feat: redis metrics [wip]

Author: zvkemp

instrumentation/redis/Appraisals

@@ -1,5 +1,23 @@
 # frozen_string_literal: true
 
+appraise 'redis-4.x-metrics-sdk' do
+  gem 'redis-client', '~> 0.22'
+  gem 'redis', '~> 4.8'
+  gem 'opentelemetry-metrics-sdk', github: "zvkemp/opentelemetry-ruby", glob: 'metrics_sdk/*.gemspec', ref: "metrics-kwargs"
+  gem 'opentelemetry-metrics-api', github: "zvkemp/opentelemetry-ruby", glob: 'metrics_api/*.gemspec', ref: "metrics-kwargs"
+end
+
+appraise 'redis-5.x-metrics-sdk' do
+  gem 'redis', '~> 5.0'
+  gem 'opentelemetry-metrics-sdk', github: "zvkemp/opentelemetry-ruby", glob: 'metrics_sdk/*.gemspec', ref: "metrics-kwargs"
+  gem 'opentelemetry-metrics-api', github: "zvkemp/opentelemetry-ruby", glob: 'metrics_api/*.gemspec', ref: "metrics-kwargs"
+end
+
+appraise 'redis-5.x-metrics-api' do
+  gem 'redis', '~> 5.0'
+  gem 'opentelemetry-metrics-api', github: "zvkemp/opentelemetry-ruby", glob: 'metrics_api/*.gemspec', ref: "metrics-kwargs"
+end
+
 appraise 'redis-4.x' do
   gem 'redis-client', '~> 0.22'
   gem 'redis', '~> 4.8'

instrumentation/redis/Gemfile

@@ -11,3 +11,5 @@ gemspec
 group :test do
   gem 'opentelemetry-instrumentation-base', path: '../base'
 end
+
+gem 'pry-byebug'

instrumentation/redis/lib/opentelemetry/instrumentation/redis/instrumentation.rb

@@ -22,16 +22,32 @@ class Instrumentation < OpenTelemetry::Instrumentation::Base
         option :peer_service,                 default: nil,   validate: :string
         option :trace_root_spans,             default: true,  validate: :boolean
         option :db_statement,                 default: :obfuscate, validate: %I[omit include obfuscate]
+        option :metrics,                      default: false, validate: :boolean
+
+        # https://opentelemetry.io/docs/specs/semconv/database/database-metrics/#metric-dbclientoperationduration
+        histogram 'db.client.operation.duration',
+                  attributes: { 'db.system.name' => 'redis' },
+                  unit: 's',
+                  boundaries: [0.001, 0.005, 0.01, 0.05, 0.1, 0.5, 1, 5, 10]
+
+        def client_operation_duration_histogram
+          histogram('db.client.operation.duration')
+        end
 
         private
 
         def require_dependencies
           require_relative 'patches/redis_v4_client' if defined?(::Redis) && ::Redis::VERSION < '5'
-          require_relative 'middlewares/redis_client' if defined?(::RedisClient)
+
+          return unless defined?(::RedisClient)
+
+          require_relative 'middlewares/redis_client'
+          require_relative 'middlewares/redis_client_metrics'
         end
 
         def patch_client
           ::RedisClient.register(Middlewares::RedisClientInstrumentation) if defined?(::RedisClient)
+          ::RedisClient.register(Middlewares::RedisClientMetrics) if defined?(::RedisClient)
           ::Redis::Client.prepend(Patches::RedisV4Client) if defined?(::Redis) && ::Redis::VERSION < '5'
         end
       end

instrumentation/redis/lib/opentelemetry/instrumentation/redis/middlewares/redis_client.rb

@@ -49,6 +49,7 @@ def span_attributes(redis_config)
 
             attributes['db.redis.database_index'] = redis_config.db unless redis_config.db.zero?
             attributes['peer.service'] = instrumentation.config[:peer_service] if instrumentation.config[:peer_service]
+
             attributes.merge!(OpenTelemetry::Instrumentation::Redis.attributes)
             attributes
           end

instrumentation/redis/lib/opentelemetry/instrumentation/redis/middlewares/redis_client_metrics.rb

@@ -0,0 +1,66 @@
+# frozen_string_literal: true
+
+# Copyright The OpenTelemetry Authors
+#
+# SPDX-License-Identifier: Apache-2.0
+
+module OpenTelemetry
+  module Instrumentation
+    module Redis
+      module Middlewares
+        # Adapter for redis-client instrumentation interface
+        module RedisClientMetrics
+          def call(command, redis_config)
+            return super unless (histogram = instrumentation.client_operation_duration_histogram)
+
+            timed(histogram, command.first, redis_config) do
+              super
+            end
+          end
+
+          def call_pipelined(commands, redis_config)
+            return super unless (histogram = instrumentation.client_operation_duration_histogram)
+
+            timed(histogram, 'PIPELINE', redis_config) do
+              super
+            end
+          end
+
+          private
+
+          def timed(histogram, operation_name, redis_config)
+            t0 = monotonic_now
+
+            yield.tap do
+              duration = monotonic_now - t0
+
+              histogram.record(duration, attributes: metric_attributes(redis_config, operation_name))
+            end
+          end
+
+          def monotonic_now
+            Process.clock_gettime(Process::CLOCK_MONOTONIC, :float_second)
+          end
+
+          def metric_attributes(redis_config, operation_name)
+            attributes = {
+              'db.system' => 'redis',
+              'db.operation.name' => operation_name,
+              'net.peer.name' => redis_config.host,
+              'net.peer.port' => redis_config.port
+            }
+
+            attributes['db.redis.database_index'] = redis_config.db unless redis_config.db.zero?
+            attributes['peer.service'] = instrumentation.config[:peer_service] if instrumentation.config[:peer_service]
+            attributes.merge!(OpenTelemetry::Instrumentation::Redis.attributes)
+            attributes
+          end
+
+          def instrumentation
+            Redis::Instrumentation.instance
+          end
+        end
+      end
+    end
+  end
+end