Updated packages, config reading and adding command execution on failure

.eslintrc.json

@@ -0,0 +1,13 @@
+{
+  "extends": "strongloop",
+  "rules": {
+    "max-len": [2, 120, 8]
+  },
+  "env": {
+    "node": true,
+    "es6": true
+  },
+  "parserOptions": {
+    "ecmaVersion": 2018
+  }
+}

README.md

@@ -1,6 +1,8 @@
 # Simple remote port monitor tool
 
-A simple configurable tool to monitor remote ports and notify if connectivity fails. **Discord channel** as well as **Email** notifications are currently available.
+A simple configurable tool to monitor remote ports and notify if connectivity fails. If the application is running in same server as the service, a command can be configured to be executed on connectivity check failure.
+
+**Discord channel** as well as **Email** notifications are currently available.
 
 ## Requirement
 
@@ -13,7 +15,7 @@ A simple configurable tool to monitor remote ports and notify if connectivity fa
 - Install latest LTS version NodeJS (Refer https://nodejs.org).
 - Clone this repository.
 - Run `npm install` command in the project directory to install all dependencies.
-- Create the file `config.json` and copy all contents from `config_example.json`. Update configuration as per your requirements.
+- Create the file `development.json` or `production.json` based upon environment to override default config.
 - Run `node app.js` command in the project directory to start the monitoring for testing purpose.
 - Install PM2 (Refer https://pm2.keymetrics.io/) and run the command `pm2 start app.js` in the project directory to run it as a background service in your server.
 
@@ -27,10 +29,11 @@ A simple configurable tool to monitor remote ports and notify if connectivity fa
 | discord_webhooks   | Array of Discord webhooks to which notification will be sent            |
 | notify_emails      | Array of emails to which notification will be sent                      |
 | smtp_transport     | SMTP server details using which tool will send emails                   |
+| message_strings    | Holds text that is sent when a service is down                          |
 
 ### Example Configuration
 
-This is a full config example with discord webhook and SMTP configurations included for reference purpose
+This is a full config example with restart command, discord webhook and SMTP configurations included for reference purpose
 
 ```
 {
@@ -40,7 +43,8 @@ This is a full config example with discord webhook and SMTP configurations inclu
   "services": [{
     "name": "My local web server",
     "host": "127.0.0.1",
-    "port": 80
+    "port": 80,
+    "command": "sudo service apache2 restart"
   }],
   "discord_webhooks": [
     "https://discordapp.com/api/webhooks/{id}/{token}"

app.js

@@ -1,13 +1,15 @@
-'use strict';
+/**
+ * Simple port monitor and restart tool
+ */
 
 const axios = require('axios');
-const config = require('./config.json');
+const config = require('config');
 const net = require('net');
 const nodemailer = require('nodemailer');
+const { exec } = require('child_process');
 
-
-const MILISECONDS_TO_SECONDS_FACTOR = 1000;
-const DEFAULT_TIMEOUT_IN_SECONDS = 10000;
+const MILLISECONDS_TO_SECONDS_FACTOR = 1000;
+const DEFAULT_TIMEOUT_IN_SECONDS = 10;
 
 var notificationLog = {};
 try {
@@ -29,82 +31,99 @@ try {
   console.log(e);
 }
 
-// TODO: Make sure config is valid
-
+// Start monitoring process
 function startMonitoring() {
   console.log('Starting monitoring service...');
   if (!config['services'] || !config['services'].length) {
     console.log('No services have been configured to be monitored!');
   } else {
     checkAndNotifyAllServices();
-    setInterval(checkAndNotifyAllServices, config['monitor_interval'] * MILISECONDS_TO_SECONDS_FACTOR);
+    setInterval(checkAndNotifyAllServices, config['monitor_interval'] * MILLISECONDS_TO_SECONDS_FACTOR);
   }
 }
 
+// Function thats called at given interval which checks services and notifies if down
 function checkAndNotifyAllServices() {
   config['services'].forEach(service => {
     if (service.host && service.port && service.name) {
       console.log(`Checking ${service.name} connectivity...`);
-      checkConnection(service.name, service.host, service.port)
+      checkConnection(service)
         .then(result => {
           console.log(`${result.name} connectivity check succeeded!`);
           if (notificationLog[result.name]) {
             delete notificationLog[result.name];
           }
         }).catch(result => {
           console.log(`${result.name} connectivity check failed!`);
+          if (result.command) {
+            executeCommand(result.command);
+          }
           notifyFailure(result);
         });
     }
   });
 }
 
-function notifyFailure(data) {
+// Notify failure
+function notifyFailure({name, host, port, command}) {
   let currentTime = process.hrtime();
   // Do not notify if interval has not reached
-  const notification = notificationLog[data.name];
+  const notification = notificationLog[name];
   if (notification && currentTime[0] - notification < config['notify_interval']) {
     return;
   }
-  notificationLog[data.name] = currentTime[0];
 
-  const notificationMsg = `@here ${data.name} service with host ${data.host}\
- and port ${data.port} has gone down!`;
+  // Set current time as last notification time
+  notificationLog[name] = currentTime[0];
+
+  // Generate failure message
+  let notificationMsg;
+  if (command) {
+    notificationMsg = renderTemplate(config['message_strings']['failure_with_command'], {name, host, port, command});
+  } else {
+    notificationMsg = renderTemplate(config['message_strings']['failure'], {name, host, port});
+  }
+
+  // Discord notification
   if (config['discord_webhooks'] && config['discord_webhooks'].length) {
     config['discord_webhooks'].forEach(webhook => discordNotification(webhook, notificationMsg));
   }
 
+  // Email notification
   if (config['notify_emails'] && config['notify_emails'].length) {
     config['notify_emails'].forEach(email => emailNotification(email, notificationMsg, notificationMsg));
   }
 }
 
-async function discordNotification(webhookUrl, content) {
+// Discord webhook notification
+function discordNotification(webhookUrl, content) {
   try {
-    await axios.post(webhookUrl, {
-      content: content
+    axios.post(webhookUrl, {
+      content: content,
     });
   } catch (err) {
     console.log(err);
   }
 }
 
+// SMTP email notification
 function emailNotification(toAddress, subject, body) {
   if (config['smtp_transport'] && config['smtp_transport']['host']) {
     let transporter = nodemailer.createTransport(config['smtp_transport']);
     transporter.sendMail({
       from: config['smtp_transport']['auth']['user'],
       to: toAddress,
       subject: subject,
-      text: body
+      text: body,
     });
   }
 }
 
-function checkConnection(serviceName, host, port) {
+// Checks whether the service port is open by trying to connect to it
+function checkConnection({name, host, port, command}) {
   return new Promise((resolve, reject) => {
     const connectionTimeout = config['connection_timeout'];
-    const timeout = connectionTimeout ? connectionTimeout * MILISECONDS_TO_SECONDS_FACTOR :
+    const timeout = connectionTimeout ? connectionTimeout * MILLISECONDS_TO_SECONDS_FACTOR :
       DEFAULT_TIMEOUT_IN_SECONDS;
     const timer = setTimeout(() => {
       reject('timeout');
@@ -113,20 +132,60 @@ function checkConnection(serviceName, host, port) {
     const socket = net.createConnection(port, host, () => {
       clearTimeout(timer);
       resolve({
-        name: serviceName,
-        host: host,
-        port: port
+        name,
+        host,
+        port,
       });
       socket.end();
     });
-    socket.on('error', (err) => {
+    socket.on('error', (error) => {
       clearTimeout(timer);
       reject({
-        name: serviceName,
-        host: host,
-        port: port,
-        error: err
+        name,
+        host,
+        port,
+        error,
+        command,
       });
     });
   });
 }
+
+// Executes failure command
+function executeCommand(command) {
+  exec(command, (error, stdout, stderr) => {
+    if (error) {
+      console.log(`${command} error: ${error.message}`);
+      return;
+    }
+    if (stderr) {
+      console.log(`${command} stderr: ${stderr}`);
+      return;
+    }
+    console.log(`${command} stdout: ${stdout}`);
+  });
+}
+
+// Ref: https://stackoverflow.com/questions/29182244/convert-a-string-to-a-template-string
+function Prop(obj, is, value) {
+  if (typeof is === 'string')
+    is = is.split('.');
+  if (is.length === 1 && value !== undefined)
+    // eslint-disable-next-line no-return-assign
+    return obj[is[0]] = value;
+  else if (is.length === 0)
+    return obj;
+  else {
+    var prop = is.shift();
+    // Forge a path of nested objects if there is a value to set
+    if (value !== undefined && obj[prop] === undefined) obj[prop] = {};
+    return Prop(obj[prop], is, value);
+  }
+}
+
+// Ref: https://stackoverflow.com/questions/29182244/convert-a-string-to-a-template-string
+function renderTemplate(str, obj) {
+  return str.replace(/\$\{(.+?)\}/g, (match, p1) => {
+    return Prop(obj, p1);
+  });
+}

config/.gitignore

@@ -0,0 +1,3 @@
+*
+!.gitignore
+!default.json

config/default.json

@@ -0,0 +1,13 @@
+{
+  "notify_interval": 900,
+  "monitor_interval": 60,
+  "connection_timeout": 30,
+  "services": {},
+  "discord_webhooks": [],
+  "notify_emails": [],
+  "smtp_transport": {},
+  "message_strings": {
+    "failure": "**${name}** service with host **${host}** and port **${port}** has gone down!",
+    "failure_with_command": "**${name}** service with host **${host}** and port **${port}** has gone down. **${command}** was executed!"
+  }
+}