emit events on resize, restart, quit, quitHard

README.md

@@ -49,6 +49,13 @@ clusterMaster.quit()
 
 // not so graceful shutdown
 clusterMaster.quitHard()
+
+// listen to events to additional cleanup or shutdown
+clusterMaster.emitter()
+  .on('resize', function (clusterSize) { })
+  .on('restart', function () { })
+  .on('quit', function () { })
+  .on('quitHard', function () { });
 ```
 
 ## Methods
@@ -57,19 +64,29 @@ clusterMaster.quitHard()
 
 Set the cluster size to `n`.  This will disconnect extra nodes and/or
 spin up new nodes, as needed.  Done by default on restarts.
+Fires `resize` event with new clusterSize just before performing the
+resize.
 
 ### clusterMaster.restart(cb)
 
 One by one, shut down nodes and spin up new ones.  Callback is called
-when finished.
+when finished. Fires `restart` event just before performing restart.
 
 ### clusterMaster.quit()
 
 Gracefully shut down the worker nodes and then process.exit(0).
+Fires `quit` event just before performing the shutdown.
 
 ### clusterMaster.quitHard()
 
 Forcibly shut down the worker nodes and then process.exit(1).
+Fires `quitHard` event just before performing hard shut down.
+
+### clusterMaster.emitter()
+
+Retrieve the clusterMaster EventEmitter to be able to listen
+to clusterMaster events. This emitter is also returned from
+the original clusterMaster() constructor.
 
 ## Configs
 
@@ -89,3 +106,14 @@ The `exec`, `env`, `argv`, and `silent` configs are passed to the
   the parent.  Called in the context of the worker, so you can reply by
   looking at `this`.
 
+## Events
+
+clusterMaster emits events on clusterMaster.emitter() when its methods
+are called which allows you to respond and do additional cleanup right
+before the action is carried out.
+
+* `resize` - fired on clusterMaster.resize(n), listener ex: fn(clusterSize)
+* `restart` - fired on clusterMaster.restart(), listener ex: fn(oldWorkers)
+  `restartComplete` - fired when restart is completed
+* `quit` - fired on clusterMaster.quit()
+* `quitHard` - fired on clusterMaster.quitHard()

cluster-master.js

@@ -10,14 +10,17 @@ var cluster = require("cluster")
 , onmessage
 , repl = require('repl')
 , net = require('net')
+, EventEmitter = require('events').EventEmitter
+, masterEmitter = new EventEmitter()
 , fs = require('fs')
 , util = require('util')
 
 exports = module.exports = clusterMaster
-exports.restart = restart
-exports.resize = resize
-exports.quitHard = quitHard
-exports.quit = quit
+exports.emitter = emitter
+exports.restart = emitAndRestart
+exports.resize = emitAndResize
+exports.quitHard = emitAndQuitHard
+exports.quit = emitAndQuit
 
 var debugStreams = {}
 function debug () {
@@ -77,6 +80,8 @@ function clusterMaster (config) {
   // now make it the right size
   debug('resize and then setup repl')
   resize(setupRepl)
+
+  return masterEmitter
 }
 
 function select (field) {
@@ -126,9 +131,10 @@ function setupRepl () {
       })
       var context = {
         repl: r,
-        resize: resize,
-        restart: restart,
-        quit: quit,
+        resize: emitAndResize,
+        restart: emitAndRestart,
+        quit: emitAndQuit,
+        quitHard: emitAndQuitHard,
         cluster: cluster,
         get size () {
           return clusterSize
@@ -412,9 +418,9 @@ function quit () {
 
 function setupSignals () {
   try {
-    process.on("SIGHUP", restart)
-    process.on("SIGINT", quit)
-    process.on("SIGKILL", quitHard)
+    process.on("SIGHUP", emitAndRestart)
+    process.on("SIGINT", emitAndQuit)
+    process.on("SIGKILL", emitAndQuitHard)
   } catch (e) {
     // Must be on Windows, waaa-waaah.
   }
@@ -423,3 +429,40 @@ function setupSignals () {
     if (!quitting) quitHard()
   })
 }
+
+function emitter() {
+  return masterEmitter
+}
+
+function emitAndResize(n) {
+  masterEmitter.emit('resize', n)
+  process.nextTick(function () { resize(n) })
+}
+
+function emitAndRestart(cb) {
+  if (restarting) {
+    debug("Already restarting.  Cannot restart yet.")
+    return
+  }
+  var currentWorkers = Object.keys(cluster.workers).reduce(function (accum, k) {
+    accum[k] = { pid: cluster.workers[k].pid };
+    return accum;
+  }, {});
+  masterEmitter.emit('restart', currentWorkers);
+  process.nextTick(function () {
+    restart(function () {
+      masterEmitter.emit('restartComplete');
+      if (cb) cb();
+    });
+  });
+}
+
+function emitAndQuit() {
+  masterEmitter.emit('quit')
+  process.nextTick(function () { quit() })
+}
+
+function emitAndQuitHard() {
+  masterEmitter.emit('quitHard')
+  process.nextTick(function () { quitHard() })
+}