From 84ab47d6e5e02ac81958ec0dd5a662cf202ed9e1 Mon Sep 17 00:00:00 2001
From: Gareth Jones <gareth.jones@shinetech.com>
Date: Tue, 18 Jul 2017 22:42:06 +1000
Subject: [PATCH] feat(pm2): got pm2 working, needs tests

---
 lib/configuration.js         |  5 ++++-
 lib/log4js.js                | 41 +++++++++++++++++++++++-------------
 test/tap/pm2-support-test.js | 10 +++++++++
 3 files changed, 40 insertions(+), 16 deletions(-)
 create mode 100644 test/tap/pm2-support-test.js

diff --git a/lib/configuration.js b/lib/configuration.js
index 71cb484..2339117 100644
--- a/lib/configuration.js
+++ b/lib/configuration.js
@@ -76,7 +76,7 @@ class Configuration {
       debug(`DEPRECATION: Appender ${config.type} exports a shutdown function.`);
     }
 
-    if (cluster.isMaster) {
+    if (cluster.isMaster || (this.pm2 && process.env[this.pm2InstanceVar] === '0')) {
       return appenderModule.configure(
         config,
         layouts,
@@ -195,6 +195,9 @@ class Configuration {
     this.throwExceptionIf(not(anObject(candidate.appenders)), 'must have a property "appenders" of type object.');
     this.throwExceptionIf(not(anObject(candidate.categories)), 'must have a property "categories" of type object.');
 
+    this.pm2 = this.candidate.pm2;
+    this.pm2InstanceVar = this.candidate.pm2InstanceVar || 'NODE_APP_INSTANCE';
+
     this.levels = candidate.levels;
     this.appenders = candidate.appenders;
     this.categories = candidate.categories;
diff --git a/lib/log4js.js b/lib/log4js.js
index 91b147e..2184863 100644
--- a/lib/log4js.js
+++ b/lib/log4js.js
@@ -139,7 +139,7 @@ function sendLogEventToAppender(logEvent) {
 
 function workerDispatch(logEvent) {
   debug(`sending message to master from worker ${process.pid}`);
-  process.send({ type: '::log4js-message', event: serialise(logEvent) });
+  process.send({ topic: 'log4js:message', data: serialise(logEvent) });
 }
 
 /**
@@ -162,6 +162,21 @@ function loadConfigurationFile(filename) {
   return filename;
 }
 
+// in a multi-process node environment, worker loggers will use
+// process.send
+const receiver = (worker, message) => {
+  // prior to node v6, the worker parameter was not passed (args were message, handle)
+  debug('cluster message received from worker ', worker, ': ', message);
+  if (worker.topic && worker.data) {
+    message = worker;
+    worker = undefined;
+  }
+  if (message && message.topic && message.topic === 'log4js:message') {
+    debug('received message: ', message.data);
+    sendLogEventToAppender(deserialise(message.data));
+  }
+};
+
 function configure(configurationFileOrObject) {
   let configObject = configurationFileOrObject;
 
@@ -175,6 +190,15 @@ function configure(configurationFileOrObject) {
   Logger = loggerModule.Logger;
   LoggingEvent = loggerModule.LoggingEvent;
   module.exports.connectLogger = connectModule(config.levels).connectLogger;
+
+  // PM2 cluster support
+  // PM2 runs everything as workers - install pm2-intercom for this to work.
+  // we only want one of the app instances to write logs
+  if (config.pm2 && process.env[config.pm2InstanceVar] === '0') {
+    debug('listening for PM2 broadcast messages');
+    process.on('message', receiver);
+  }
+
   enabled = true;
 }
 
@@ -236,20 +260,7 @@ const log4js = {
 
 module.exports = log4js;
 
-// in a multi-process node environment, worker loggers will use
-// process.send
-cluster.on('message', (worker, message) => {
-  // prior to node v6, the worker parameter was not passed (args were message, handle)
-  debug('cluster message received from worker ', worker, ': ', message);
-  if (worker.type && worker.event) {
-    message = worker;
-    worker = undefined;
-  }
-  if (message && message.type && message.type === '::log4js-message') {
-    debug('received message: ', message.event);
-    sendLogEventToAppender(deserialise(message.event));
-  }
-});
+cluster.on('message', receiver);
 
 // set ourselves up
 configure(process.env.LOG4JS_CONFIG || defaultConfig);
diff --git a/test/tap/pm2-support-test.js b/test/tap/pm2-support-test.js
new file mode 100644
index 0000000..863fd74
--- /dev/null
+++ b/test/tap/pm2-support-test.js
@@ -0,0 +1,10 @@
+'use strict';
+
+const test = require('tap').test;
+
+test('PM2 Cluster support', (batch) => {
+  batch.test('should listen for messages if pm2 support enabled');
+  batch.test('should write messages on NODE_APP_INSTANCE - 0');
+  batch.test('should send messages with the correct format');
+  batch.end();
+});