feature: add healthcheck

- add express npm to allow creation of health endpoint
- create health end pt as callback to livereload server listening state
- configure healthcheck in container
- allows true 'stack' operation since other services can query status

build/Dockerfile

@@ -45,13 +45,13 @@ ENV LR_DEBUG=true
 ENV LR_HTTPS=true
 ENV CERT_HOSTNAME=""
 
-# install node-livereload as node user then switch back to root user
+# install node-livereload and express as node user then switch back to root user
 USER node
 WORKDIR /home/node
 RUN mkdir -p .npm-global/bin .npm-global/lib \
     && npm config set fund false \
     && npm config set update-notifier false \
-    && npm install livereload --save
+    && npm install livereload express --save
 
 # copy scripts and fix-up all permissions
 USER root
@@ -63,6 +63,13 @@ RUN chown node:node /home/node/livereload.js \
     && chmod 755 /usr/local/bin/entrypoint.sh \
     && chmod 644 /etc/selfsigned.cnf
 
+HEALTHCHECK \
+    --interval=10s \
+    --timeout=5s \
+    --start-period=60s \
+    --retries=3 \
+    CMD wget --spider -T 3 -q localhost:3000/api/v1/health || exit 1
+
 # switch to node user, run entrypoint script by default
 USER node
 WORKDIR /home/node

build/livereload.js

@@ -1,7 +1,30 @@
 // implement node-livereload over an HTTPS connection
 
+// healthcheck function
+function healthcheck() {
+    const express = require('express');
+    const http = require('http');
+
+    const app = express();
+    const router = express.Router();
+
+    router.use((req, res, next) =>{
+        res.header('Access-Control-Allow-Methods', 'GET');
+        next();
+    });
+
+    router.get('/health', (req, res) =>{
+        res.status(200).send('Ok');
+    });
+
+    app.use('/api/v1', router);
+
+    const hServer = http.createServer(app);
+    hServer.listen(3000);
+}
+
 // load livereload module
-let livereload = require('livereload');
+const livereload = require('livereload');
 
 // set createServer options
 const fs = require('fs');
@@ -32,7 +55,7 @@ else {
 }
 
 // start server
-let server = livereload.createServer(options);
-server.watch('/watch')
+const lrServer = livereload.createServer(options, healthcheck);
+lrServer.watch('/watch')
 
 //#EOF