(502) Unknown error?

Getting Help
1

Hello,

On my macOS Tahoe 26.6 system, I run a restic backup script every morning at 0707 through launchd. It runs a backup to Backblaze B2 using the S3 backend; if that succeeds, it runs a forget with prune; if that succeeds, it runs a check with --read-data-subset. All has been running well for several weeks.

This morning, I found the following output:

using parent snapshot d93fa77f

Files:           5 new,    17 changed, 19978 unmodified
Dirs:            2 new,  1284 changed,     0 unmodified
Added to the repository: 940.865 MiB (845.401 MiB stored)

processed 20000 files, 427.247 GiB in 0:18
snapshot 668bb186 saved
[ERROR] 2026/07/28 07:07:24 (502) Unknown: An unknown error occurred.

Since a snapshot was saved, I guess the error occurred at the beginning of the forget phase?

I ran the job manually when I saw the error (about 90 minutes later) and it was fine, with no errors.

Okay, so it’s not reasonable for me to ask “what happened” because the error message is pretty clear. But I’m wondering if there is anything I should follow up? Or if things keep running with no errors, do I just assume I’m good?

Thank you.

restic 0.19.1 compiled with go1.26.5 on darwin/arm64
2

I did a bit of research and discovered this is an HTTP error code. So, I assume it was somehow generated by the S3 backend due to connection errors with Backblaze.

I am closing the help request, it is unlikely to be a restic issue.

3

Yes, your assessment is correct – restic has spoken with a backend over HTTP and that backend reported a 5xx error status code. I’m guessing it was just an intermittent error on their side, nothing to sweat about.

Maybe you should add output to your script such that it tells you what it’s doing, e.g. when it starts a new step.