Class: Usps::Support::HealthController

Inherits:
ActionController::Base
  • Object
show all
Defined in:
app/controllers/usps/support/health_controller.rb

Overview

Base controller for external synthetic health probes (see the infrastructure repo’s doc/application_health_probes.md). Unlike Rails’ /up (boot-only) and nginx’s static /instance-health-check, this exercises an app’s *critical dependencies* and returns the sentinel “HEALTHCHECK_OK <app>” only when every check passes — a Route 53 HTTPS_STR_MATCH probe asserts the “HEALTHCHECK_OK” prefix, so a quiet app-level failure flips the Statuspage component even with no organic traffic.

Host apps subclass this and override #checks to pick which dependencies to probe, e.g.

class HealthController < Usps::Support::HealthController
  private
  def checks = { database: check_database, redis: check_redis }
end

and route to it (‘get ’health’ => ‘health#show’‘). The check_* primitives below each return a boolean and never raise, so the action always responds. Apps run only the checks for the dependencies they actually configure — admin-console has no HQ connection, so it omits check_hq_database; an iMIS-backed app adds check_imis; a custom downstream is check_http(url).

Inherits ActionController::Base directly — NOT the host’s ApplicationController — to bypass Devise auth, Pundit authorization, PaperTrail, and especially ‘allow_browser`, whose modern-browser gate would 406 Route 53’s non-browser prober and fail the probe for the wrong reason.

Constant Summary collapse

SENTINEL_PREFIX =

rubocop:disable Rails/ApplicationController

'HEALTHCHECK_OK'

Instance Method Summary collapse

Instance Method Details

#show ⇒ Object 



32
33
34
35
36
37
38
39
40
41
42
 
# File 'app/controllers/usps/support/health_controller.rb', line 32

def show
  results = checks
  healthy = results.values.all?

  body = "#{healthy ? "#{SENTINEL_PREFIX} #{app_name}" : "HEALTHCHECK_FAIL #{app_name}"}\n"
  results.each { |name, ok| body << "#{name}=#{ok ? 'ok' : 'fail'}\n" }

  response.set_header('Cache-Control', 'no-store')
  response.set_header('Retry-After', '30') unless healthy
  render(plain: body, content_type: 'text/plain', status: healthy ? :ok : :service_unavailable)
end