1 files changed, 43 insertions, 12 deletions
diff --git a/lib/gitlab/metrics/requests_rack_middleware.rb b/lib/gitlab/metrics/requests_rack_middleware.rb
index f6bda0dbea4..23d7eb67312 100644
--- a/lib/gitlab/metrics/requests_rack_middleware.rb
+++ b/lib/gitlab/metrics/requests_rack_middleware.rb
@@ -3,43 +3,70 @@
 module Gitlab
   module Metrics
     class RequestsRackMiddleware
-      HTTP_METHODS = %w(delete get head options patch post put).to_set.freeze
+      HTTP_METHODS = {
+        "delete" => %w(200 202 204 303 400 401 403 404 500 503),
+        "get" => %w(200 204 301 302 303 304 307 400 401 403 404 410 422 429 500 503),
+        "head" => %w(200 204 301 302 303 401 403 404 410 500),
+        "options" => %w(200 404),
+        "patch" => %w(200 202 204 400 403 404 409 416 500),
+        "post" => %w(200 201 202 204 301 302 303 304 400 401 403 404 406 409 410 412 422 429 500 503),
+        "put" => %w(200 202 204 400 401 403 404 405 406 409 410 422 500)
+      }.freeze
 
       HEALTH_ENDPOINT = /^\/-\/(liveness|readiness|health|metrics)\/?$/.freeze
 
       FEATURE_CATEGORY_HEADER = 'X-Gitlab-Feature-Category'
       FEATURE_CATEGORY_DEFAULT = 'unknown'
 
+      # These were the top 5 categories at a point in time, chosen as a
+      # reasonable default. If we initialize every category we'll end up
+      # with an explosion in unused metric combinations, but we want the
+      # most common ones to be always present.
+      FEATURE_CATEGORIES_TO_INITIALIZE = ['authentication_and_authorization',
+                                          'code_review', 'continuous_integration',
+                                          'not_owned', 'source_code_management',
+                                          FEATURE_CATEGORY_DEFAULT].freeze
+
       def initialize(app)
         @app = app
       end
 
-      def self.http_request_total
-        @http_request_total ||= ::Gitlab::Metrics.counter(:http_requests_total, 'Request count')
+      def self.http_requests_total
+        ::Gitlab::Metrics.counter(:http_requests_total, 'Request count')
       end
 
       def self.rack_uncaught_errors_count
-        @rack_uncaught_errors_count ||= ::Gitlab::Metrics.counter(:rack_uncaught_errors_total, 'Request handling uncaught errors count')
+        ::Gitlab::Metrics.counter(:rack_uncaught_errors_total, 'Request handling uncaught errors count')
       end
 
       def self.http_request_duration_seconds
-        @http_request_duration_seconds ||= ::Gitlab::Metrics.histogram(:http_request_duration_seconds, 'Request handling execution time',
-                                                           {}, [0.05, 0.1, 0.25, 0.5, 0.7, 1, 2.5, 5, 10, 25])
+        ::Gitlab::Metrics.histogram(:http_request_duration_seconds, 'Request handling execution time',
+                                    {}, [0.05, 0.1, 0.25, 0.5, 0.7, 1, 2.5, 5, 10, 25])
       end
 
       def self.http_health_requests_total
-        @http_health_requests_total ||= ::Gitlab::Metrics.counter(:http_health_requests_total, 'Health endpoint request count')
+        ::Gitlab::Metrics.counter(:http_health_requests_total, 'Health endpoint request count')
       end
 
-      def self.initialize_http_request_duration_seconds
-        HTTP_METHODS.each do |method|
+      def self.initialize_metrics
+        # This initialization is done to avoid gaps in scraped metrics after
+        # restarts. It makes sure all counters/histograms are available at
+        # process start.
+        #
+        # For example `rate(http_requests_total{status="500"}[1m])` would return
+        # no data until the first 500 error would occur.
+        HTTP_METHODS.each do |method, statuses|
           http_request_duration_seconds.get({ method: method })
+
+          statuses.product(FEATURE_CATEGORIES_TO_INITIALIZE) do |status, feature_category|
+            http_requests_total.get({ method: method, status: status, feature_category: feature_category })
+          end
         end
       end
 
       def call(env)
         method = env['REQUEST_METHOD'].downcase
-        method = 'INVALID' unless HTTP_METHODS.include?(method)
+        method = 'INVALID' unless HTTP_METHODS.key?(method)
         started = Time.now.to_f
         health_endpoint = health_endpoint?(env['PATH_INFO'])
         status = 'undefined'
@@ -61,9 +88,13 @@ module Gitlab
           raise
         ensure
           if health_endpoint
-            RequestsRackMiddleware.http_health_requests_total.increment(status: status, method: method)
+            RequestsRackMiddleware.http_health_requests_total.increment(status: status.to_s, method: method)
           else
-            RequestsRackMiddleware.http_request_total.increment(status: status, method: method, feature_category: feature_category || FEATURE_CATEGORY_DEFAULT)
+            RequestsRackMiddleware.http_requests_total.increment(
+              status: status.to_s,
+              method: method,
+              feature_category: feature_category.presence || FEATURE_CATEGORY_DEFAULT
+            )
           end
         end
       end