Add ApplicationContextTracer to Graphql Schema

- This helps set up the logging and metrics tracer

app/graphql/gitlab_schema.rb

@@ -11,6 +11,7 @@ class GitlabSchema < GraphQL::Schema
   AUTHENTICATED_MAX_DEPTH = 20
 
   # Tracers (order is important)
+  use Gitlab::Graphql::Tracers::ApplicationContextTracer
   use Gitlab::Graphql::Tracers::LoggerTracer
   use Gitlab::Graphql::GenericTracing # Old tracer which will be removed eventually
   use Gitlab::Graphql::Tracers::TimerTracer

lib/gitlab/graphql/tracers/application_context_tracer.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module Tracers
+      # This graphql-ruby tracer sets up `ApplicationContext` for certain operations.
+      class ApplicationContextTracer
+        def self.use(schema)
+          schema.tracer(self.new)
+        end
+
+        # See docs on expected interface for trace
+        # https://graphql-ruby.org/api-doc/1.12.17/GraphQL/Tracing
+        def trace(key, data)
+          case key
+          when "execute_query"
+            operation = known_operation(data)
+
+            ::Gitlab::ApplicationContext.with_context(caller_id: operation.to_caller_id) do
+              yield
+            end
+          else
+            yield
+          end
+        end
+
+        private
+
+        def known_operation(data)
+          # The library guarantees that we should have :query for execute_query, but we're being defensive here
+          query = data.fetch(:query, nil)
+
+          return ::Gitlab::Graphql::KnownOperations.UNKNOWN unless query
+
+          ::Gitlab::Graphql::KnownOperations.default.from_query(query)
+        end
+      end
+    end
+  end
+end

spec/lib/gitlab/graphql/tracers/application_context_tracer_spec.rb

+# frozen_string_literal: true
+require "fast_spec_helper"
+require "support/graphql/fake_tracer"
+require "support/graphql/fake_query_type"
+
+RSpec.describe Gitlab::Graphql::Tracers::ApplicationContextTracer do
+  let(:tracer_spy) { spy('tracer_spy') }
+  let(:default_known_operations) { ::Gitlab::Graphql::KnownOperations.new(['fooOperation']) }
+  let(:dummy_schema) do
+    schema = Class.new(GraphQL::Schema) do
+      use Gitlab::Graphql::Tracers::ApplicationContextTracer
+
+      query Graphql::FakeQueryType
+    end
+
+    fake_tracer = Graphql::FakeTracer.new(lambda do |key, *args|
+      tracer_spy.trace(key, Gitlab::ApplicationContext.current)
+    end)
+
+    schema.tracer(fake_tracer)
+
+    schema
+  end
+
+  before do
+    allow(::Gitlab::Graphql::KnownOperations).to receive(:default).and_return(default_known_operations)
+  end
+
+  it "sets application context during execute_query and cleans up afterwards", :aggregate_failures do
+    dummy_schema.execute("query fooOperation { helloWorld }")
+
+    # "parse" is just an arbitrary trace event that isn't setting caller_id
+    expect(tracer_spy).to have_received(:trace).with("parse", hash_excluding("meta.caller_id"))
+    expect(tracer_spy).to have_received(:trace).with("execute_query", hash_including("meta.caller_id" => "graphql:fooOperation")).once
+    expect(Gitlab::ApplicationContext.current).not_to include("meta.caller_id")
+  end
+
+  it "sets caller_id when operation is not known" do
+    dummy_schema.execute("query fuzz { helloWorld }")
+
+    expect(tracer_spy).to have_received(:trace).with("execute_query", hash_including("meta.caller_id" => "graphql:unknown")).once
+  end
+end

spec/requests/api/graphql_spec.rb

@@ -15,7 +15,7 @@ RSpec.describe 'GraphQL' do
       let(:expected_execute_query_log) do
         {
           "correlation_id" => kind_of(String),
-          "meta.caller_id" => "GraphqlController#execute",
+          "meta.caller_id" => "graphql:anonymous",
           "meta.client_id" => kind_of(String),
           "meta.feature_category" => "not_owned",
           "meta.remote_ip" => kind_of(String),