Issue/58 (#59)

* feature: provide a range of health check ports, HTTP_PORT to HTTP_PORT_MAX, bind to first available

* feature: provide a range of aws sns ports, AWS_SNS_PORT to AWS_SNS_PORT_MAX, bind to first available

* AWS SNS port range 3010-3019

lib/aws-sns-lifecycle.js

@@ -1,7 +1,7 @@
 const Emitter = require('events');
 const bent = require('bent');
 const assert = require('assert');
-const PORT = process.env.AWS_SNS_PORT || 3001;
+const PORT = process.env.AWS_SNS_PORT || 3010;
 const {LifeCycleEvents} = require('./constants');
 const express = require('express');
 const app = express();
@@ -21,6 +21,26 @@ class SnsNotifier extends Emitter {
 
     this.logger = logger;
   }
+  _doListen(logger, app, port, resolve) {
+    return app.listen(port, () => {
+      this.snsEndpoint = `http://${this.publicIp}:${port}`;
+      logger.info(`SNS lifecycle server listening on http://localhost:${port}`);
+      resolve(app);
+    });
+  }
+
+  _handleErrors(logger, app, resolve, reject, e) {
+    if (e.code === 'EADDRINUSE' &&
+      process.env.AWS_SNS_PORT_MAX &&
+      e.port < process.env.AWS_SNS_PORT_MAX) {
+
+      logger.info(`SNS lifecycle server failed to bind port on ${e.port}, will try next port`);
+      const server = this._doListen(logger, app, ++e.port, resolve);
+      server.on('error', this._handleErrors.bind(null, logger, app, resolve, reject));
+      return;
+    }
+    reject(e);
+  }
 
   async _handlePost(req, res) {
     try {
@@ -45,6 +65,7 @@ class SnsNotifier extends Emitter {
           }, 'response from SNS SubscribeURL');
           const data = await this.describeInstance();
           this.lifecycleState = data.AutoScalingInstances[0].LifecycleState;
+          this.emit('SubscriptionConfirmation', {publicIp: this.publicIp});
           break;
 
         case 'Notification':
@@ -80,14 +101,12 @@ class SnsNotifier extends Emitter {
 
   async init() {
     try {
-      this.logger.info('SnsNotifier: retrieving instance data');
+      this.logger.debug('SnsNotifier: retrieving instance data');
       this.instanceId = await getString('http://169.254.169.254/latest/meta-data/instance-id');
       this.publicIp = await getString('http://169.254.169.254/latest/meta-data/public-ipv4');
-      this.snsEndpoint = `http://${this.publicIp}:${PORT}`;
       this.logger.info({
         instanceId: this.instanceId,
-        publicIp: this.publicIp,
-        snsEndpoint: this.snsEndpoint
+        publicIp: this.publicIp
       }, 'retrieved AWS instance data');
 
       // start listening
@@ -99,7 +118,10 @@ class SnsNotifier extends Emitter {
         this.logger.error(err, 'burped error');
         res.status(err.status || 500).json({msg: err.message});
       });
-      app.listen(PORT);
+      return new Promise((resolve, reject) => {
+        const server = this._doListen(this.logger, app, PORT, resolve);
+        server.on('error', this._handleErrors.bind(null, this.logger, app, resolve, reject));
+      });
 
     } catch (err) {
       this.logger.error({err}, 'Error retrieving AWS instance metadata');

lib/utils.js

@@ -71,6 +71,26 @@ const  systemHealth = async(redisClient, ping, getCount) => {
   return getCount();
 };
 
+const doListen = (logger, app, port, resolve) => {
+  return app.listen(port, () => {
+    logger.info(`Health check server listening on http://localhost:${port}`);
+    resolve(app);
+  });
+};
+const handleErrors = (logger, app, resolve, reject, e) => {
+  if (e.code === 'EADDRINUSE' &&
+    process.env.HTTP_PORT_MAX &&
+    e.port < process.env.HTTP_PORT_MAX) {
+
+    logger.info(`Health check server failed to bind port on ${e.port}, will try next port`);
+    const server = doListen(logger, app, ++e.port, resolve);
+    server.on('error', handleErrors.bind(null, logger, app, resolve, reject));
+    return;
+  }
+  reject(e);
+};
+
+
 const createHealthCheckApp = (port, logger) => {
   const express = require('express');
   const app = express();
@@ -78,11 +98,9 @@ const createHealthCheckApp = (port, logger) => {
   app.use(express.urlencoded({ extended: true }));
   app.use(express.json());
 
-  return new Promise((resolve) => {
-    app.listen(port, () => {
-      logger.info(`Health check server started at http://localhost:${port}`);
-      resolve(app);
-    });
+  return new Promise((resolve, reject) => {
+    const server = doListen(logger, app, port, resolve);
+    server.on('error', handleErrors.bind(null, logger, app, resolve, reject));
   });
 };