Switching between containers in the UI causes the container to crash.

[karami4yasser]

🔍 Check for existing issues

• Completed

How is Dozzle deployed?

Standalone Deployment

📦 Dozzle version

v8.13.14

✅ Command used to run Dozzle

panic: runtime error: slice bounds out of range [32:31]

goroutine 260 [running]:
github.com/amir20/dozzle/internal/docker.(*LogReader).Read(0xc000130e70)
        /dozzle/internal/docker/log_reader.go:62 +0xfd
github.com/amir20/dozzle/internal/container.(*EventGenerator).consumeReader(0xc0004cfaa0)
        /dozzle/internal/container/event_generator.go:85 +0x32
created by github.com/amir20/dozzle/internal/container.NewEventGenerator in goroutine 236
        /dozzle/internal/container/event_generator.go:46 +0x185

🐛 Describe the bug / provide steps to reproduce it

Switching between containers in the UI causes dozzle container to crash.

💻 Environment

oracle linux 8
podman version 4.9.4-rhel

📜 Dozzle logs are required for debugging purposes. You may need to enable debug mode. See https://dozzle.dev/guide/debugging.

{"level":"info","version":"v8.13.14","time":"2025-09-15T12:23:02Z","message":"Dozzle version v8.13.14"}
{"level":"info","version":"v8.13.14","clients":1,"time":"2025-09-15T12:23:03Z","message":"Connected to Docker"}
{"level":"info","version":"v8.13.14","time":"2025-09-15T12:23:03Z","message":"Accepting connections on :8080"}
panic: runtime error: slice bounds out of range [32:31]

goroutine 260 [running]:
github.com/amir20/dozzle/internal/docker.(*LogReader).Read(0xc000130e70)
        /dozzle/internal/docker/log_reader.go:62 +0xfd
github.com/amir20/dozzle/internal/container.(*EventGenerator).consumeReader(0xc0004cfaa0)
        /dozzle/internal/container/event_generator.go:85 +0x32
created by github.com/amir20/dozzle/internal/container.NewEventGenerator in goroutine 236
        /dozzle/internal/container/event_generator.go:46 +0x185

📸 If applicable, add screenshots to help explain your bug

[amir20]

I don't think this is related to switching between containers. I haven't seen any body else report this. Most likely it is related to something Podman is doing. The code:

message += tail[32:]  // I skip the first 32 chars because it is timestamp 

I am not sure how to fix this because I haven't actually seen it.

1. Are you sure it is when you switch containers? If you go directly to the container does it still do that?
2. Can you do export of the logs of the containers that is breaking this?

I could take a guess and try to fix it but I think something else is happening.

[karami4yasser]

Yes, this issue only happens when I start switching between containers (it usually fails on the second or third switch).

It starts working again only after restarting. Once it does, reaching dozzle/container/<id> does not cause it to crash.

Exporting logs also doesn’t seem to trigger the crash.

Please note that I have tested with & without :
DOZZLE_ENABLE_SHELL=true

[amir20]

Yes, this issue only happens when I start switching between containers (it usually fails on the second or third switch).

Hmm that is really weird.

Sorry I wasn't clear. Can you attach the logs? I can run it locally and see if something is happening.

🤔 I don't know what is causing this to be honest.

[amir20]

Also, not sure if you can help out, but test it on Docker? I am trying to narrow down if this is only happening on Podman or if it's something different with your cotnainers.

[ivoshm]

I've seen a similar bug in a similar environment (Podman), but unfortunately, I couldn't recreate the issue. It's probably related to the content of the log.

It would definitely help to verify that there are at least 32 characters in the tail variable before skipping it. Then, we would not get a panic, and we could see in Dozzle what Podman is actually sending.

[amir20]

Thanks @ivoshm . That helps to narrow. I'll have to setup podman on a linux vm and test it out.

It would definitely help to verify that there are at least 32 characters in the tail variable before skipping it. Then, we would not get a panic, and we could see in Dozzle what Podman is actually sending.

It's a little more complicated than that. Because that code should only happen for extremely large logs. That's why I need to reproduce to understand what is going on.

[amir20]

@ivoshm @karami4yasser I created a new Ubuntu VM and installed podman version 5.4.1. I did

podman run --volume /run/user/501/podman/podman.sock:/var/run/docker.sock -d -p 8080:8080 docker.io/amir20/dozzle:latest

Then did a bunch of fake containers. I switched around for 20+ times and nothing broke.

I would need to see the content of logs to help or somehow reproduce it.