Remove status from http_request_duration_seconds

This removes the status label from the http_request_duration_seconds
histogram. For error rates, we've moved the status label to the
http_requests_total counter.

doc/administration/monitoring/prometheus/gitlab_metrics.md

@@ -91,8 +91,8 @@ The following metrics are available:
 | `gitlab_transaction_rails_queue_duration_total`                | Counter   |                    9.4 | Measures latency between GitLab Workhorse forwarding a request to Rails                             | `controller`, `action`                              |
 | `gitlab_transaction_view_duration_total`                       | Counter   |                    9.4 | Duration for views                                                                                  | `controller`, `action`, `view`                      |
 | `gitlab_view_rendering_duration_seconds`                       | Histogram |                   10.2 | Duration for views (histogram)                                                                      | `controller`, `action`, `view`                      |
-| `http_requests_total`                                          | Counter   |                    9.4 | Rack request count                                                                                  | `method`                                            |
-| `http_request_duration_seconds`                                | Histogram |                    9.4 | HTTP response time from rack middleware                                                             | `method`, `status`                                  |
+| `http_requests_total`                                          | Counter   |                    9.4 | Rack request count                                                                                  | `method`, `status`                                  |
+| `http_request_duration_seconds`                                | Histogram |                    9.4 | HTTP response time from rack middleware                                                             | `method`                                            |
 | `gitlab_transaction_db_count_total`                            | Counter   |                   13.1 | Counter for total number of SQL calls                                                               | `controller`, `action`                              |
 | `gitlab_transaction_db_write_count_total`                      | Counter   |                   13.1 | Counter for total number of write SQL calls                                                         | `controller`, `action`                              |
 | `gitlab_transaction_db_cached_count_total`                     | Counter   |                   13.1 | Counter for total number of cached SQL calls                                                        | `controller`, `action`                              |

lib/gitlab/metrics/requests_rack_middleware.rb

@@ -3,15 +3,7 @@
 module Gitlab
   module Metrics
     class RequestsRackMiddleware
-      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
+      HTTP_METHODS = %w(delete get head options patch post put).to_set.freeze
 
       HEALTH_ENDPOINT = /^\/-\/(liveness|readiness|health|metrics)\/?$/.freeze
 
@@ -40,16 +32,14 @@ module Gitlab
       end
 
       def self.initialize_http_request_duration_seconds
-        HTTP_METHODS.each do |method, statuses|
-          statuses.each do |status|
-            http_request_duration_seconds.get({ method: method, status: status.to_s })
-          end
+        HTTP_METHODS.each do |method|
+          http_request_duration_seconds.get({ method: method })
         end
       end
 
       def call(env)
         method = env['REQUEST_METHOD'].downcase
-        method = 'INVALID' unless HTTP_METHODS.key?(method)
+        method = 'INVALID' unless HTTP_METHODS.include?(method)
         started = Time.now.to_f
         health_endpoint = health_endpoint?(env['PATH_INFO'])
         status = 'undefined'
@@ -62,7 +52,7 @@ module Gitlab
           feature_category = headers&.fetch(FEATURE_CATEGORY_HEADER, nil)
 
           unless health_endpoint
-            RequestsRackMiddleware.http_request_duration_seconds.observe({ method: method, status: status.to_s }, elapsed)
+            RequestsRackMiddleware.http_request_duration_seconds.observe({ method: method }, elapsed)
           end
 
           [status, headers, body]

spec/lib/gitlab/metrics/requests_rack_middleware_spec.rb

@@ -32,7 +32,7 @@ RSpec.describe Gitlab::Metrics::RequestsRackMiddleware do
       end
 
       it 'measures execution time' do
-        expect(described_class).to receive_message_chain(:http_request_duration_seconds, :observe).with({ status: '200', method: 'get' }, a_positive_execution_time)
+        expect(described_class).to receive_message_chain(:http_request_duration_seconds, :observe).with({ method: 'get' }, a_positive_execution_time)
 
         Timecop.scale(3600) { subject.call(env) }
       end
@@ -77,7 +77,7 @@ RSpec.describe Gitlab::Metrics::RequestsRackMiddleware do
             it 'records the request duration' do
               expect(described_class)
                 .to receive_message_chain(:http_request_duration_seconds, :observe)
-                      .with({ method: 'get', status: '200' }, a_positive_execution_time)
+                      .with({ method: 'get' }, a_positive_execution_time)
 
               subject.call(env)
             end
@@ -137,10 +137,8 @@ RSpec.describe Gitlab::Metrics::RequestsRackMiddleware do
     describe '.initialize_http_request_duration_seconds' do
       it "sets labels" do
         expected_labels = []
-        described_class::HTTP_METHODS.each do |method, statuses|
-          statuses.each do |status|
-            expected_labels << { method: method, status: status.to_s }
-          end
+        described_class::HTTP_METHODS.each do |method|
+          expected_labels << { method: method }
         end
 
         described_class.initialize_http_request_duration_seconds