@cloudnative/health-connect NPM

Cloud Health Connect

Cloud Health Connect provides a Connect Middleware for use in Express.js, Loopback and other frameworks that uses Cloud Health to provide:

Readiness checks
Liveness checks
Combined Health (Readiness and Liveness) checks
Shutdown handling

to enable applications for use with Kubernetes and Cloud Foundry based clouds.

Using Cloud Health Connect

Cloud Health Connect takes the status reported by Cloud Health and makes it available on the liveness and/or readiness URL endpoints that the middleware is configured to use.

The middleware writes the data returned by the Cloud Health module as JSON, and sets the HTTP Status Code as follows:

Cloud Health Status	Readiness Status Code	Liveness Status Code	Combined Health Status Code
STARTING	503 UNAVAILABLE	200 OK	503 UNAVAILABLE
UP	200 OK	200 OK	200 OK
DOWN	503 UNAVAILABLE	503 UNAVAILABLE	503 UNAVAILABLE
STOPPING	503 UNAVAILABLE	503 UNAVAILABLE	503 UNAVAILABLE
STOPPED	503 UNAVAILABLE	503 UNAVAILABLE	503 UNAVAILABLE
-	500 SERVER ERROR	500 SERVER ERROR	500 SERVER ERROR

Using Cloud Health with Node.js

Installation:
```
npm install @cloudnative/health-connect
```

Set up a HealthChecker:

const health = require('@cloudnative/health-connect');
let healthcheck = new health.HealthChecker();

Register a separate Liveness endpoint:
```
app.use('/live', health.LivenessEndpoint(healthcheck))
```
If no livessness checks are registered, this will report 200 OK and UP.
Register a separate readiness endpoint:
```
app.use('/ready', health.ReadinessEndpoint(healthcheck))
```
If no readiness checks are registered, this will report 200 OK and UP.
Register a combined health endpoint:
```
app.use('/health', health.HealthEndpoint(healthcheck))
```
If no readiness or liveness checks are registered, this will report 200 OK and UP.

For information on how to register startup, readiness, liveness and shutdown checks, see the Cloud Health documentation.

Health, Liveness and Readiness endpoints

The difference between liveness and readiness endpoints is the purpose: readiness should be used to denote whether an application is "ready" to receive requests, and liveness should be used to denote whether an application is "live" (vs. in a state where it should be restarted.

The combined health endpoint is designed for cloud technologies, such as Cloud Foundry which only support a single endpoint for both liveness and readiness checking.