Alert if `calls_gitaly` declaration missing

- Move `calls_gitaly_check` to public
- Add instrumentation for flagging missing CallsGitaly declarations
- Wrap resolver proc in before-and-after Gitaly counts to get the net
Gitaly call count for the resolver.

1 files changed, 30 insertions, 0 deletions

diff --git a/lib/gitlab/graphql/calls_gitaly/instrumentation.rb b/lib/gitlab/graphql/calls_gitaly/instrumentation.rb
new file mode 100644
index 00000000000..ca54e12c049
--- /dev/null
+++ b/lib/gitlab/graphql/calls_gitaly/instrumentation.rb
@@ -0,0 +1,30 @@
+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module CallsGitaly
+      class Instrumentation
+        # Check if any `calls_gitaly: true` declarations need to be added
+        def instrument(_type, field)
+          type_object = field.metadata[:type_class]
+          return field unless type_object && type_object.respond_to?(:calls_gitaly_check)
+
+          old_resolver_proc = field.resolve_proc
+          wrapped_proc = gitaly_wrapped_resolve(old_resolver_proc, type_object)
+          field.redefine { resolve(wrapped_proc) }
+        end
+
+        def gitaly_wrapped_resolve(old_resolver_proc, type_object)
+          proc do |parent_typed_object, args, ctx|
+            previous_gitaly_call_count = Gitlab::GitalyClient.get_request_count
+
+            old_resolver_proc.call(parent_typed_object, args, ctx)
+
+            current_gitaly_call_count = Gitlab::GitalyClient.get_request_count
+            type_object.calls_gitaly_check(current_gitaly_call_count - previous_gitaly_call_count)
+          end
+        end
+      end
+    end
+  end
+end