Health-check middleware for Moleculer

The following originally comes from a gist available here: https://gist.github.com/icebob/c717ae22002b9ecaa4b253a67952da3a

Most credits go to @icebob. This repository only provides us a way to publish, maintain and perhaps customize this middleware.

Use it for Kubernetes liveness & readiness checks. The middleware opens a HTTP server on port 3001. To check, open the http://localhost:3001/live & http://localhost:3001/ready URLs.

Response

{
  "state": "up",
  "uptime": 7.419,
  "timestamp": 1562790370161
}

The state can be "starting" (503), "up" (200), "stopping" (503) or "down" (503).

Usage

Load with default options

// moleculer.config.js
const HealthMiddleware = require("./health-check.middleware.js");

module.exports = {
  middlewares: [
    HealthMiddleware()
  ]
};

Load with custom options

// moleculer.config.js
const HealthMiddleware = require("./health-check.middleware.js");

module.exports = {
  middlewares: [
    HealthMiddleware({
      port: 3333,
      readiness: {
        path: "/ready"
      },
      liveness: {
        path: "/live"
      }
    })
  ]
};

In order to check liveness and/or readiness a little deeper, you can also give a checker function which takes a callback. If you give a parameter to the callback you will tell the middlware to fail the liveness and/or readiness check. Also if you do not respond in a certain amount of time, the liveness and/or readiness check will fail.

// moleculer.config.js
const HealthMiddleware = require("./health-check.middleware.js");

module.exports = {
  middlewares: [
    HealthMiddleware({
      liveness: {
        checkerTimeoutMs: 30000, // default value
        checker: function(next) {
          // Execute here your liveness check...
          if (ok) {
            next();
          } else {
            next('error');
          }
        },
      },
    }),
  ],
};

Usage in Kubernetes

apiVersion: apps/v1
kind: Deployment
metadata:
  name: greeter
spec:
  selector:
    matchLabels:
      app: greeter
  replicas: 1
  template:
    metadata:
      labels:
        app: greeter
    spec:
      containers:
      - name: greeter
        image: moleculer/demo:1.4.2
        livenessProbe:
          httpGet:
            path: /live
            port: 3001
        readinessProbe:
          httpGet:
            path: /ready
            port: 3001