5 ms·

Given Project Loom hasn't been available, how does it utilise Virtual Threads already?

oweiler 4y ago
Project Loom is in preview, and far from available. As far as I can see, Javalin doesn't make use of virtual threads yet.
- tipsee 4y ago
  It does :) We use reflection to build the Virtual Thread Factory if the user has Loom enabled in their enviroment: https://github.com/javalin/javalin/blob/master/javalin/src/main/java/io/javalin/util/ConcurrencyUtil.kt#L32-L91 https://github.com/javalin/javalin/blob/master/javalin/src/m...
- pron 4y ago
  Virtual threads are already available in the current version of the JDK (19) as a Preview feature. Because it's not a preview language feature but a preview API, libraries can use it without compiling with --enable-preview, either with reflection or by having the application supply a virtual thread ThreadFactory, which means they can make use of virtual threads if the application turns preview features on. Preview language features are different as they require compiling with --enable-preview, which creates a "poisoned" class file that cannot be loaded at all without preview enabled, so preview language features are not recommended for use by libraries, but preview APIs are fine (see JEP 12: Preview Features https://openjdk.org/jeps/12 https://openjdk.org/jeps/12).
tipsee 4y ago
If you run this on JDK19 with *--enable-preview*, Javalin will use Virtual Threads for the Server ThreadPool (as well as all other ThreadPools it has).
- daveidol 4y ago
  How does it compare to coroutines in Kotlin?
  - tipsee 4y ago
    I mean, it sort of doesn't? Coroutines is a whole concept, Virtual Threads can in most cases just replace java.lang.Threads, which is how it's implemented in Javalin. We just swap out the OS Threads for Virtual Threads.
  - stefs 4y ago
    i'd be interested in this too. my guess: virtual threads are slightly more memory efficient and slightly faster, but same ballpark.
    - stefs 4y ago
      now that i think about it i'm pretty sure my guess is completely wrong. memory usage (and thus concurrent-inactives) might be similar, but i expect the virtual threads to be much more efficient.
      - stefs 4y ago
        except if you use the appropriate non-blocking methods! with blocking io, kotlin coroutines are just running in a thread pool.

Project Loom is in preview, and far from available. As far as I can see, Javalin doesn't make use of virtual threads yet.

tipsee 4y ago
It does :) We use reflection to build the Virtual Thread Factory if the user has Loom enabled in their enviroment: https://github.com/javalin/javalin/blob/master/javalin/src/main/java/io/javalin/util/ConcurrencyUtil.kt#L32-L91 https://github.com/javalin/javalin/blob/master/javalin/src/m...
pron 4y ago
Virtual threads are already available in the current version of the JDK (19) as a Preview feature. Because it's not a preview language feature but a preview API, libraries can use it without compiling with --enable-preview, either with reflection or by having the application supply a virtual thread ThreadFactory, which means they can make use of virtual threads if the application turns preview features on. Preview language features are different as they require compiling with --enable-preview, which creates a "poisoned" class file that cannot be loaded at all without preview enabled, so preview language features are not recommended for use by libraries, but preview APIs are fine (see JEP 12: Preview Features https://openjdk.org/jeps/12 https://openjdk.org/jeps/12).

tipsee 4y ago

If you run this on JDK19 with *--enable-preview*, Javalin will use Virtual Threads for the Server ThreadPool (as well as all other ThreadPools it has).

daveidol 4y ago
How does it compare to coroutines in Kotlin?
- tipsee 4y ago
  I mean, it sort of doesn't? Coroutines is a whole concept, Virtual Threads can in most cases just replace java.lang.Threads, which is how it's implemented in Javalin. We just swap out the OS Threads for Virtual Threads.
- stefs 4y ago
  i'd be interested in this too. my guess: virtual threads are slightly more memory efficient and slightly faster, but same ballpark.
  - stefs 4y ago
    now that i think about it i'm pretty sure my guess is completely wrong. memory usage (and thus concurrent-inactives) might be similar, but i expect the virtual threads to be much more efficient.
    - stefs 4y ago
      except if you use the appropriate non-blocking methods! with blocking io, kotlin coroutines are just running in a thread pool.