Why am I getting memory quota exceeded errors on Heroku even while unused? (play2/scala)

Question

Just sitting with no requests, I get memory keeps on increasing, eventually to memory quota exceeded. There are multiple things I don't understand. - Why memory use keeps increasing when no requests? - Where does the value of "Process running mem" come from (does not seem to be a sum of any combination of numbers from the Heap and Non-Heap usage that I can tell). - Why does it exceed even though I have the recommended `JAVA_OPTS: -Xmx384m -Xss512k -XX:+UseCompressedOops -javaagent:heroku-javaagent-1.2.jar=stdout=true`? Here is a sample of the log file ``` app/web.1: heroku-javaagent: JVM Memory Usage (Heap): used: 275M committed: 349M max:349M app/web.1: heroku-javaagent: JVM Memory Usage (Non-Heap): used: 37M committed: 37M max:219M app/web.1: heroku-javaagent: JVM Threads : total: 37 daemon: 7 non-daemon: 21 internal: 9 app/web.1: heroku-javaagent: JVM Memory Usage (Heap): used: 276M committed: 349M max:349M app/web.1: heroku-javaagent: JVM Memory Usage (Non-Heap): used: 37M committ…

Accepted Answer

This issue should not be specific to Heroku and should (ideally) be able to be reproduced locally. First, I would recommend running your app locally the same way Heroku runs it:

- Run `sbt clean compile stage` to create the `target/start` launcher

- Launch your app with `target/start -Dhttp.port=$PORT $JAVA_OPTS` (set PORT to whatever you want)

Then I would use a memory profiler, such as VisualVM, to attach to your app running locally to see what's going on.

If this does not work or you'd like to get a better breakdown of the memory usage on Heroku, I'd recommend enabling log-runtime-metrics. This can also be used with Log2Viz to get a realtime memory visualizations.

Why am I getting memory quota exceeded errors on Heroku even while unused? (play2/scala)

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