Introducing health API call. And add the health check to Dockerfile

Dockerfile

@@ -11,4 +11,8 @@ RUN npm install
 COPY . .
 
 EXPOSE 3010
+
+HEALTHCHECK --interval=30s --timeout=12s --start-period=25s \
+  CMD node healthcheck.js
+
 CMD ["npm", "start"]

healthcheck.js

+const http = require('http')
+
+const options = {
+  host: 'localhost',
+  port: '3010',
+  path: '/health',
+  timeout: 2000
+}
+
+const request = http.request(options, (res) => {
+  console.log(`STATUS: ${res.statusCode}`)
+  if (res.statusCode === 200) {
+    process.exit(0)
+  } else {
+    process.exit(1)
+  }
+})
+
+request.on('error', (err) => {
+  console.log('ERROR: ' + err.message)
+  process.exit(1)
+})
+
+request.end()

src/communicate.js

@@ -9,6 +9,7 @@ class Communicate {
   constructor (bot, botChatID) {
     this.bot = bot
     this.botChatID = botChatID
+    this.fatalError = false
     this.sendMessageOptions = { parse_mode: 'markdown', disable_web_page_preview: true }
     // Notify channel about Bot booting-up (commented-out for now)
     this.sendTelegramMessage('(Re)starting-up Bot... 🤓')
@@ -83,9 +84,18 @@ class Communicate {
 
     this.bot.sendMessage(this.botChatID, message, this.sendMessageOptions).catch(error => {
       console.log('ERROR: Could not send Telegram message: "' + message + '", due to error: ' + error.message)
+      this.fatalError = true
     })
   }
 
+  /**
+   * Retrieve fatal error state
+   * @returns true if an fatal error ever occurred. Otherwise false.
+   */
+  isError () {
+    return this.fatalError
+  }
+
   /**
    * Read content from file
    * @param {String} fileName file name

src/index.js

@@ -36,8 +36,15 @@ const bot = new TelegramBot(cfg.telegram_settings.bot_token)
 // Inform the Telegram servers of the new webhook url
 bot.setWebHook(`${cfg.telegram_settings.public_url}/bot${TELEGRAM_SECRET_HASH}`)
 
-const app = express()
+// Create API Fetcher, data processor and communication instances
+const fetcher = new Fetcher(cfg.exchange_settings)
+const dataProcessor = new DataProcessor(
+  cfg.tickers.warmup_period,
+  cfg.tickers.data_period,
+  cfg.tickers.indicators)
+const comm = new Communicate(bot, cfg.telegram_settings.chat_id)
 
+const app = express()
 app.use(express.json())
 app.use(express.urlencoded({ extended: false }))
 
@@ -55,9 +62,11 @@ app.get(`/test_api/${TEST_API_SECRET_HASH}/crypto`, (req, res) => {
   res.send('OK')
 })
 
-// Start Express Server
-app.listen(port, host, () => {
-  console.log(`INFO: Crypto Exchange Bot v${version} is now running on ${host} on port ${port}.`)
+app.get('/health', (req, res) => {
+  // Check if there are any issues with the communication layer
+  const isError = comm.isError()
+  const statusCode = (isError) ? 500 : 200
+  res.status(statusCode).json({ health_ok: !isError })
 })
 
 // Simple ping command
@@ -75,13 +84,10 @@ bot.sendMessage = (a, b, c) => {
   })
 } */
 
-// Create API Fetcher, data processor and communication instances
-const fetcher = new Fetcher(cfg.exchange_settings)
-const dataProcessor = new DataProcessor(
-  cfg.tickers.warmup_period,
-  cfg.tickers.data_period,
-  cfg.tickers.indicators)
-const comm = new Communicate(bot, cfg.telegram_settings.chat_id)
+// Start Express Server
+app.listen(port, host, () => {
+  console.log(`INFO: Crypto Exchange Bot v${version} is now running on ${host} on port ${port}.`)
+})
 
 /**
  * Due to the 8 API/min rate limit, we need to call the API with time-outs