feat(k8s): gracefull shutdown

Author: rolandszoke

app/deployment.yaml

@@ -16,17 +16,29 @@ spec:
       - name: training
         image: training:v1
         imagePullPolicy: IfNotPresent
+        readinessProbe:
+          httpGet:
+            path: /healthz
+            port: 3000
+          initialDelaySeconds: 2
+          periodSeconds: 2
+          failureThreshold: 2
+          successThreshold: 1 # default
+          timeoutSeconds: 1 # default
         livenessProbe:
           httpGet:
             path: /healthz
             port: 3000
-          initialDelaySeconds: 30
-          timeoutSeconds: 1
+          initialDelaySeconds: 5
+          periodSeconds: 10
+          failureThreshold: 3 # default
+          successThreshold: 1 # default
+          timeoutSeconds: 1 # default
         ports:
         - containerPort: 3000
         env:
         - name: SHOULD_FAIL_WITHIN
-          value: "5000"
+          value: "300000"
         - name: REDIS_URI
           valueFrom:
             secretKeyRef:

app/index.js

@@ -1,19 +1,37 @@
 const express = require('express')
 const app = express()
 
-let healthy = true
-
+// READINESS_PROBE_DELAY = failureThreshold * periodSeconds * 1000
+const READINESS_PROBE_DELAY = 4000
+const state = { 
+  isShutdown: false,
+  healthy: true
+}
+console.log(process.pid)
 if(process.env.SHOULD_FAIL_WITHIN) {
-  setTimeout(() => { healthy = false }, process.env.SHOULD_FAIL_WITHIN)
+  setTimeout(() => { state.healthy = false }, process.env.SHOULD_FAIL_WITHIN)
 }
 
+process.on('SIGTERM', () => { 
+  state.isShutdown = true
+  setTimeout( function gracefulShutdown () {
+    server.close()
+    // db close
+    process.exit()
+  }, READINESS_PROBE_DELAY)
+})
+
 app.get('/', (req, res) => res.send('Hello World!'))
 app.get('/healthz', (req, res) => {
-  if(healthy) {
+  if (state.isShutdown) {
+    return res.send(503, 'Service is shutting down')
+  }
+
+  if(state.healthy) {
     return res.sendStatus(200)
   } else {
     return res.sendStatus(500)
   }
 })
 
-app.listen(3000, () => console.log('Example app listening on port 3000!'))
+const server = app.listen(3000, () => console.log('Example app listening on port 3000!'))