feat: add health probes for kubernetes

charts/app/templates/deployment-server.yaml

@@ -39,6 +39,17 @@ spec:
             {{- with .Values.app.pods.extraEnvs }}
             {{- toYaml . | nindent 12 }}
             {{- end }}
+          livenessProbe:
+            httpGet:
+              port: 3000
+              path: /healthChecks/live
+              scheme: HTTP
+          readinessProbe:
+            initialDelaySeconds: 1
+            httpGet:
+              port: 3000
+              path: /healthChecks/ready
+              scheme: HTTP
           ports:
             - name: http
               containerPort: 3000

src/server/core/commands.ts

@@ -3,6 +3,7 @@ import { getDatabaseContext, migrate } from '../database';
 import { setup as startWorker } from '../queues';
 import config from './config';
 import createWebServer from './createWebServer';
+import { updateStatus, HealthStatus } from './health';
 import { initializeSentry } from './sentry';
 
 export const startServerCommand = async () => {
@@ -11,13 +12,19 @@ export const startServerCommand = async () => {
     initializeSentry({ app: expressServer });
 
     httpServer.listen(config.port, () => {
+        updateStatus(HealthStatus.Running);
         console.info(chalk.cyan('Server listening'));
     });
 
-    return () =>
-        new Promise(resolve => {
-            httpServer.close(resolve);
-        });
+    return () => {
+        updateStatus(HealthStatus.Stopping);
+
+        return new Promise(resolve => {
+            setTimeout(() => {
+                httpServer.close(resolve);
+            }, 10000);
+        }).then(() => updateStatus(HealthStatus.Stopped));
+    };
 };
 
 export const startWorkerCommand = () => {

src/server/core/createWebServer.ts

@@ -11,6 +11,7 @@ import { SubscriptionServer } from 'subscriptions-transport-ws';
 import schema from '../schema';
 import createContext, { Context, RootDocument } from '../schema/context';
 import config from './config';
+import { createHealthRouter } from './health';
 import setupPrometheusMetrics, { ApolloMetricsPlugin } from './prometheus';
 import { expressRateLimiter } from './rateLimiter';
 import renderApplication from './renderApplication';
@@ -125,6 +126,9 @@ const createWebServer = async (): Promise<WebServerCreation> => {
     // update cache policy
     expressServer.use(disableCaching);
 
+    // health endpoints
+    expressServer.use('/healthChecks', createHealthRouter());
+
     // serve graphql API
     expressServer.use(
         '/graphql',

src/server/core/health.ts

@@ -0,0 +1,65 @@
+import { Router } from 'express';
+
+export enum HealthStatus {
+    Starting,
+    Running,
+    Stopping,
+    Stopped,
+}
+
+let currentStatus = HealthStatus.Starting;
+
+const statusLabels = new Map<number, string>([
+    [HealthStatus.Starting, 'Starting'],
+    [HealthStatus.Running, 'Up'],
+    [HealthStatus.Stopped, 'Stopped'],
+    [HealthStatus.Stopping, 'Stopping'],
+]);
+
+export const createHealthRouter = () => {
+    // @ts-ignore
+    const router = new Router();
+
+    router.get('/ready', (req, res) => {
+        switch (currentStatus) {
+            case HealthStatus.Running:
+                res.status(200).send(statusLabels[HealthStatus.Running]);
+                break;
+
+            default:
+                res.status(503).send(statusLabels[currentStatus]);
+                break;
+        }
+    });
+
+    router.get('/live', (req, res) => {
+        switch (currentStatus) {
+            case HealthStatus.Starting:
+            case HealthStatus.Running:
+                res.status(200).send(statusLabels[currentStatus]);
+                break;
+
+            default:
+                res.status(503).send(statusLabels[currentStatus]);
+                break;
+        }
+    });
+
+    router.get('/health', (req, res) => {
+        switch (currentStatus) {
+            case HealthStatus.Running:
+                res.status(200).send(statusLabels[HealthStatus.Running]);
+                break;
+
+            default:
+                res.status(503).send(statusLabels[currentStatus]);
+                break;
+        }
+    });
+
+    return router;
+};
+
+export const updateStatus = (nextStatus: HealthStatus) => {
+    currentStatus = nextStatus;
+};