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Java Options Framework

The Java Options Framework contributes arbitrary Java options to the application at runtime.

Detection Criterion java_opts set in the config/java_opts.yml file or the JAVA_OPTS environment variable set
Tags java-opts

Tags are printed to standard output by the buildpack detect script


For general information on configuring the buildpack, including how to specify configuration values through environment variables, refer to Configuration and Extension.

The framework can be configured by creating or modifying the config/java_opts.yml file in the buildpack fork.

Name Description
from_environment Whether to append the value of the JAVA_OPTS environment variable to the collection of Java options
java_opts The Java options to use when running the application. All values are used without modification when invoking the JVM. The options are specified as a single YAML scalar in plain style or enclosed in single or double quotes.

Any JAVA_OPTS from either the config file or environment variables that configure memory options will cause deployment to fail as they're not allowed. Memory options are configured by the buildpack and may not be modified.

Any JAVA_OPTS from either the config file or environment variables will be specified in the start command after any Java Opts added by other frameworks.

Escaping strings

Java options will have special characters escaped when used in the shell command that starts the Java application but the $ and \ characters will not be escaped. This is to allow Java options to include environment variables when the application starts.

cf set-env my-application JAVA_OPTS '-Dexample.port=$PORT'

If an escaped $ or \ character is needed in the Java options they will have to be escaped manually. For example, to obtain this output in the start command.


From the command line use;

cf set-env my-application JAVA_OPTS '-Dexample.other=something.\\\\\$dollar.\\\\\\\slash'

From the config/java_opts.yml file use;

from_environment: true
java_opts: '-Dexample.other=something.\\$dollar.\\\\slash'

Finally, from the applications manifest use;

    JAVA_OPTS: '-Dexample.other=something.\\\\\$dollar.\\\\\\\slash'


# JAVA_OPTS configuration
from_environment: false
java_opts: -Xloggc:$PWD/beacon_gc.log -verbose:gc

Memory Settings

The following JAVA_OPTS are restricted and will cause the application to fail deployment.

  • -Xms
  • -Xmx
  • -Xss
  • -XX:MaxMetaspaceSize
  • -XX:MaxPermSize
  • -XX:MetaspaceSize
  • -XX:PermSize

Allowed Memory Settings

Setting any of the allowed memory settings may require a change to the Memory Weightings. Where a value is shown it is the default value for that setting.

Argument Description
-Xmn <SIZE> Maximum size of young generation, known as the eden region. This could effect the total heap size Memory Weightings.
-XX:+UseGCOverheadLimit Use a policy that limits the proportion of the VM's time that is spent in GC before an java.lang.OutOfMemoryError error is thrown.
-XX:+UseLargePages Use large page memory. For details, see Java Support for Large Memory Pages.
-XX:-HeapDumpOnOutOfMemoryError Dump heap to file when java.lang.OutOfMemoryError is thrown.
-XX:HeapDumpPath=<PATH> Path to directory or filename for heap dump.
-XX:LargePageSizeInBytes=<SIZE> Sets the large page size used for the Java heap.
-XX:MaxDirectMemorySize=<SIZE> Upper limit on the maximum amount of allocatable direct buffer memory. This could effect the Memory Weightings.
-XX:MaxHeapFreeRatio=<RATIO> Maximum percentage of heap free after GC to avoid shrinking.
-XX:MaxNewSize=<SIZE> Maximum size of new generation. Since 1.4, MaxNewSize is computed as a function of NewRatio. This could effect the total heap size Memory Weightings.
-XX:MinHeapFreeRatio=<RATIO> Minimum percentage of heap free after GC to avoid expansion.
-XX:NewRatio=<RATIO> Ratio of old/new generation sizes. 2 is equal to approximately 66%.
-XX:NewSize=<SIZE> Default size of new generation. This could effect the total heap size Memory Weightings.
-XX:OnError="<CMD ARGS>;<CMD ARGS>" Run user-defined commands on fatal error.
-XX:OnOutOfMemoryError="<CMD ARGS>;<CMD ARGS>" Run user-defined commands when an java.lang.OutOfMemoryError is first thrown.
-XX:ReservedCodeCacheSize=<SIZE> Java 8 Only Maximum code cache size. Also know as -Xmaxjitcodesize. This could effect the Memory Weightings.
-XX:SurvivorRatio=<RATIO> Ratio of eden/survivor space. Solaris only.
-XX:TargetSurvivorRatio=<RATIO> Desired ratio of survivor space used after scavenge.
-XX:ThreadStackSize=<SIZE> Thread stack size. (0 means use default stack size).
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