helthcheck

name	helthcheck
description	Use when the app needs a health check endpoint for a load balancer or uptime monitor. Covers installing plug_checkup at /health, configuring checks, and adding custom checkups.
user-invocable	true

Health Check Endpoint

Adds a /health endpoint via plug_checkup. It returns HTTP 200 when the app and its dependencies (DB, Redis, downstream services) are healthy, and a non-200 when they are not — so a load balancer or uptime monitor can route around an unhealthy instance.

When to use

• The app is deployed behind a load balancer or platform (Fly, Render, AWS, Kubernetes) that needs a health probe URL.
• You want an uptime monitor (BetterStack, Pingdom, UptimeRobot) to confirm the app and its dependencies are reachable.
• Don't reach for this if you only need a bare liveness ping with no dependency checks — a one-line Plug returning 200 is simpler.

Dependencies

• Requires: None.
• Recommended: None.

Install

mix saaskit.feature.install helthcheck

Adds the plug_checkup package and wires the /health route. No install decisions to answer.

What it generates

• Adds plug_checkup to mix.exs deps.
• A health check plug/route mounted at /health in lib/my_app_web/router.ex.
• A checkup definition module that lists the checks run on each request (DB connectivity by default).

Configuration

plug_checkup is configured through the checks list passed to the plug rather than config/*.exs. The default check verifies the repo is reachable.

Tweaking for your app

Add a custom checkup for a downstream dependency. Define a check module:

# lib/my_app/health/redis_check.ex
defmodule MyApp.Health.RedisCheck do
  def call do
    case MyApp.Redis.ping() do
      :ok -> :ok
      error -> {:error, error}
    end
  end
end

Register it alongside the default DB check where the health plug is mounted:

# lib/my_app_web/router.ex
forward "/health", PlugCheckup,
  PlugCheckup.Options.new(
    json_encoder: Jason,
    checks: [
      %PlugCheckup.Check{name: "DB", module: MyApp.Health.DBCheck, function: :call},
      %PlugCheckup.Check{name: "Redis", module: MyApp.Health.RedisCheck, function: :call}
    ]
  )

• Move the path: change "/health" in the forward/2 call to e.g. "/healthz" for Kubernetes conventions.
• Cache results: set time_to_cache in PlugCheckup.Options.new/1 to avoid hammering dependencies on every probe.
• Tighten checks: any function returning :ok or {:error, reason} is a valid check — add one per external service you depend on.

After install

• mix deps.get — fetch plug_checkup.
• Hit /health in the browser and confirm it returns HTTP 200.
• Point your load balancer / uptime monitor (Fly, Render, AWS, BetterStack) at /health.
• Add custom checkup modules for any downstream services you depend on.