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Java 21: The Nice, the Meh, and the Momentous

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Re: Java 21: The Nice, the Meh, and the Momentous

#51

Post by tantamounta »

pron wrote: post #38
tantamounta wrote: post #19

Earlier quoted context omitted.

With the API being nearly the same, I keep just thinking that Virtual Threads are basically identical to Platform Threads except that they use far less memory (so you can have lots more of them). Are there any other actual differences? Better Peformance?

The relationship between throughput, latency, and concurrency in servers is expressed via Little's theorem. If your server is written in the thread-per-request style -- the only style for which the platform offers built-in language, VM, and tooling support -- then the most important factor affecting maximum throughput is the number of threads you can have (until, of course, the hardware is fully utilised). Being able…

Thanks for the video. I feel like there's a bit of conflation between the terms "performance(latency)" and "throughput", but I see the point. I'd be interested to see that latency graph (Time marker 15:38) between platform and virtual threads in the case where the server doesn't manufacture a 100ms delay (say, in the case of a caching reverse-proxy).

Also - millions of Java programmers thank you for not going to async/await. What an evil source-code virus (among other things that is).

I tried to watch it at 1.25x speed as I normally do, but you already talk at 1.25x speed, so no need !

Re: Java 21: The Nice, the Meh, and the Momentous

#52

Post by dihrbtk »

defatigable wrote: post #33
larperdoodle wrote: post #21

Earlier quoted context omitted.

Why haven't places updated already? It's not that much work to update. Where I work we always go to the new LTS version as soon as it's supported by gradle. Doesn't cross anyone's mind to _not_ upgrade.

This is a niche case, but I spent months trying to upgrade one of our services from one LTS version to the next (I forget which). We encountered a weird bug where services running on the latest JRE would mysteriously corrupt fields when deserializing thrift messages, but only after running for a little while. After an enormously unpleasant debugging cycle, we realized that the JIT compiler was incorrectly eliminating…

did you work for a very large rideshare company by any chance?

Re: Java 21: The Nice, the Meh, and the Momentous

#53

Post by specialist »

rusk wrote: post #31
frou_dh wrote: post #4

Earlier quoted context omitted.

I really like that Ruby throws NoMatchingPatternError if none of the patterns match. It's a bit like the much-acclaimed exhaustive pattern matching in static languages (though at runtime rather than compile-time, obviously) and better than just silently falling off the end, which IIRC is what Python's pattern matching does.

In Python you can terminate a for loop with else, which will be run whenever the loop runs to the end without breaking

Neat. Will check it out.

I recently spotted a (new to me) foreach / else construct in a templating language (sorry, forget which one); else is invoked if the list is empty. Nice sugar for common outputs like "no items found".

I appreciate modest syntactic sugar.

For instance, my #1 sugar wish is for Java's foreach is to do nothing when the list reference is null. Versus tossing a NPE.

Eliminates an unnecessary null check and makes the world a little bit more null-safe.

Re: Java 21: The Nice, the Meh, and the Momentous

#54

Post by pron »

tantamounta wrote: post #51
pron wrote: post #38

Earlier quoted context omitted.

The relationship between throughput, latency, and concurrency in servers is expressed via Little's theorem. If your server is written in the thread-per-request style -- the only style for which the platform offers built-in language, VM, and tooling support -- then the most important factor affecting maximum throughput is the number of threads you can have (until, of course, the hardware is fully utilised). Being able…

Thanks for the video. I feel like there's a bit of conflation between the terms "performance(latency)" and "throughput", but I see the point. I'd be interested to see that latency graph (Time marker 15:38) between platform and virtual threads in the case where the server doesn't manufacture a 100ms delay (say, in the case of a caching reverse-proxy). Also - millions of Java programmers thank you for not going to asyn…

To understand what happens when the server doesn't perform IO, apply Little's formula to the CPU only. Clearly, the maximum concurrency would be equal to the number of cores, which means that in that situation there would be no benefit to more threads than cores. What you would see in the graph would be that the server fails once L is equal to the number of cores. The average ratio between IO and CPU time as portions of the average duration would give you an upper limit on how much more throughput you gain by having more threads. That's what I explain at 11:34.

Also, both throughput and latency are performance metrics.

Re: Java 21: The Nice, the Meh, and the Momentous

#55

Post by hibikir »

unregistereddev wrote: post #3
ecshafer wrote: post #2

Java getting better pattern matching is a great change. Id really like more of the functional features to make it into Java. I would love if Java pattern matching could at least get to the level of ruby pattern matching. Ruby pattern matching will allow you to deconstruct arrays and hashes to get pretty complicated patterns, which is really powerful. Right now it seems like Java might have that with a lambda in the p…

Pattern matching is a neat tool to keep in the toolbox. When it's the right tool for the job, it is really cool and is a lot cleaner than a bunch of conditional checks. However, I rarely reach for it. Maybe my use cases are unusual? I am genuinely curious how often other developers find pattern matching to be the best tool for the job.

Pattern matching is what makes sum types ergonomic enough to be used. Many a Java design doesn't use said interface-based sum types because it's so cumbersome to use them. But whena language has pattern matching, then suddenly designing with sum types in mind is done a lot, and therefore you see examples of good pattern matching everywhere.

When I teach Scala, a very high percentage of the teaching time is ultimately down to re-introducing how to design business domains, because seasoned devs just reach for large classes with a million optional fields, which not only can represent valid systems states, but thousands of invalid ones.

Re: Java 21: The Nice, the Meh, and the Momentous

#56

Post by specialist »

waynesonfire wrote: post #18

> Over 10,000 bug fixes Most of which were likely introduced during new feature development in recent releases. To suggest that this on its own somehow manifests a more stable jdk compared to some ancient, battle tested version of the jdk is debatable. I find it rather concerning that so many bugs exist to begin with. Why are these not caught sooner? Has the whole world gone crazy? Am I the only one around here who g…

Randomly looking at bugs fixed the last 10 weeks, it seems like a healthy mix of old and new bugs.

https://bugs.openjdk.org/browse/JDK-8316305?filter=-7&jql=pr...

Being allergic to JIRA, my JIRA-fu is weak, so there's probably an easier/faster way to report bugs fixed in v21.

Any way.

> Am I the only one around here who gives a shit about quality?

Ages ago, I was a QA/Test manager. So I appreciate your sentiment. But it seems to me that Oracle's being a FANTASTIC shepherd of Java. Definitely a huge upgrade, at the very least.

Re: Java 21: The Nice, the Meh, and the Momentous

#57

Post by doodpants »

waynesonfire wrote: post #18

> Over 10,000 bug fixes Most of which were likely introduced during new feature development in recent releases. To suggest that this on its own somehow manifests a more stable jdk compared to some ancient, battle tested version of the jdk is debatable. I find it rather concerning that so many bugs exist to begin with. Why are these not caught sooner? Has the whole world gone crazy? Am I the only one around here who g…

You might be the only person in the world who writes bug-free code on the first try.

Re: Java 21: The Nice, the Meh, and the Momentous

#60

Post by yankput »

PaulHoule wrote: post #36

(1) It's a bit of a bad smell (which he points out) that records aren't being used much at all in the Java stdlib, I wrote something that built out stubs for the 17 and 18 stdlibs and that stood out like a sore thumb. I do like using records though. (2) I've looked at other ways to extend the collections API and related things, see https://github.com/paulhoule/pidove and I think the sequenced collections could have b…

Virtual threads are strictly better than normal threads, no? I am thinking of any reason to still use traditional threads. Is there any downside?
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