healthcheck-prototype

Health Checker

A proof-of-concept library for ExpressJS-based applications to add a health checking endpoint and provide a payload with the application's health check status.

Getting Started

Install with:

yarn add health-check

Add the following to your ExpressJS application:

import { HealthChecker } from "./healthcheck/HealthChecker";

The following example uses the Mongoose health checker against the MongoDB database connection.

const healthChecker = new HealthChecker();

this.app.use("/health", healthChecker.router);

Health Checking Services

Import the service checker for the service you want to check such as MongoDB, Redis, PostgreSQL, etc.:

import { MongooseServiceChecker } from "./healthcheck/MongooseServiceChecker";

Add the checker before the health check is invoked:

const mongoDBCheck = new MongooseServiceChecker(mongoose.connection);
healthChecker.register("mongo", mongoDBCheck);

Health Checking Status

All applications must return the following basic payload at the registered health route:

{
  "state": "UP"
}

For more advanced cases, such as when other services are registered on the health checker, the following information can appear:

{
  "state": "UP",
  "uptime": 100,
  "services": {
    "mongodb":
      {
        "state": "UP",
        "host": "mongo",
        "username": "XXX",
        "password": "XXX"
      },
    "redis":
      {
        "state": "UP"
      }
  }
}

When there is an error, or a DOWN state, the payload will typically contain an error message:

{
  "state": "DOWN",
  "message": "Could not allocate port 27017"
}

The state can take the following values:

• UP: The application or service is up and operating normally
• DOWN: The applicaiton or service is down and not operating normally such as it could not connect to a database or get a port properly.
• CONNECTING: Currently trying to establish a connection before moving to the UP state
• DISCONNECTING: Currently moving from the UP state to DOWN state by disconnecting the network.

Uptime is in milliseconds.

LICENSE

IBM HealthCheck Copyright 2017 IBM

This product includes software developed at IBM.