Need docs on how to interact with the Node event loop when in JVM node

[mikehearn]

I read the docs but I still am unclear on a few things.

If I use node --jvm and my program starts in Javascript context, then I call into Java to create a Java main thread to run a Java program, how can I call back and forth between those two threads - how can I submit work to the node event loop? (a node event loop? i assume we can only have one!)

For example, assume I have a JavaFX app and I'd like to use node modules from it. AFAICT there are two ways to do this:

1. Implement the core NodeJS API on top of the JVM. Disadvantage: lots of work, may not help with modules that use native code, advantage: presumably the Node event loop could be precisely controlled e.g. integrated with a Netty or JavaFX event loop.

2. Allow Node to start up the JVM and control the main thread, start a separate thread to run my Java main method on. Advantage: works with graaljs as it is now. Disadvantage: using JS code might require a blocking call into the node event loop.

With (2), if I break the rules and use the JS in a multi-threaded way and call it on a separate non-Node thread, what happens if I lose my bet and the code wants to register a callback on the libuv event loop? Do I get an error?

Some samples and docs would go a long way here.

[wirthi]

Hi Mark,

thanks for your comment. What you request for is not possible (or rather: not officially supported) at the moment. A very similar request and some clarification was posted in #5

We do have an internal possibility to do what you request, but we have not yet published that. One reason for that is that we still hope to piggyback on the multithreading APIs that the Node community is working on, instead of publishing our own APIs. @eleinadani can give you more details on that effort if you are interested.

Thanks,
Christian

[mikehearn]

I see. Thanks for the info.

[cztomsik]

Is it possible to use hibernate-mapped objects? What would actually happen if it was lazy-loaded for example? Is that a blocking call? Or let's say HttpClient, is that blocking?

Edit: it's blocking, it's also not possible to start any new threads in graal-javascript.

[mikehearn]

This is now resolved by the publishing of a new Medium blog post.

[aslushnikov]

This is now resolved by the publishing of a new Medium blog post.

@mikehearn would you mind sharing a link?

[mikehearn]

See here:

https://blog.plan99.net/vertical-architecture-734495f129c4

and https://github.com/mikehearn/nodejs-interop