legion VS python-mysql-replication

I work on a distributed runtime system for heterogeneous supercomputers [1].

As an example of the sort of bug we regularly deal with, I am at this exact moment tracking down a freeze that occurs on 8,192 nodes of a supercomputer [2]. That means I'm using about 64,000 GPUs and about half a million CPU cores. The smallest node count I've seen my issue is 2,048 nodes and at that scale it only happens about 10% of the time.

We've been debating internally whether Antithesis could help us or not. On the one hand, the fuzzing to explore the state space, and deterministic reproduction, are exactly what we want. On the other hand, we believe our state space is much larger than what you see in a typical distributed database. (And not just because of the sheer scale of things, but even on a single node we have state machines with order hundreds to thousands of states in them.) Based on the post here and the "scenario" count explored in CouchDB, I'm not convinced you'd be able to handle us. :-)

I'd be curious what you think. Happy to discuss here, or contact info in profile.

[1]: https://legion.stanford.edu/

[2]: https://www.olcf.ornl.gov/frontier/

Parallelism in CS is a bit like security in CS. People know it matters in the abstract senses but you really only get into it if you look for the training specifically. We're getting better at both over time: just as more languages/libraries/etc. are secure by default, more now are parallel by default. There's a ways to go, but I'm glad we didn't do this prematurely, because the technology has improved a lot in the last decade. Look for example at what we can do (safely!) with Rayon in Rust vs (unsafely!) with OpenMP in C++.

And there are things even further afield like what I work on [1][2][3].

[1]: https://legion.stanford.edu/

[2]: https://regent-lang.org/

[3]: https://github.com/nv-legate/cunumeric

Chapel has at least several full-time developers at Cray/HPE and (I think) the US national labs, and has had some for almost two decades. That's much more than $100k.

Chapel is also just one of many other projects broadly interested in developing new programming languages for "high performance" programming. Out of that large field, Chapel is not especially related to the specific ideas or design goals of Mojo. Much more related are things like Codon (https://exaloop.io), and the metaprogramming models in Terra (https://terralang.org), Nim (https://nim-lang.org), and Zig (https://ziglang.org).

But Chapel is great! It has a lot of good ideas, especially for distributed-memory programming, which is its historical focus. It is more related to Legion (https://legion.stanford.edu, https://regent-lang.org), parallel & distributed Fortran, ZPL, etc.

I should also note that there is Pygion if you want to use Python. Not a lot of great reference material right now, but there's the paper:

https://legion.stanford.edu/pdfs/pygion2019.pdf

And code samples:

https://github.com/StanfordLegion/legion/tree/stable/binding...

We use PyPy for performing verification of our software stack [1], and also for profiling tools [2]. The verification tool is basically a complete reimplementation of our main product, and therefore encodes a massive amount of business logic (and therefore difficult to impossible to rewrite in another language). As with other users, we found the switch to PyPy was seamless and provides us with something like a 2.5x speedup out of the box, with (I think) higher speedups in some specific cases.

We eventually rewrote the profiler tool in Rust for additional speedups, but as mentioned for the verification engine, it's probably too complicated to ever do that so we really appreciate drop-in tools like PyPy that can speed up our code.

[1]: https://github.com/StanfordLegion/legion/blob/master/tools/l...

[2]: https://github.com/StanfordLegion/legion/blob/master/tools/l...

Legion is also doing something like that: https://legion.stanford.edu/

If you really want to dig into it you can read up on the tutorials and/or papers from the Legion project: https://legion.stanford.edu/

But briefly, these task-based programs preserve sequential semantics. That means (whatever the system actually does when running your program), as long as you follow the rules, the parallelism should be invisible to the execution of the program.

Computer Science Research Dept., SLAC National Accelerator Laboratory | Research Scientist / Engineer | Menlo Park, CA or REMOTE, VISA | Full Time

We're a research group within SLAC, headed by Alex Aiken (https://theory.stanford.edu/~aiken/). We focus on fundamental CS research that has the potential to impact science, mainly in the areas of high-performance and distributed computing, programming languages, compilers, networks, operating systems, etc. One of our major projects is Legion, a forward-looking programming system for distributed computing (https://legion.stanford.edu/). Legion has been used to create new programming languages (https://regent-lang.org/), seamless distributed NumPy (https://developer.nvidia.com/cunumeric), and a drop-in replacement for Keras and PyTorch (https://flexflow.ai/), among many other things.

We are looking for strong scientists and engineers to join our group. For clarity (because these terms vary by industry/company), scientists mainly focus on producing research results (e.g., papers and research software) while engineers mainly focus on software development and deliverables (e.g., system or application implementation). For scientist positions please expect to provide a CV with relevant publications.

The official application links are below, but please feel free to contact me directly if you have questions. (My HN username @slac.stanford.edu)

Scientist (Computer Science):

https://erp-hprdext.erp.slac.stanford.edu/psp/hprdext/EMPLOY...

Engineer (Computer Science):

https://erp-hprdext.erp.slac.stanford.edu/psp/hprdext/EMPLOY...

We've had some reports that the application site doesn't work well in Google Chrome. You might want to apply in Firefox.

There are some points in the middle, but it's rare. I worked on one of these [1]. We've been building the system for just over ten years, and are starting to see some truly killer apps being built on top of it [2, 3].

While it has some great benefits once you arrive, the upfront costs are enormous. You basically need to find a funding source (or sources) that will pay for this product while you're building it. Also, in order for the research payoff to be worth it, you need both the product itself, and subsequent innovations it enables, to be research-worthy. Not all areas of research can support this. On top of it all, even when you do this, you'll still spend years of effort in activities that are essentially not research. You're basically responsible for all of your own customer support, sales, marketing, etc.---like a startup, but without the financial upside if you succeed. Yes there is recognition and so on, but the payoffs aren't as dramatic. Most people aren't ready to commit to this path.

Keep in mind that you can't build this in 5 years either. So a single generation of PhD students can't get it done. The only reason we were successful is because the key staff on the project stuck around for 5+ years after their PhDs because we all believed in doing the work.

Given all that, I don't hold it against people at all who just want to build prototypes and then move on to the next thing. It's way less risky and higher reward relative to the costs.

[1]: https://legion.stanford.edu/

[2]: https://flexflow.ai/

[3]: https://developer.nvidia.com/cunumeric

I'm maintaining an internal change-data-capture application that uses a python library to decode mysql binlog and store the change records as json in the data lake (like Debezium). For our most busiest databases a single Cpython process couldn't process the amount of incoming changes in real time (thousands of events per second). It's not something that can be easily parallelized, as the bulk of the work is happening in the binlog decoding library (https://github.com/julien-duponchelle/python-mysql-replicati...).

So we've made it configurable to run some instances with Pypy - which was able to work through the data in realtime, i.e. without generating a lag in the data stream. The downside of using pypy was increased memory usage (4-8x) - which isn't really a problem. An actually problem that I didn't really track down was that the test suite (running pytest) was taking 2-3 times longer with Pypy than with CPython.

A few months ago I upgraded the system to run with CPython 3.11 and the performance improvements of 10-20% that come with that version now actually allowed us to drop Pypy and only run CPython. Which is more convenient and makes the deployment and configuration less complex.

doing the using Python, https://github.com/julien-duponchelle/python-mysql-replication, the recommended way of doing this

The BinLogStreamReader has several inputs that we need to retrieve. First we'll retrieve the cluster's secret with the database host/username/password and then we'll fetch the serverId we stored in S3.

From backend relational tables to data warehouses my team has mostly relied on change data capture replication. We use MySQL upstream, and historically used AWS DMS or Attunity Replicate to replicate directly to SQL server. Recently we made the switch to Snowflake, and used mostly AWS DMS to replicate CDC data to S3 (lists individual inserts, updates, deletes), and then from there use snowpipes to copy to snowflake and then a job to merge that data into the target table to get the latest state. In addition we've used this library in production https://github.com/noplay/python-mysql-replication, and still use it today for one high volume, critical data source. Generally we see data go end to end in a matter of minutes, but occasionally there are spikes in latency.