[WIP]

mastodon_metrics_handler.rb

class MastodonMetricsHandler
  def call(env)
    host = env['HTTP_HOST']
    instance = fetch_instance_meta(host)
    stats = instance['stats']

    headers = {
      'Content-Type' => 'text/plain; charset=UTF-8',
    }
    body = [
      '# HELP mastodon_domain_count todo',
      '# TYPE mastodon_domain_count counter',
      "mastodon_domain_count #{stats['domain_count']}",
      '# HELP mastodon_status_count todo',
      '# TYPE mastodon_status_count counter',
      "mastodon_status_count #{stats['status_count']}",
      '# HELP mastodon_user_count todo',
      '# TYPE mastodon_user_count counter',
      "mastodon_user_count #{stats['user_count']}",
      '# HELP mastodon_version_info todo',
      '# TYPE mastodon_version_info gauge',
      "mastodon_version_info{version=\"#{instance['version']}\"} 1",
    ].join("\n")

    [200, headers, [body]]
  end

  private

  def fetch_instance_meta(host)
    req = http_request("https://#{host}/api/v1/instance")
    status, headers, body = req.join
    begin
      JSON.parse(body.join)
    rescue
      {}
    end
  end
end

MastodonMetricsHandler.new

statsd_mapping.yml

mappings:
  - match: Mastodon\.([^.]*)\.web\.(.*Controller)\.([^.]*)\.([^.]*)\.status\.(\d{3})
    match_type: regex
    name: mastodon_web_request
    labels:
      environment: $1
      controller: $2
      action: $3
      format: $4
      status: $5
  - match: Mastodon\.([^.]*)\.web\.(.*Controller)\.([^.]*)\.([^.]*)\.([^.]*)
    match_type: regex
    name: mastodon_web_${5}
    labels:
      environment: $1
      controller: $2
      action: $3
      format: $4

  - match: "Mastodon.*.db.tables.*.queries.*.duration"
    name: mastodon_db_${3}_duration
    labels:
      environment: $1
      table_name: $2

  - match: "Mastodon.*.cache.*.duration"
    name: mastodon_cache_${2}_duration
    labels:
      environment: $1

  - match: Mastodon\.([^.]*)\.sidekiq\.(.*(?:Worker|Scheduler))\.([^.]*)
    match_type: regex
    name: mastodon_sidekiq_${3}
    labels:
      environment: $1
      worker_name: $2
  - match: "Mastodon.*.sidekiq.queues.*.*"
    name: mastodon_sidekiq_queues_${3}
    labels:
      environment: $1
      queue_name: $2
  - match: "Mastodon.*.sidekiq.*"
    name: mastodon_sidekiq_${2}
    labels:
      environment: $1