Jepsen: NATS 2.12.1
by aphyr on 12/8/2025, 6:51:03 PM
https://jepsen.io/analyses/nats-2.12.1
Comments
by: vrnvu
Sort of related. Jepsen and Antithesis recently released a glossary of common terms which is a fantastic reference.<p><a href="https://jepsen.io/blog/2025-10-20-distsys-glossary" rel="nofollow">https://jepsen.io/blog/2025-10-20-distsys-glossary</a>
12/8/2025, 7:23:12 PM
by: merb
> 3.4 Lazy fsync by Default<p>Why? Why do some databases do that? To have better performance in benchmarks? It’s not like that it’s ok to do that if you have a better default or at least write a lot about it. But especially when you run stuff in a small cluster you get bitten by stuff like that.
12/8/2025, 7:34:47 PM
by: rdtsc
> By default, NATS only flushes data to disk every two minutes, but acknowledges operations immediately. This approach can lead to the loss of committed writes when several nodes experience a power failure, kernel crash, or hardware fault concurrently—or in rapid succession (#7564).<p>I am getting strong early MongoDB vibes. "Look how fast it is, it's web-scale!". Well, if you don't fsync, you'll go fast, but you'll go even faster piping customer data to /dev/null, too.<p>Coordinated failures shouldn't be a novelty or a surprise any longer these days.<p>I wouldn't trust a product that doesn't default to safest options. It's fine to provide relaxed modes of consistency and durability but just don't make them default. Let the user configure those themselves.
12/8/2025, 8:16:10 PM
by: clemlesne
NATS is a fantastic piece of software. But doc’s unpractical and half backed. That’s a shame to be required to retro engineer the software from GitHub to know the auth schemes.
12/8/2025, 7:41:26 PM
by: maxmcd
> > You can force an fsync after each messsage [sic] with always, this will slow down the throughput to a few hundred msg/s.<p>Is the performance warning in the NATS possible to improve on? Couldn't you still run fsync on an interval and queue up a certain number of writes to be flushed at once? I could imagine latency suffering, but batches throughput could be preserved to some extent?
12/8/2025, 8:20:30 PM
by: gostsamo
Thanks, those reports are always a quiet pleasure to read even if one is a bit far from the domain.
12/8/2025, 7:57:57 PM
by: selectodude
[flagged]
12/8/2025, 7:12:39 PM