Remove per-web-transaction redis metrics

We still have those in logs if we need to see them per transaction.

changelogs/unreleased/bvl-remove-redis-metrics-per-web-transaction.yml

+---
+title: Remove per-web-transaction redis metrics
+merge_request: 38101
+author:
+type: other

config/initializers/zz_metrics.rb

@@ -147,7 +147,6 @@ if Gitlab::Metrics.enabled? && !Rails.env.test? && !(Rails.env.development? && d
   Gitlab::Application.configure do |config|
     config.middleware.use(Gitlab::Metrics::RackMiddleware)
     config.middleware.use(Gitlab::Middleware::RailsQueueDuration)
-    config.middleware.use(Gitlab::Metrics::RedisRackMiddleware)
     config.middleware.use(Gitlab::Metrics::ElasticsearchRackMiddleware)
   end
 

doc/administration/monitoring/prometheus/gitlab_metrics.md

@@ -97,8 +97,6 @@ The following metrics are available:
 | `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`                              |
-| `http_redis_requests_duration_seconds`                         | Histogram |                   13.1 | Redis requests duration during web transactions                                                     | `controller`, `action`                              |
-| `http_redis_requests_total`                                    | Counter   |                   13.1 | Redis requests count during web transactions                                                        | `controller`, `action`                              |
 | `http_elasticsearch_requests_duration_seconds` **(STARTER)**   | Histogram |                   13.1 | Elasticsearch requests duration during web transactions                                             | `controller`, `action`                              |
 | `http_elasticsearch_requests_total` **(STARTER)**              | Counter   |                   13.1 | Elasticsearch requests count during web transactions                                                | `controller`, `action`                              |
 | `pipelines_created_total`                                      | Counter   |                    9.4 | Counter of pipelines created                                                                        |                                                     |

lib/gitlab/metrics/redis_rack_middleware.rb

-# frozen_string_literal: true
-
-module Gitlab
-  module Metrics
-    # Rack middleware for tracking Redis metrics from Grape and Web requests.
-    class RedisRackMiddleware
-      def initialize(app)
-        @app = app
-      end
-
-      def call(env)
-        transaction = Gitlab::Metrics.current_transaction
-
-        @app.call(env)
-      ensure
-        record_metrics(transaction)
-      end
-
-      private
-
-      def record_metrics(transaction)
-        query_time = Gitlab::Instrumentation::Redis.query_time
-        request_count = Gitlab::Instrumentation::Redis.get_request_count
-
-        transaction.increment(:http_redis_requests_total, request_count) do
-          docstring 'Amount of calls to Redis servers during web requests'
-        end
-
-        transaction.observe(:http_redis_requests_duration_seconds, query_time) do
-          docstring 'Query time for Redis servers during web requests'
-          buckets Gitlab::Instrumentation::Redis::QUERY_TIME_BUCKETS
-        end
-      end
-    end
-  end
-end

spec/lib/gitlab/metrics/redis_rack_middleware_spec.rb

-# frozen_string_literal: true
-
-require 'spec_helper'
-
-RSpec.describe Gitlab::Metrics::RedisRackMiddleware do
-  let(:app) { double(:app) }
-  let(:middleware) { described_class.new(app) }
-  let(:env) { {} }
-  let(:transaction) { Gitlab::Metrics::WebTransaction.new(env) }
-
-  before do
-    allow(app).to receive(:call).with(env).and_return('wub wub')
-  end
-
-  describe '#call' do
-    let(:redis_query_time) { 0.1 }
-    let(:redis_requests_count) { 2 }
-
-    before do
-      allow(Gitlab::Instrumentation::Redis).to receive(:query_time) { redis_query_time }
-      allow(Gitlab::Instrumentation::Redis).to receive(:get_request_count) { redis_requests_count }
-      allow(Gitlab::Metrics).to receive(:current_transaction).and_return(transaction)
-    end
-
-    it 'calls the app' do
-      expect(middleware.call(env)).to eq('wub wub')
-    end
-
-    it 'records redis metrics' do
-      expect(transaction).to receive(:increment).with(:http_redis_requests_total, redis_requests_count)
-      expect(transaction).to receive(:observe).with(:http_redis_requests_duration_seconds, redis_query_time)
-
-      middleware.call(env)
-    end
-
-    it 'records redis metrics if an error is raised' do
-      expect(transaction).to receive(:increment).with(:http_redis_requests_total, redis_requests_count)
-      expect(transaction).to receive(:observe).with(:http_redis_requests_duration_seconds, redis_query_time)
-
-      allow(app).to receive(:call).with(env).and_raise(StandardError)
-
-      expect { middleware.call(env) }.to raise_error(StandardError)
-    end
-  end
-end