Support Java 19 virtual threads [242309109]

Assigned

Feature Request

Status Update

No update yet.

Description

al...@gmail.com

created issue #1

Aug 13, 2022 11:03AM

Can you please add support for Java 19 virtual threads?

Regards

Comments

ri...@google.com <ri...@google.com> #2Aug 15, 2022 08:40AM

Added this as blocking the corresponding desugar bug in R8 (so that we get notified if this is implemented, not to indicate that this is blocking us now)

ot...@google.com <ot...@google.com> #3Aug 15, 2022 08:50AM

Hi Ali, thanks for the request.

Do you have any concrete use cases in mind for virtual threads on Android?

We are trying to align Android with the OpenJDK LTS releases: Android T is supporting a subset of OpenJDK 11 APIs, Android U will support a subset of OpenJDK 17 APIs.

JEP425 is a preview API for virtual threads, and though interesting, we don't get second chances in Android to ship APIs so we are likely to wait on a final API heading towards an OpenJDK LTS release. Virtual threads typically bring some wins for server workloads, for Android those wins may not be so clear (lots of JNI code; execution that does not look like server workloads).

ot...@google.com <ot...@google.com> Aug 16, 2022 03:04PM

Assigned to al...@gmail.com.

al...@gmail.com <al...@gmail.com> #4Aug 19, 2022 05:36AM

Do you have any concrete use cases in mind for virtual threads on Android?

Well may not be a concrete use cases. I am developing a 3D game (for Desktop and Android) using jMonkeyEngine (Java 3D game engine). I was considering to use virtual threads for asset loading and client server comunications. The point is to have a sigle code base that works on both Desktop Java and Android.

Well there are some other cool features comming to Java in the future also, like project Valhalla,... I hope to see those feature supported on Android as well when they are released. It will be a great help for us to maintains a single code base.

Kind Regards

ot...@google.com <ot...@google.com> #5Aug 19, 2022 09:41AM

Reassigned to ar...@google.com.

Thanks Ali, this is a good data point.

As you expect we follow the JEPs and some of the discussions / announcements around future Java projects.

We are limited by the need to maintain app compatibility across releases and features like virtual threads and Valhalla are large changes with deep runtime integration: we may be able to offer forward compatible implementations when they are further along (e.g. available from some API level onwards). Whether we could desugar either proposal is a challenging proposition, for example, Android doesn't have legacy APIs that would support switching between virtual threads and carrying virtual thread state outside of the runtime itself and trying to integrate with I/O would likely be cumbersome.

al...@gmail.com <al...@gmail.com> #6Aug 19, 2022 07:06PM

Yes, I understand that desugaring might be not possible for some of them. But being able to offer forward compatible implementations on future API releases is still great news.

gu...@gmail.com <gu...@gmail.com> #7Sep 27, 2022 12:24AM

It would be very beneficial for FrostWire, an open source bittorrent client that runs across different platforms, to have as much of its concurrency source code (which is common across different OSes) reduce the number of OS threads, most importantly on Android where so many devices are constrained of memory and cpu capabilities.

ji...@google.com <ji...@google.com> Oct 3, 2022 01:15PM

Reassigned to an...@google.com.

ot...@google.com <ot...@google.com> #8Oct 3, 2022 01:44PM

Thanks for the additional data point. We expect to do some evaluation of potential benefits / issues of virtual threads during the Android U timeframe. If that looks promising, we might expect an implementation for Android 16 and hopefully the upstream API will have finalised by then.

vi...@google.com <vi...@google.com> Nov 7, 2022 11:38AM

Reassigned to ot...@google.com.

ot...@google.com <ot...@google.com> Jan 16, 2023 04:33PM

Reassigned to so...@google.com.

no...@gmail.com <no...@gmail.com> #9Dec 28, 2023 08:48PM

This is absolutely needed! Virtual threads also come with continuations, which opens up entire new designs from the Java language when writing apps. Has there been any progress on this?

so...@google.com <so...@google.com> #10Dec 29, 2023 02:47PM

As per comment#8, we have done some evaluation on this and are considering the possibility of supporting virtual threads. In terms of benefits, the main one so far is having the same code base across platforms. It would be interesting to hear more about current limitations in Android that would be solved by virtual threads or continuations.

In terms of timeline, Android currently (since 14) supports Java 17. Migration to Java 21 (the next LTS) will not be complete within the next release timeframe. So, as stated in comment#8, we might have expect an implementation for the following release.