Debugging Datadog agent in Ruby on Rails app

routes.rb

Rails.application.routes.draw do
  get '/health', to: proc { [200, {}, ['ok']] }, as: :app_health_check

  get '/dd', to: proc {
    port_is_open = Socket.tcp('localhost', 8126, connect_timeout: 5) { true } rescue false
    res = "Datadog port is open: #{port_is_open}"
    [200, {}, [res]]
  }, as: :dd_health_check
end

Solution

Wait for Datadog agent has started and listening on a port 8126:

wait_for_datadog.sh:

#!/bin/env sh

max_attempts=20
attempts=0

while ! nc -z localhost 8126; do
  if [ $attempts -ge $max_attempts ]; then
    echo "Max attempts reached. Datadog agent did not start."
    exit 1
  fi

  echo "Waiting for Datadog agent to start... Attempt: $((attempts+1))"
  attempts=$((attempts+1))
  sleep 1
done

Procfile:

web: ./wait_for_datadog.sh && bundle exec puma -p ${PORT:-3000} -e production