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fastify-healthcheck

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Fastify Plugin to serve responses that report about the web application, if it's still running and alive (health checks).

This is very useful with Containers like Docker and orchestrators like Kubernetes.

With this plugin, Fastify by default expose an healthcheck route configured for /health GET requests, and even a script that can be executed to get content via HTTP GET from that running web application.

Usage

The plugin can be used without specifying options, so good default values will be used, but if needed can be specified:

  • healthcheckUrl, to set a different uri for the healthcheck route
  • healthcheckUrlDisable, to not publish the healthcheck route
  • healthcheckUrlAlwaysFail, to always return failure responses (useful to test failure responses)
  • exposeUptime, to return even Node.js process uptime (by default disabled)
  • underPressureOptions, for options to send directly to under-pressure
  • schemaOptions, for options to use for route schema (no default value provided)

Under the hood, the healthcheck status is determined by the @fastify/under-pressure plugin, used here as a dependency; so it's possible to specify all its configuration options in related option.

To use all default values for healthcheck options, do not set its options (or set with undefined values); in that way no under-pressure specific options will be overridden by them.

Sample usage:

const fastify = require('fastify')()

// example without specifying options, returning a default healthcheck
// route mapped to '/health' that only reply to a GET request
fastify.register(require('fastify-healthcheck'))
// or
// example with custom healthcheck url and response to always fail
// fastify.register(require('fastify-healthcheck'), { healthcheckUrl: '/custom-health', healthcheckUrlAlwaysFail: true })
//

fastify.listen({ port: 3000, host: 'localhost' })

// To test, for example (in another terminal session) do:
// `npm start`, or
// `curl http://127.0.0.1:3000/health` => returning an HTTP response 200 (OK)
// and a JSON response like: {"statusCode":200,"status":"ok"}
// or run the healthcheck script, for example with:
// `node src/healthcheck http://localhost:3000/health`
// and get the same HTTP response seen before

In the example folder there is a simple server scripts that uses the plugin (inline but it's the same using it from npm registry).

The file Dockerfile.example is a sample container definition for the example webapp (using the plugin) to show Docker HEALTHCHECK directive both using 'curl' (but commented) and calling the healthcheck script available by the plugin. For convenience, all Docker commands have been defined in package.json, to run many of them in a simple way (with npm run custom-command), like in the following sequence:

  • docker:build, to build the image, where the entry point is the example
  • docker:build:fail, to build the image, but as entry point the example that is triggering the Service Unavailable error (HTTP 503) in the healthcheck route
  • docker:run, to start the container from generated image, in detached mode
  • docker:healthcheck-manual, to run the healthcheck script in the container but manually
  • docker:status, to get the health status of the container
  • and others like: docker:inspect (interactive), docker:log (C to close), docker:process, etc ...
  • docker:stop, to stop running container
  • docker:clean, to remove generated image

Requirements

Fastify ^5.0.0 , Node.js 20 LTS (20.9.0) or later. Note that plugin releases 4.x are for Fastify 4.x, 5.x for Fastify 5.x, etc.

Sources

Source code is all inside main repo: fastify-healthcheck.

Documentation generated from source code (library API): here.

Note

To fully encapsulate under-pressure features inside the scope of this plugin, the plugin is not exposed by fastify-plugin; for more info look here, here.

The plugin map a default endpoint on the URI /health to be called via GET, but it's possible to change it with the setting 'url' in plugin options.

The plugin exposes even another script that tries to get some content (via HTTP GET) from the current web application where it's running. In a container environment this could be useful to let containers runtime do the healthcheck without the need to use other tools like curl or wget that must be available in the container.

Both approaches could be useful in most common cases, like Kubernetes HTTP GET, or Kubernetes EXEC or Docker HEALTHCHECK, or others similar.

Note that the healthcheck script gets the URL to call from the command-line, but if not specified it will use a default value of http://localhost:3000/health.

To execute the healthcheck script from another Node.js project/package, you need to run something like: node node_modules/fastify-healthcheck/src/healthcheck http://localhost:8000/health, with the webapp exposed to the port 8000 in this case.

License

Licensed under Apache-2.0.