1 files changed, 70 insertions, 0 deletions
diff --git a/lib/gitlab/tracing/redis.rb b/lib/gitlab/tracing/redis.rb
new file mode 100644
index 00000000000..92be44c2d19
--- /dev/null
+++ b/lib/gitlab/tracing/redis.rb
@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+require 'opentracing'
+
+module Gitlab
+  module Tracing
+    module Redis
+      include Common
+
+      MAX_SENT_REDIS_COMMAND_LENGTH = 240
+
+      def self.instrument_client
+        ::Redis::Client.class_exec do
+          prepend RedisTracingInstrumented
+        end
+      end
+
+      private
+
+      module RedisTracingInstrumented
+        include Common
+        def call(*args, &block)
+          # For Redis calls, certain systems (Sidekiq in particular) will poll Redis
+          # periodically, outside of a trace scope. In this event, don't trace the
+          # call
+          scope = OpenTracing.scope_manager.active
+          return super(*args, &block) unless scope
+
+          start_active_span(operation_name: "redis.call",
+            tags: {
+              :component =>       'redis',
+              :'span.kind' =>     'client',
+              :'db.host' =>       self.host,
+              :'db.port' =>       self.port,
+              :'redis.db' =>      self.db,
+              :'redis.command' => quantize_redis_arguments(*args),
+              :'redis.args.count' => args.length
+            }) do |span|
+            super(*args, &block)
+          end
+        end
+
+        # Turns an array of redis arguments into a trace-worthy string
+        def quantize_redis_arguments(args)
+          args.inject("") do |memo, arg|
+            str = ""
+            begin
+              str = arg.to_s.encode('UTF-8', 'binary', invalid: :replace, undef: :replace, replace: '')
+            rescue
+              # Don't stumble on encoding errors while generating tracing
+              str = "?"
+            end
+
+            str = str.slice(0, 19) + "…" if str.length > 20
+
+            memo = memo == "" ? str : memo + " " + str
+            if memo.length > MAX_SENT_REDIS_COMMAND_LENGTH
+              memo = memo.slice(0, MAX_SENT_REDIS_COMMAND_LENGTH - 1) + "…"
+              # No need to iterate over the rest of the arguments
+              break memo
+            end
+
+            memo
+          end
+        end
+      end
+    end
+  end
+end
+