The Ruby agent has built-in instrumentation for MongoDB queries made via the mongo gem.
Supported gems
This summarizes the Ruby agent's support for gems by version.
Gem version  | Comments  | 
|---|---|
  | Supported by New Relic's Ruby agent 3.7.1 or higher  | 
  | Not supported  | 
  | Requires New Relic's Ruby agent 3.13.1 or higher  | 
Other gems  | Support for Mongoid 2/3/4 and Moped currently is available only via third-party gems. For links to the relevant projects, see extends_newrelic_rpm.  | 
Third-party and extends_newrelic_rpm instrumentation
The extends_newrelic_rpm and newrelic_mongo gems both provide basic instrumentation for mongo. New Relic does not recommend running Mongo instrumentation via these gems alongside the Ruby agent's built-in Mongo support. This might double-count metrics such as overall database time.
Also, the extends_newrelic_rpm and newrelic_mongo gems both use a distinct setting that can be used to disable them if removing those gems entirely isn't possible in your environment. For those third party gems, set disable_mongodb: false in your newrelic.yml.
Disabling instrumentation
To disable Mongo instrumentation in the agent, add the following to your newrelic.yml:
disable_mongo: true