`JAVA_TOOL_OPTIONS` supports in Heroku

# `JAVA_TOOL_OPTIONS` supports in Heroku [TOC] ###### tags: `heroku` `java` --- ## About JAVA_TOOL_OPTIONS You can override these settings in the `Procfile` command (which takes precedence over the defaults). For example, to change the default of `-Xmx300m`, you could pass in: ``` web: java -Xms150M -jar target/myapp.jar ``` When a Java process is started on your dyno, the following Java options will be added to JAVA_TOOL_OPTIONS and automatically picked up by Java: - `-Dfile.encoding=UTF-8` - `-XX:+UseContainerSupport` (for Java 11 and higher) ## Adjusting Environment for a Dyno Size When a new dyno type is selected, the following settings are ~~automatically~~ added to `JAVA_TOOL_OPTIONS`: - `free`, `hobby` or `standard-1x`: **`-Xmx300m -Xss512k -XX:CICompilerCount=2`** - `standard-2x`: **`-Xmx671m -XX:CICompilerCount=2`** - `performance-m`: **`-Xmx2g`** - `performance-l`: **`-Xmx12g`** For Private Space dynos, the values are: - `private-s`: **`-Xmx671m -XX:CICompilerCount=2`** - `private-m`: **`-Xmx2g`** - `private-l`: **`-Xmx12g`** ## Monitoring Resource Usage Additional JVM flags can be used to monitor resource usage in a dyno. The following flags are **recommended for monitoring resource usage**: ``` -XX:+PrintGCDetails -XX:+PrintGCDateStamps -XX:+PrintTenuringDistribution -XX:+UseConcMarkSweepGC ``` See the [troubleshooting article](https://devcenter.heroku.com/articles/java-memory-issues "Troubleshooting Memory Issues in Java Applications") for more information about tuning a JVM process. ## Reference - [Heroku Java Support](https://devcenter.heroku.com/articles/java-support)