Emit MongoDB event body as a JSON string

The MongoDB integration was the only one to pass a structured Data
object as an event body. The agent serializes that to JSON before
storing it, so the output is unchanged.

Author: unflxw

.changesets/emit-mongodb-body-as-json-string.md

@@ -0,0 +1,6 @@
+---
+bump: patch
+type: change
+---
+
+Emit the MongoDB query event body as a JSON string instead of a structured data object. The recorded query body is unchanged.

lib/appsignal/integrations/mongo_ruby_driver.rb

@@ -1,5 +1,7 @@
 # frozen_string_literal: true
 
+require "json"
+
 module Appsignal
   class Hooks
     # @!visibility private
@@ -46,11 +48,13 @@ def finish(result, event)
         store   = transaction.store("mongo_driver")
         command = store.delete(event.request_id) || {}
 
-        # Finish the event in the extension.
+        # Finish the event. The sanitized command is a (nested) Hash; emit it
+        # as a JSON string. The agent serializes structured bodies to JSON
+        # anyway, so this is equivalent output.
         transaction.finish_event(
           "query.mongodb",
           "#{event.command_name} | #{event.database_name} | #{result}",
-          Appsignal::Utils::Data.generate(command),
+          JSON.generate(command),
           Appsignal::EventFormatter::DEFAULT
         )
 

spec/lib/appsignal/integrations/mongo_ruby_driver_spec.rb

@@ -91,11 +91,11 @@
         subscriber.finish("SUCCEEDED", event)
       end
 
-      it "should finish the transaction in the extension" do
+      it "should finish the event with the command as a JSON string" do
         expect(transaction).to receive(:finish_event).with(
           "query.mongodb",
           "find | test | SUCCEEDED",
-          Appsignal::Utils::Data.generate("foo" => "?"),
+          "{\"foo\":\"?\"}",
           0
         )