Debug Redis calls

ruby/lib/ci/queue/configuration.rb

@@ -19,6 +19,7 @@ def from_env(env)
             flaky_tests: load_flaky_tests(env['CI_QUEUE_FLAKY_TESTS']),
             statsd_endpoint: env['CI_QUEUE_STATSD_ADDR'],
             redis_ttl: env['CI_QUEUE_REDIS_TTL']&.to_i ||  8 * 60 * 60,
+            debug_log: env['CI_QUEUE_DEBUG_LOG'],
           )
         end
 
@@ -36,7 +37,7 @@ def initialize(
         grind_count: nil, max_duration: nil, failure_file: nil, max_test_duration: nil,
         max_test_duration_percentile: 0.5, track_test_duration: false, max_test_failed: nil,
         queue_init_timeout: nil, redis_ttl: 8 * 60 * 60, report_timeout: nil, inactive_workers_timeout: nil,
-        export_flaky_tests_file: nil, warnings_file: nil
+        export_flaky_tests_file: nil, warnings_file: nil, debug_log: nil,
       )
         @build_id = build_id
         @circuit_breakers = [CircuitBreaker::Disabled]
@@ -62,6 +63,7 @@ def initialize(
         @inactive_workers_timeout = inactive_workers_timeout
         @export_flaky_tests_file = export_flaky_tests_file
         @warnings_file = warnings_file
+        @debug_log = debug_log
       end
 
       def queue_init_timeout

ruby/lib/ci/queue/redis/base.rb

@@ -11,6 +11,25 @@ class Base
           ::SocketError, # https://github.com/redis/redis-rb/pull/631
         ].freeze
 
+        class RedisInstrumentation
+          def initialize(debug_log)
+            require 'logger'
+            @Logger.new(debug_log)
+          end
+
+          def call(command, redis_config)
+            result = super
+            @logger.info("#{command}: #{result}")
+            result
+          end
+
+          def call_pipelined(commands, redis_config)
+            result = super
+            @logger.info("#{commands}: #{result}")
+            result
+          end
+        end
+
         def initialize(redis_url, config)
           @redis_url = redis_url
           if ::Redis::VERSION > "5.0.0"
@@ -19,13 +38,20 @@ def initialize(redis_url, config)
               # Booting a CI worker is costly, so in case of a Redis blip,
               # it makes sense to retry for a while before giving up.
               reconnect_attempts: [0, 0, 0.1, 0.5, 1, 3, 5],
+              middlewares: middlewares,
             )
           else
             @redis = ::Redis.new(url: redis_url)
           end
           @config = config
         end
 
+        def middlewares
+          [].tap do |result|
+            result << RedisInstrumentation.new(config.debug_log) if config.debug_log
+          end
+        end
+
         def exhausted?
           queue_initialized? && size == 0
         end

ruby/lib/minitest/queue/runner.rb

@@ -586,6 +586,10 @@ def parser
             self.verbose = true
           end
 
+          opts.on("--debug-log", "Path to debug log file for e.g. Redis instrumentation") do |path|
+            self.debug_log = path
+          end
+
           opts.separator ""
           opts.separator "    retry: Replays a previous run in the same order."