Spring boot, многопоточка и магия вне хогвартса

Всем привет! Меня зовут Алексей, и я работаю Java‑разработчиком с 2018 года. В статье расскажу, как столкнулся с проблемой обработки MultipartFile в многопоточном режиме. Почему эта проблема возникает и какие решения существуют. Изначально стояла задача организовать фоновую обработку Excel-файлов: принимать файл, мгновенно возвращать клиенту HTTP-200 (без данных), а обработку содержимого выполнять асинхронно в отдельном потоке. Вроде задачка тривиальная. Делаем контроллер:

https://habr.com/ru/companies/rostelecom/articles/928016/

Worker Threads in Node.js: A Complete Guide for Multithreading in JavaScript, by @nodesource.bsky.social:

https://nodesource.com/blog/worker-threads-nodejs-multithreading-in-javascript

Как обобрать дерево в несколько потоков?

Всем привет, меня зовут Антон, я Java‑разработчик в Сбере, подразделение SberWorks. Я разрабатываю Giga IDE — новую IDE на основе IntelliJ IDEA. В ходе работы столкнулся с тем, что при открытии проектов происходит сканирование всех папок для поиска тех или иных файлов. Если обобщить, то задача сводится к обходу дерева. Я решил подробнее рассмотреть эту тему, причём с прицелом на многопоточность. Задача обхода деревьев далеко не нова, существуют два основных подхода: обход в ширину и глубину. В первом случае удобно применять рекурсивный алгоритм, а во втором — понадобится дополнительная коллекция, в которую будут складываться узлы дерева, но всё это в один поток, а я решил рассмотреть эту задачу в многопоточной интерпретации.

https://habr.com/ru/companies/sberbank/articles/921528/

Link: https://mediatum.ub.tum.de/?id=601795 (It took digging to find this from the Wikipedia article [1] and the unsecured HTTP homepage for "BMDFM".)

```bibtex
@phdthesis{dissertation,
author = {Pochayevets, Oleksandr},
title = {BMDFM: A Hybrid Dataflow Runtime Parallelization Environment for Shared Memory Multiprocessors},
year = {2006},
school = {Technische Universität München},
pages = {170},
language = {en},
abstract = {To complement existing compiler-optimization methods we propose a programming model and a runtime system called BMDFM (Binary Modular DataFlow Machine), a novel hybrid parallel environment for SMP (Shared Memory Symmetric Multiprocessors), that creates a data-dependence graph and exploits parallelism of user application programs at run time. This thesis describes the design and provides a detailed analysis of BMDFM, which uses a dataflow runtime engine instead of a plain fork-join runtime library, thus providing transparent dataflow semantics on the top virtual machine level. Our hybrid approach eliminates disadvantages of the parallelization at compile-time, the directive based paradigm and the dataflow computational model. BMDFM is portable and is already implemented on a set of available SMP platforms. The transparent dataflow paradigm does not require parallelization and synchronization directives. The BMDFM runtime system shields the end-users from these details.},
keywords = {Parallel computing;Shared memory multiprocessors;Dataflow;Automatic Parallelization},
note = {},
url = {https://mediatum.ub.tum.de/601795},
}
```

[1]: https://en.wikipedia.org/wiki/Binary_Modular_Dataflow_Machine

I'm putting a talk together about #programming Mandelbrot image generator with insight into profiling and optimisation. Main part will be normal optimisations, #simd, #multithreading, and possibly gpu acceleration.

I'll also show micro benchmarking, hotspot/perf, intel advisor, and also inspecting assembly code.

Any other interesting bits I should look into putting into my talk?

Multithreading in JavaScript With Web Workers, by @honeybadger:

https://www.honeybadger.io/blog/javascript-web-workers-multithreading/

Vediamo le funzionalità del Fortran introdotte nel 2008, con i CoArray, e nel 2018 per scoprire come si possono sfruttare tutti i core delle nostre CPU abbreviando i tempi di calcoli scientifici complessi. #fortran #parallelcomputing #multithreading
https://www.youtube.com/watch?v=78_12a89MWQ

Samchika – A Java Library for Fast, Multithreaded File Processing

https://github.com/MayankPratap/Samchika

Advanced Java Multithreading Patterns for High-Performance Applications

#java #multithreading

https://dev.to/aaravjoshi/advanced-java-multithreading-patterns-for-high-performance-applications-1ola

Java exception of the day: FileAlreadyExistsException on

Files.copy(body, requestedFile, StandardCopyOption.REPLACE_EXISTING);

It is not as weird if we take into account multiple threads. From the JDK code of Files.copy after deleting the requestedFile first:

} catch (FileAlreadyExistsException x) {
... other stuff deleted ...
// someone else won the race and created the file
throw x;
}

Параллельный цикл на worker. Многопоточность JS

Как применить worker для ускорения параллельных вычислений на JS. Постарался подробно и понятно разобрать как работают worker, как общаться с ними. Показал пример многопоточного вычисления значений массива и сравнил производительность различных методов обработки массивов.

https://habr.com/ru/articles/900488/

Multi-threading is always the wrong design

https://unetworkingab.medium.com/multi-threading-is-always-the-wrong-design-a227be57f107

Exploring Ruby Ractors – I paid for for 10 cores I'm gonna use 10 cores

https://jpterry.com/posts/2025/03/exploring-ruby-ractors/

The case of the critical section that let multiple threads enter a block of code

https://devblogs.microsoft.com/oldnewthing/20250321-00/?p=110984

#FluidX3D #CFD v3.2 is out! I've implemented the much requested #GPU summation for object force/torque; it's ~20x faster than #CPU #multithreading.
Horizontal sum in #OpenCL was a nice exercise - first local memory reduction and then hardware-supported atomic floating-point add in VRAM, in a single-stage kernel. Hammering atomics isn't too bad as each of the ~10-340 workgroups dispatched at a time does only a single atomic add.
Also improved volumetric #raytracing!
https://github.com/ProjectPhysX/FluidX3D/releases/tag/v3.2

Surely it’s not a multithreaded issue?
No, it’s definitely not.

It an multithreading was issue.

FLAC 1.5 : l’encodage multithread est enfin disponible https://goodtech.info/flac-1-5-lencodage-multithread-est-enfin-disponible #codec #musique #open_source #multithreading #encodage #flac #compression #opensource #audio

Remember when I mentioned we had ported our #fire propagation #cellularAutomaton from #Python to #Julia, gaining performance and the ability to parallelize more easily and efficiently?

A couple of days ago we had to run another big batch of simulations and while things progressed well at the beginning, we saw the parallel threads apparently hanging one by one until the whole process sat there doing who know what.

Our initial suspicion was that we had come across some weird #JuliaLang issue with #multithreading, which seemed to be confirmed by some posts we found on the Julia forums. We tried the workarounds suggested there, to no avail. We tried a different number of threads, and this led to the hang occurring after a different percent completion. We tried restarting the simulations skipping the ones already done. It always got stuck at the same place (for the same number of threads).

So, what was the problem?

1/n