Add body metadata to instrumentation

CHANGELOG.md

@@ -19,6 +19,7 @@
 * [#2603](https://github.com/ruby-grape/grape/pull/2603): Remove `namespace_stackable_with_hash` from public interface and move to internal InheritableSetting - [@ericproulx](https://github.com/ericproulx).
 * [#2604](https://github.com/ruby-grape/grape/pull/2604): Enable branch coverage  - [@ericproulx](https://github.com/ericproulx).
 * [#2605](https://github.com/ruby-grape/grape/pull/2605): Add Rack 3.2 support with new gemfile and CI integration - [@ericproulx](https://github.com/ericproulx).
+* [#2608](https://github.com/ruby-grape/grape/pull/2608): Add body metadata to `ActiveSupport::Notifications` instrumentation - [@braktar](https://github.com/braktar).
 * Your contribution here.
 
 #### Fixes

lib/grape/dsl/body_metadata.rb

@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+module Grape
+  module DSL
+    # Module for extracting body metadata for endpoint notifications
+    # This provides information about the response body without reading its content
+    module BodyMetadata
+      # Extract body metadata for endpoint notifications
+      # This provides information about the response body without reading its content
+      def extract_endpoint_body_metadata
+        metadata = {
+          has_body: instance_variable_defined?(:@body) && [email protected]?,
+          has_stream: instance_variable_defined?(:@stream) && [email protected]?,
+          status: instance_variable_defined?(:@status) ? @status : nil
+        }
+
+        if metadata[:has_body]
+          metadata[:body_type] = @body.class.name
+          metadata[:body_responds_to_size] = @body.respond_to?(:size)
+          metadata[:body_size] = @body.respond_to?(:size) ? @body.size : nil
+        end
+
+        if metadata[:has_stream]
+          metadata[:stream_type] = @stream.class.name
+          if @stream.respond_to?(:stream)
+            metadata[:stream_inner_type] = @stream.stream.class.name
+            metadata[:stream_file_path] = @stream.stream.to_path if @stream.stream.respond_to?(:to_path)
+          end
+        end
+
+        if env
+          metadata[:api_format] = env[Grape::Env::API_FORMAT]
+          metadata[:content_type] = env['CONTENT_TYPE']
+        end
+
+        metadata
+      end
+    end
+  end
+end

lib/grape/endpoint.rb

@@ -8,6 +8,7 @@ module Grape
   class Endpoint
     extend Forwardable
     include Grape::DSL::Settings
+    include Grape::DSL::BodyMetadata
     include Grape::DSL::Headers
     include Grape::DSL::InsideRoute
 
@@ -80,7 +81,7 @@ def initialize(new_settings, options = {}, &block)
       if block
         @source = block
         @block = lambda do |endpoint_instance|
-          ActiveSupport::Notifications.instrument('endpoint_render.grape', endpoint: endpoint_instance) do
+          ActiveSupport::Notifications.instrument('endpoint_render.grape', endpoint: endpoint_instance, body_metadata: endpoint_instance.extract_endpoint_body_metadata) do
             endpoint_instance.instance_exec(&block)
           rescue LocalJumpError => e
             Grape.deprecator.warn 'Using `return` in an endpoint has been deprecated.'
@@ -218,7 +219,7 @@ def inspect
     protected
 
     def run
-      ActiveSupport::Notifications.instrument('endpoint_run.grape', endpoint: self, env: env) do
+      ActiveSupport::Notifications.instrument('endpoint_run.grape', endpoint: self, env: env, body_metadata: extract_endpoint_body_metadata) do
         @request = Grape::Request.new(env, build_params_with: namespace_inheritable(:build_params_with))
         begin
           self.class.run_before_each(self)
@@ -272,7 +273,7 @@ def lazy_initialize!
     def run_validators(validators, request)
       validation_errors = []
 
-      ActiveSupport::Notifications.instrument('endpoint_run_validators.grape', endpoint: self, validators: validators, request: request) do
+      ActiveSupport::Notifications.instrument('endpoint_run_validators.grape', endpoint: self, validators: validators, request: request, body_metadata: extract_endpoint_body_metadata) do
         validators.each do |validator|
           validator.validate(request)
         rescue Grape::Exceptions::Validation => e
@@ -288,7 +289,7 @@ def run_validators(validators, request)
     end
 
     def run_filters(filters, type = :other)
-      ActiveSupport::Notifications.instrument('endpoint_run_filters.grape', endpoint: self, filters: filters, type: type) do
+      ActiveSupport::Notifications.instrument('endpoint_run_filters.grape', endpoint: self, filters: filters, type: type, body_metadata: extract_endpoint_body_metadata) do
         filters&.each { |filter| instance_eval(&filter) }
       end
       post_extension = DSL::InsideRoute.post_filter_methods(type)

lib/grape/middleware/formatter.rb

@@ -38,7 +38,10 @@ def build_formatted_response(status, headers, bodies)
         else
           # Allow content-type to be explicitly overwritten
           formatter = fetch_formatter(headers, options)
-          bodymap = ActiveSupport::Notifications.instrument('format_response.grape', formatter: formatter, env: env) do
+          bodymap = ActiveSupport::Notifications.instrument('format_response.grape',
+                                                            formatter: formatter,
+                                                            env: env,
+                                                            body_metadata: extract_body_metadata(bodies, status, headers)) do
             bodies.collect { |body| formatter.call(body, env) }
           end
           Rack::Response.new(bodymap, status, headers)
@@ -145,6 +148,28 @@ def format_from_header
         media_type = Rack::Utils.best_q_match(accept_header, mime_types.keys)
         mime_types[media_type] if media_type
       end
+
+      def extract_body_metadata(bodies, status, headers)
+        metadata = {
+          is_stream: bodies.is_a?(Grape::ServeStream::StreamResponse),
+          status: status,
+          content_type: headers[Rack::CONTENT_TYPE] || content_type_for(env[Grape::Env::API_FORMAT]),
+          format: env[Grape::Env::API_FORMAT],
+          has_entity_body: !Rack::Utils::STATUS_WITH_NO_ENTITY_BODY.include?(status)
+        }
+
+        if bodies.is_a?(Grape::ServeStream::StreamResponse)
+          metadata[:stream_type] = bodies.stream.class.name
+          # For file streams, we can get the path without reading content
+          metadata[:file_path] = bodies.stream.to_path if bodies.stream.respond_to?(:to_path)
+        else
+          # For regular bodies (Array), provide count and types without reading content
+          metadata[:body_count] = bodies.respond_to?(:size) ? bodies.size : 1
+          metadata[:body_types] = bodies.respond_to?(:map) ? bodies.map { |x| x.class.name } : [bodies.class.name]
+        end
+
+        metadata
+      end
     end
   end
 end