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57 lines
1.9 KiB
Markdown
57 lines
1.9 KiB
Markdown
# Kernel Monitor
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*Kernel Monitor* is a problem daemon in node problem detector. It monitors kernel log
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and detects known kernel issues following predefined rules.
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The Kernel Monitor matches kernel issues according to a set of predefined rule list in
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[`config/kernel-monitor.json`](https://github.com/kubernetes/node-problem-detector/blob/master/config/kernel-monitor.json).
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The rule list is extensible.
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## Limitations
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* Kernel Monitor only supports file based kernel log now. It doesn't support log tools
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like journald. There is an [open issue](https://github.com/kubernetes/node-problem-detector/issues/14)
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to add journald support.
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* Kernel Monitor has assumption on kernel log format, now it only works on Ubuntu and
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Debian. However, it is easy to extend it to [support other log format](#support-other-log-format).
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## Add New NodeConditions
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To support new node conditions, you can extend the `conditions` field in
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`config/kernel-monitor.json` with new condition definition:
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```json
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{
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"type": "NodeConditionType",
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"reason": "CamelCaseDefaultNodeConditionReason",
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"message": "arbitrary default node condition message"
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}
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```
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## Detect New Problems
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To detect new problems, you can extend the `rules` field in `config/kernel-monitor.json`
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with new rule definition:
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```json
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{
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"type": "temporary/permanent",
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"condition": "NodeConditionOfPermanentIssue",
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"reason": "CamelCaseShortReason",
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"message": "regexp matching the issue in the kernel log"
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}
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```
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## Change Log Path
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Kernel log in different OS distros may locate in different path. The `log`
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field in `config/kernel-monitor.json` is the log path inside the container.
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You can always configure it to match your OS distro.
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## Support Other Log Format
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Kernel monitor uses [`Translator`](https://github.com/kubernetes/node-problem-detector/blob/master/pkg/kernelmonitor/translator/translator.go)
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plugin to translate kernel log the internal data structure. It is easy to
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implement a new translator for a new log format.
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