Improve StatsD instrumentation

config/initializers/statsd.rb

@@ -3,18 +3,11 @@
 StatsD.prefix              = 'mastodon'
 StatsD.default_sample_rate = 1
 
-StatsDMonitor.extend(StatsD::Instrument)
-StatsDMonitor.statsd_measure(:call, 'request.duration')
+ActiveSupport::Notifications.subscribe(/performance/) do |name, _start, _finish, _id, payload|
+  action      = payload[:action] || :increment
+  measurement = payload[:measurement]
+  value       = payload[:value]
+  key_name    = "#{name}.#{measurement}"
 
-STATSD_REQUEST_METRICS = {
-  'request.status.success'               => 200,
-  'request.status.not_found'             => 404,
-  'request.status.too_many_requests'     => 429,
-  'request.status.internal_server_error' => 500,
-}.freeze
-
-STATSD_REQUEST_METRICS.each do |name, code|
-  StatsDMonitor.statsd_count_if(:call, name) do |status, _env, _body|
-    status.to_i == code
-  end
+  StatsD.send(action.to_s, key_name, (value || 1))
 end