Add gitaly_calls to API structured logs

changelogs/unreleased/an-ap_log_gitaly_calls.yml

@@ -0,0 +1,5 @@
+---
+title: Add gitaly_calls attribute to API logs
+merge_request: 21496
+author:
+type: other

lib/api/api.rb

@@ -16,7 +16,8 @@ module API
                     GrapeLogging::Loggers::FilterParameters.new,
                     GrapeLogging::Loggers::ClientEnv.new,
                     Gitlab::GrapeLogging::Loggers::UserLogger.new,
-                    Gitlab::GrapeLogging::Loggers::QueueDurationLogger.new
+                    Gitlab::GrapeLogging::Loggers::QueueDurationLogger.new,
+                    Gitlab::GrapeLogging::Loggers::PerfLogger.new
                   ]
 
     allow_access_with_scope :api

lib/gitlab/grape_logging/loggers/perf_logger.rb

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+# This module adds additional performance metrics to the grape logger
+module Gitlab
+  module GrapeLogging
+    module Loggers
+      class PerfLogger < ::GrapeLogging::Loggers::Base
+        def parameters(_, _)
+          { gitaly_calls: Gitlab::GitalyClient.get_request_count }
+        end
+      end
+    end
+  end
+end