Current NEWRELIC_DISPACHER default value is not works in Rails 4.2 with Puma, New Relic on Heroku. Not works: $ heroku config:add NEWRELIC_DISPACHER=puma Works: $ heroku config:add NEWRELIC_DISPACHER=Puma So I have updated default value.
With queue_requests set to true (the default), workers accept all requests and queue them before passing them to the handlers. With it set to false, each worker process accepts exactly as many requests as it is configured to simultaneously handle. In combination with threads 1, 1 this ensures that requests are balanced across workers in a single threaded application. This can avoid deadlocks when a single threaded app sends a request to itself. (For example, to generate a PDF.)