If you have a codebase using a reactive framework and want to switch to virtual threads, you can start by configuring the reactive framework to use virtual threads itself using Executors.newVirtualThreadPerTaskExecutor() or similar. This is not necessary for a top-down approach as long as the blocking code runs in virtual threads. Virtual threads represent a lighter-weight approach to multi-threaded applications than the traditional Java model, which uses one thread of execution per application request. Project Loom features that reached their second preview and incubation stage, respectively, in Java 20 included virtual threads and structured concurrency. Previews are for features set to become part of the standard Java SE language, while incubation refers to separate modules such as APIs.
- More importantly, you can actually see, what is the amount of CPU consumed by each and every of these threads?
- When these features are production ready, it should not affect regular Java developers much, as these developers may be using libraries for concurrency use cases.
- These mechanisms are not set in stone yet, and the Loom proposal gives a good overview of the ideas involved.
- But rather to introduce this powerful paradigm that will greatly (in Oracle’s words “dramatically”) reduce the effort of creating very high scale concurrent workflows in Java.
- It’s absolutely fine to start 10,000 concurrent connections, because you won’t pay the price of 10,000 carrier or kernel threads, because these virtual threads will be hibernated anyway.
- Conveniently you can store some data in the entry point of the request handler and use that data all across the workload of the request being executed without having to explicitly pass that data as a method argument across your codebase.
- These virtual threads actually reside on heap, which means they are subject to garbage collection.
At least that’s what we might think, you no longer need reactive programming and all these like WebFluxes, RxJavas, Reactors, and so on. This piece of code is quite interesting, because what it does is it calls yield function. It voluntarily says that it no longer wishes to run because we asked that thread to sleep. Unparking or waking up means basically, that we would like ourselves to be woken up after a certain period of time.
New methods in Thread Class
That’s the problem that’s already handled by platform threads or kernel threads because they do support preemption, so stopping a thread in some arbitrary moment in time. Much digital ink has already been spilled on this subject, and the consensus loom java appears to be “probably not”. Here’s another code snippet of the carrier threads. The API may change, but the thing I wanted to show you is that every time you create a virtual thread, you’re actually allowed to define a carrierExecutor.
I’m experimenting with Project Loom for quite some time already. QCon Plus is a virtual conference for senior software engineers and architects that covers the trends, best practices, and solutions leveraged by the world’s most innovative software organizations. Tomasz Nurkiewicz works in the e-commerce sector. Involved in open-source, DZone’s Most Valuable Blogger, used to be very active on StackOverflow. Author, trainer, conference speaker, technical reviewer, runner. Claims that code not tested automatically is not a feature but just a rumor.
Java Project Loom
Java 20 contained five more major JDK enhancement proposal updates under Projects Loom, Amber and Panama, and a few other Project Amber features were discussed as future roadmap items for Java 21. Overall, none of Java 20’s features were “earth-shattering,” according to Andrew Cornwall, an analyst at Forrester Research, but all stand to play an important role in updating Java for the 21st century. If they do, they could help the mature Java language keep up with newer web applications, said Marcus Hellberg, vice president of developer relations at Vaadin, makers of a Java web development framework based in Finland. Selecting a pattern or using a banner pattern on the list shows the preview of the banner after applying, if a dye is present. To finish, the player must take the banner in the slot beneath the preview.
Other than code simplicity, what’s really powerful here is a unified way of handing error scenarios of different executions running in the completely different (virtual or platform) threads. Conveniently you can store some data in the entry point of the request handler and use that data all across the workload of the request being executed without having to explicitly pass that data as a method argument across your codebase. Almost every blog post on the first page of Google surrounding JDK 19 copied the following text, describing virtual threads, verbatim. By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.
Loom and the future of Java
Meaning if you are fully familiar with stuff introduced in 19 you’ll not see anything new in the coming paragraphs. Scoped values feature was directly inspired by the Lisp dialects that provide support for dynamically scoped variables, hence its syntax might be a bit different than many will expect in “traditional” Java code. However, forget about automagically scaling up to a million of private threads in real-life scenarios without knowing what you are doing. The problem with real applications is them doing silly things, like calling databases, working with the file system, executing REST calls or talking to some sort of queue/stream. However, operating systems also allow you to put sockets into non-blocking mode, which return immediately when there is no data available.
Still, a different mindset was required for using asynchronous I/O as hiding the complexity cannot be a permanent solution and would also restrict users from any modifications. Although JavaRX is a powerful and potentially high-performance approach to concurrency, it is not without drawbacks. In particular, it is quite different from the existing mental constructs that Java developers have traditionally used. Also, JavaRX can’t match the theoretical performance achievable by managing virtual threads at the virtual machine layer.
Java 17 Features: Pattern Matching for switch and Sealed Classes
With Project Loom, you no longer consume the so-called stack space. The virtual threads that are not running at the moment, which is technically called pinned, so they are not pinned to a carrier thread, but they are suspended. These virtual threads actually reside on heap, which means they are subject to garbage collection.
The call to run(…) binds the scoped value, providing an incarnation that is specific to the current thread, and then executes the lambda expression passed as argument. During the lifetime of the run(…) call, the lambda expression, or any method called directly or indirectly from that expression, can read the scoped value via the value’s get() method. After the run(…) method finishes, the binding is destroyed. A good example of data you would like to store per request / per thread, access from different points in code, and destroy when the thread gets destroyed is the user that initiated the web request. And yes, it’s this type of I/O work where Project Loom will potentially shine. Even though good,old Java threads and virtual threads share the name…Threads, the comparisons/online discussions feel a bit apple-to-oranges to me.
Project Loom: Revolution in Java Concurrency or Obscure Implementation Detail?
In order to do this, you would start rewriting reactive code that doesn’t depend on other reactive code and change the calling code to treat it like non-reactive code (while making sure it runs in virtual threads). If you are doing the actual debugging, so you want to step over your code, you want to see, what are the variables? Because when your virtual thread runs, it’s https://www.globalcloudteam.com/ a normal Java thread. It’s a normal platform thread because it uses carrier thread underneath. However, you just have to remember on the back of your head, that there is something special happening there, that there is a whole variety of threads that you don’t see, because they are suspended. As far as JVM is concerned, they do not exist, because they are suspended.
Instead, the task is pulled from the tail of the deque. Each one is a stage, and the resultant CompletablFuture is returned back to the web-framework. Let’s rewrite this processing test, this time with a bunch of threads, and this is first case, we’re going all out, not limiting the number of threads we use for the processing. This uses the newThreadPerTaskExecutor with the default thread factory and thus uses a thread group. When I ran this code and timed it, I got the numbers shown here.
How do we deal with blocking calls in Reactor?
For that, you could (since you are in a virtual thread) run some reactive operation and block for the final result of the operation. You can then later continue rewriting the reactive code that has been called by the reactive operation when no other reactive code is using this operation (all code calling the operation has been rewritten to virtual threads). How you are migrating from reactive code to virtual threads depends on you and your project. If your project is modularized properly, then it would probably be a good idea to choose the modularized approach and migrate one module after the other. With Project Loom, we simply start 10,000 threads, each thread per each image. Using the structured concurrency, it’s actually fairly simple.
