Easy to specifying JVM memory settings such as heap min/max sizes

[davsclaus]

I have looked in the documentation, jbang --help, and searched a bit on the internet, but could not find out if JBang offered a nice and easy way to specify JVM memory settings when running a script.

At Apache Camel we love JBang and are using it for Camel CLI and a new way to use Camel.

In the Camel CLI we made a command to output status of the running Camel integrations and one shows some memory and other status, eg as shown below:

  PID   NAME        JAVA     CAMEL            PLATFORM  STATUS    AGE         HEAP       NON-HEAP      GC      THREADS   CLASSES
 56699  bar.yaml    11.0.13  3.19.0-SNAPSHOT  JBang     Running  12h27m  76/322/4294 MB  59/62 MB  215ms (20)    7/9    6124/6124
 56712  chuck.yaml  11.0.13  3.19.0-SNAPSHOT  JBang     Running  12h27m  48/322/4294 MB  82/86 MB  317ms (39)    8/9    7480/7480

The heap stats are: used/committed/max
If you look then they all have 4gb as max.

I wonder if there is a way to set the min/max size ala -Xms64m -Xmx512m but maybe in an easier way? And also if these could be set in the script file itself, like you have //DEPS and whatnot (https://github.com/apache/camel/blob/main/dsl/camel-jbang/camel-jbang-main/dist/CamelJBang.java#L22).

[quintesse]

Hi @davsclaus , yes you can set compile and runtime option sin the script using //JAVAC_OPTIONS and //JAVA_OPTIONS, see https://www.jbang.dev/documentation/guide/latest/running.html#java-and-javac-options

And you can also use the command line flag --java-options for passing runtime options.

[davsclaus]

Thanks for the pointers, this is how you can do it

jbang run --java-options=-Xmx300m camel@apache/camel run bar.yaml

Setting heap sizes is more common to do, but can be a bit tricky to do.
Maybe add an example in the docs, at that link you provided.

[davsclaus]

Also the --java-options is not possible for "app" like we have with camel, so eg you cannot do

camel --java-options=-Xmx300m run bar.yaml

I don't think I have been able to add --java-options in our custom Camel JBang CLI - eg its the same when I need to enable JVM debug, then I must do

jbang run --debug camel@apache/camel run bar.yaml

[quintesse]

Indeed, right now we don't have an option to pass arguments to Jbang when using an installed "app".
The only way you could make that work is using the JBANG_JAVA_OPTIONS env var, like this (didn't test, but should work):

JBANG_JAVA_OPTIONS=-Xmx300m camel run bar.yaml

[quintesse]

I opened an issue for this: #1442