Monitor GraphQL with Prometheus

Extends graphql's platform tracing class to observe duration
of graphql methods.

In graphql 1.8.11 is added prometheus class but it's not very useful
for us because it uses prometheus_exporter to export results.

1 files changed, 43 insertions, 0 deletions

diff --git a/lib/gitlab/graphql/tracing.rb b/lib/gitlab/graphql/tracing.rb
new file mode 100644
index 00000000000..6b505e4262b
--- /dev/null
+++ b/lib/gitlab/graphql/tracing.rb
@@ -0,0 +1,43 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    class Tracing < GraphQL::Tracing::PlatformTracing
+      self.platform_keys = {
+        'lex' => 'graphql.lex',
+        'parse' => 'graphql.parse',
+        'validate' => 'graphql.validate',
+        'analyze_query' => 'graphql.analyze',
+        'analyze_multiplex' => 'graphql.analyze',
+        'execute_multiplex' => 'graphql.execute',
+        'execute_query' => 'graphql.execute',
+        'execute_query_lazy' => 'graphql.execute',
+        'execute_field' => 'graphql.execute',
+        'execute_field_lazy' => 'graphql.execute'
+      }
+
+      def platform_field_key(type, field)
+        "#{type.name}.#{field.name}"
+      end
+
+      def platform_trace(platform_key, key, data, &block)
+        start = Gitlab::Metrics::System.monotonic_time
+
+        yield
+      ensure
+        duration = Gitlab::Metrics::System.monotonic_time - start
+
+        graphql_duration_seconds.observe({ platform_key: platform_key, key: key }, duration)
+      end
+
+      private
+
+      def graphql_duration_seconds
+        @graphql_duration_seconds ||= Gitlab::Metrics.histogram(
+          :graphql_duration_seconds,
+          'GraphQL execution time'
+        )
+      end
+    end
+  end
+end