zlacker

>>>> 2. Postgres preserves your data if it goes down

>>>Not if you're using a SKIP LOCKED queue,

Can you provide a reference for this? I'm not aware that using SKIP LOCKED data is treated any differently to other Postgres data in terms of durability.

>>andrew+(OP)
It's exactly the same case as SQS in that if your disk interface dies in mid write of a message you lose it the same as if your interface to SQS or SQS itself dies mid-write, you lose it.

The rest of the sentence is a challenge, "show me a data loss bug in SQS that extends beyond the failure cases you've already implicitly agreed to using postgres itself."

>>KirinD+j
What possibilities are there for a write to fail that the database server cannot react to? I am under the impression that a write error like this would be reported as a failure to run the statement and the application is responsible for handling that.

>>gmueck+sc
The box turning off, the disk interface failing, and/or the link to the database failing in mid instruction.

Same as SQS.

>>KirinD+Pi
All of those would result in a write failure from the application's perspective, which is fine, and must be accounted for regardless (e.g. retry, two phase commit, log an error, whatever).

>>KirinD+Pi
Also the FS might report the data as written but its actually in a write cache and will be lost if the plug is pulled.

>>KirinD+Pi
But you have to explicitly delete the message from SQS, right? You'd only delete after confirming you processed the message, right? So if you die mid-instruction in processing a message, the message just re-appears in the SQS queue after the visibility timeout.

>>z3t4+Py
Not an issue if you follow th e recommendations in the PostgeSQL documentation. The way to comfigure write caches is described there.

>>KirinD+j
SKIP LOCKED is a read-side feature. PG is a problem for u/andrewstuart because they have to manage it themselves (unless they're getting a PG service from a cloudy provider, say) and that's harder than it is for Amazon to manage SQS.

>>mcquee+CD
That's a feature, and one your have to replicate in your postgres queue.