Prometheus returns HTTP 500 "seeker can't seek" error on /favicon.ico

[ricardbejarano]

What did you do?

1. Run Prometheus (I did docker run -it -p 9090:9090 quay.io/prometheus/prometheus:latest)
2. Go to http://localhost:9090/favicon.ico

What did you expect to see?

Prometheus' favicon.

What did you see instead? Under which circumstances?

A HTTP 500 response with Go's seeker can't seek error message.

System information

Darwin 21.4.0 x86_64

Prometheus version

prometheus, version 2.35.0 (branch: HEAD, revision: 6656cd29fe6ac92bab91ecec0fe162ef0f187654)
  build user:       root@cf6852b14d68
  build date:       20220421-09:53:42
  go version:       go1.18.1
  platform:         linux/amd64

Prometheus configuration file

No response

Alertmanager version

No response

Alertmanager configuration file

No response

Logs

None relevant to the issue (not even with --log.level=debug).

[fpapadamis]

This HTTP 500 on /favicon.ico seems to appear only when running Prometheus using docker. I have a 2.35.0 version running as a service and I get HTTP 200 and the actual image when I'm browsing /favicon.ico.

[mmuth]

Same issue here

[Nexucis]

the issue occurred also when using the PromQL editor. The UI cannot get the icon for the editor. There is a HTTP 500 Internal Server Error for http://localhost:9090/static/media/codicon.b3726f0165bf67ac6849.ttf.

And yes it's only in Docker. When we are using the binary directly, the issue doesn't happen.

[Nexucis]

issue wasn't there in 2.34. I'm looking about what changed between 2.34 and 2.35

[roidelapluie]

It's not only in docker, it's when building with promu crossbuild.

[Nexucis]

that's weird @roidelapluie. I downloaded the last archive and run the binary and I don't see the issue like @fpapadamis said it too.

[roidelapluie]

tar xvf prometheus-2.36.1.linux-amd64.tar.gz
cd prometheus-2.36.1.linux-amd64/
./prometheus 

then

curl 127.0.0.1:9090/favicon.ico
seeker can't seek

[Nexucis]

tar xvf prometheus-2.36.1.darwin-amd64.tar.gz
cd prometheus-2.36.1.darwin-amd64/
./prometheus

curl 127.0.0.1:9090/favicon.ico --output favicon.ico
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 15086  100 15086    0     0   983k      0 --:--:-- --:--:-- --:--:-- 4910k

no issue in darwin arch.

Perhaps the issue is more on linux actually

[roidelapluie]

My initial thinking: https://github.com/prometheus/common/blob/627089d3a7af73be778847aa577192b937b8d89a/server/static_file_server.go#L21

We need more extensions here. If the extension is not known, go http will seek the file to know the mimetype, which is not possible.

[roidelapluie]

prometheus/common#385

[roidelapluie]

After some testing, I confirm that prometheus/common#385 fixes the issue.

[Nexucis]

cool, thank you @roidelapluie. I commented the PR in order to add more mimeTypes support.

[roidelapluie]

#10879

[ricardbejarano]

Thank you, folks!

[DesireWithin]

Hello everyone, do you notice that alertmanager 0.24.0 have the same issue?