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docs: Describe how the containerdebug logs are collected #975

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35 changes: 30 additions & 5 deletions modules/concepts/pages/observability/containerdebug.adoc
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Expand Up @@ -4,7 +4,7 @@
All Stackable-managed products regularly log information about their operating
environment, such as available disk interfaces and network interfaces.

This logging is performed by our https://github.com/stackabletech/containerdebug[containerdebug{external-link-icon}^] tool.
This logging is performed by our https://github.com/stackabletech/operator-rs/tree/main/crates/containerdebug[containerdebug{external-link-icon}^] tool.

NOTE: This tool is intended as a debugging aid, and the particular information or
format should not be considered stable.
Expand All @@ -17,9 +17,34 @@ main product container.

== Output

The collected information is logged to the Kubernetes pod logs (readable via `kubectl logs <pod>`)
and to the xref:observability/logging.adoc#architecture[shared Stackable log dir]
(for pickup by the Vector log agent).
containerdebug writes its output to three places: the pod logs, a rotating log file for the log aggregation, and a state file with the result of the latest run.

@NickLarsenNZ NickLarsenNZ Nov 4, 2026

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I assume this means STDOUT/STDERR. maybe we could say console logs. Unless Pod logs has been used in other places to mean the same thing.

@NickLarsenNZ NickLarsenNZ Nov 4, 2026

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I assume...

I see it clarified below. Maybe its fine. Leaving the comment in case you have an opinion.


Additionally, it is written as JSON to `/stackable/log/containerdebug-state.json`.
=== Pod logs

The collected information is logged to the Kubernetes pod logs, readable via `kubectl logs <pod>`.

=== Aggregated log files

The information is also written to the xref:observability/logging.adoc#architecture[shared Stackable log dir], so that the Vector log agent collects it and forwards it to the Vector aggregator.
The operators enable these file logs by setting the environment variable `FILE_LOG_DIRECTORY` to `/stackable/log/containerdebug` in the product container.
They configure the rotation with `FILE_LOG_ROTATION_PERIOD` set to `hourly`, because rotation is off by default, and with `FILE_LOG_MAX_FILES` set to `2`, so that the files do not fill up the log volume, whose size is capped.
The resulting files are named `containerdebug.<date>.tracing-rs.json`.

In the aggregated logs, these events carry the container name `containerdebug`.
No Kubernetes container of that name exists, because containerdebug runs in the background of the product container.
The name is derived by the Vector agent from the directory which the files lie in.

[CAUTION]
====
If you override `FILE_LOG_DIRECTORY`, then the directory has to stay exactly one level below `/stackable/log`, because the Vector agent takes the container name from that path segment.
A directory next to it, such as `/stackable/log/<product>`, mixes the containerdebug events into the logs of that container.

@NickLarsenNZ NickLarsenNZ Nov 4, 2026

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I think this is a little hard to understand. I'm guessing it means if the user were to set FILE_LOG_DIR to the product directory, then the containerdebug logs would be mixed with the product logs.

Any other path stops the collection of these files, and a path outside `/stackable/log` additionally leaves the volume whose size is capped.
====

The log level of these files is independent of the log configuration of the product container.
It defaults to `INFO` and can be changed with the environment variable `FILE_LOG_LEVEL`.

=== State file

The collected information is additionally written as JSON to `/stackable/log/containerdebug-state.json`.

@NickLarsenNZ NickLarsenNZ Nov 4, 2026

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I assume this doesn't get scraped by vector.

This file only contains the output from the _latest_ containerdebug run.
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