'SIGUSR2'  // Extra signal (beyond SIGINT & SIGTERM) in response
+                                  // to which to shut down the cluster
 });
 ```
 

test/fixtures/sigusr2.js

@@ -0,0 +1,17 @@
+'use strict';
+
+const throng = require('../../lib/throng');
+
+throng({
+  workers: 3,
+  lifetime: 500,
+  start: () => {
+    console.log('worker');
+
+    process.on('SIGTERM', function() {
+      console.log('exiting');
+      process.exit();
+    });
+  },
+  extraShutdownSignal: 'SIGUSR2'
+});

test/throng.test.js

@@ -15,6 +15,7 @@ const masterCmd = path.join(__dirname, 'fixtures', 'master');
 const gracefulCmd = path.join(__dirname, 'fixtures', 'graceful');
 const killCmd = path.join(__dirname, 'fixtures', 'kill');
 const infiniteCmd = path.join(__dirname, 'fixtures', 'infinite');
+const sigusr2Cmd = path.join(__dirname, 'fixtures', 'sigusr2');
 
 describe('throng()', function() {
 
@@ -173,6 +174,20 @@ describe('throng()', function() {
       });
     });
 
+    describe('with custom signal handling', function() {
+      before(function(done) {
+        var child = run(sigusr2Cmd, this, done);
+        setTimeout(function() { child.kill('SIGUSR2'); }, 750);
+      });
+      it('allows the workers to shut down', function() {
+        var exits = this.stdout.match(/exiting/g).length;
+        assert.equal(exits, 3);
+      });
+      it('exits with SIGUSR2', function() {
+        assert.equal(this.signal, 'SIGUSR2');
+      });
+    });
+
   });
 
 });