coyote-workshop
loom
coyote-workshop | loom | |
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1 | 14 | |
7 | 1,901 | |
- | 3.6% | |
10.0 | 6.8 | |
almost 2 years ago | 18 days ago | |
C# | Rust | |
MIT License | MIT License |
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coyote-workshop
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Turmoil, a framework for developing and testing distributed systems
My team used Coyote to test their distributed service against network race conditions. It requires a little bit of setup to ensure all components that typically run on separate machines can run in a single process, and inter-process communication happens through interfaces that can be stubbed out during testing.
I designed a series of workshops to teach these ideas internally at Microsoft. You can find the source code used in the workshop at https://github.com/microsoft/coyote-workshop - the repo can use better README files but sharing it nonetheless in case the setup helps inspire your own use of Coyote.
loom
- Turmoil, a framework for developing and testing distributed systems
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An Introduction to Lockless Algorithms
> Mutexes are very cheap in the uncontended case
It was a while ago I was deep into this mess so forgive any ignorance–but–iirc the thread-mutex dogma[1] has many pitfalls despite being so widely used. Primarily they’re easy to misuse (deadlocks, holding a lock across a suspend point), and have unpredictable performance because they span so far into compiler, OS and CPU territory (instruction reordering, cache line invalidation, mode switches etc). Also on Arm it’s unclear if mutices are as cheap because of the relaxed memory order(?). Finally code with mutices are hard to test exhaustively, and are prone to heisenbugs.
Now, many if not most of the above apply to anything with atomics, so lock-free/wait-free won’t help either. There’s a reason why a lot of concurrency is ~phd level on the theoretical side, as well as deeply coupled with the gritty realities of hardware/compilers/os on the engineering side.
That said, I still think there’s room for a slightly expanded concurrency toolbox for mortals. For instance, a well implemented concurrent queue can be a significant improvement for many workflows, perhaps even with native OS support (io_uring style)?. Another exciting example is concurrency permutation test frameworks[2] for atomics that reorder operations in order to synthetically trigger rare logical race conditions. I’ve also personally had great experience with the Golang race detector. I hope we see some convergence on some of this stuff within a few years. Concurrency is still incredibly hard to get right.
[1]: I say this only because CS degrees has preached mutices to as the silver bullet for decades.
[2]: https://github.com/tokio-rs/loom
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Should atomics be unsafe?
Of course atomics are absolutely essential for some of the libraries we take for granted, such as Arc and Tokio. But if you start reading the code and comments and issues and PRs around code like that, you'll see how much work it took to mature them to the point we can now rely on them. That's why tools like Loom exist.
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Best tool to find deadlocks (in async code)
loom and shuttle can help you narrow down the problem.
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Does Rust not need extra linting and sanitizing tools like C++?
Unless you are writing unsafe code, you generally don't need to use sanitizers. If you do write unsafe code, checking it with a sanitizer would be a great idea. Two most useful tools here I think are miri and loom.
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The Deadlock Empire
https://github.com/tokio-rs/loom perhaps? It also models weak memory reordering, but takes some work to integrate into existing apps.
For triggering race conditions in compiled binaries, you could try https://robert.ocallahan.org/2016/02/introducing-rr-chaos-mo....
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What could Go wrong with a mutex? (A Go profiling story)
There is Loom[1] (part of the Tokio project) for exhaustively testing multithreaded code. Though as far as I can tell it is designed for debugging threads, not async tasks.
[1] https://github.com/tokio-rs/loom
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Cooptex - Deadlock-free Mutexes
That tool seems similar to https://github.com/tokio-rs/loom, insofar as detecting potential locking errors. These are useful during development, but could still miss production cases (as dev never perfectly matches production). This crate is meant to not have to worry about possibly deadlocking.
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A bug that doesn’t exist on x86: Exploiting an ARM-only race condition
Rust doesn't catch memory ordering errors, which can result in behavioral bugs in safe Rust and data races and memory unsafety in unsafe Rust. But Loom is an excellent tool for catching ordering errors, though its UnsafeCell API differs from std's (and worse yet, some people report Loom returns false positives/negatives in some cases: https://github.com/tokio-rs/loom/issues/180, possibly https://github.com/tokio-rs/loom/issues/166).
- Multicore OCaml: April 2021
What are some alternatives?
shadow - Shadow is a discrete-event network simulator that directly executes real application code, enabling you to simulate distributed systems with thousands of network-connected processes in realistic and scalable private network experiments using your laptop, desktop, or server running Linux.
eioio - Effects-based direct-style IO for multicore OCaml
fast-caspaxos - Fast CASPaxos: Fast Paxos optimizations applies to CASPaxos for 1RTT multi-leader commit
console - a debugger for async rust!
ocaml-multicore - Multicore OCaml
shuttle - Shuttle is a library for testing concurrent Rust code
TLAPLUS_DeadlockEmpire - Specs and models for solving the DeadlockEmpire problems using TLA+ and TLC
triple-buffer - Implementation of triple buffering in Rust
Rudra - Rust Memory Safety & Undefined Behavior Detection
ocaml-aeio - Asynchronous effect based IO
miri - An interpreter for Rust's mid-level intermediate representation
MIRAI - Rust mid-level IR Abstract Interpreter