I have frequently encountered the following Error R14 (Memory quota exceeded) in the logs while running Grails apps on Heroku on the 1x Dyno which only allows 512mb of RAM:

2014-05-08T04:46:48.294887+00:00 heroku[web.1]: Process running mem=557M(108.9%)
2014-05-08T04:46:48.295268+00:00 heroku[web.1]: Error R14 (Memory quota exceeded)

To debug the issue and to be sure I was not having an application specific error, I created a new Grails application and followed the “Getting Started with Grails on Heroku” tutorial, but I still was getting the R14 error with a new application. To debug how much memory was being used, I used the Application Info plugin and ran the new application on Heroku. The source for this application can be found on Github.

I tried to run the same build and server process as Heroku locally but found about a 100mb difference in memory usage. The only difference I had locally was using JDK7. So, I configured the project to use JDK7 on Heroku by add adding a “system.properties” file to the project with the JDK configuration as described in the Heroku Grails tutorial:

#system.properties
java.runtime.version=1.7

After starting up with the new JDK, I no longer say the Error R14 in the logs.

Using JDK7 on Heroku, the Grails application used much less memory on startup (454 vs 582 mb) and under load (496 vs 643 mb) using Apache Bench.