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Add documentation details about plugin logging

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Joshua Boniface 2023-02-23 22:24:07 -05:00
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docs/manuals/health-plugins.md
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@ -153,6 +153,22 @@ An instance of the `PluginResult` object is helpfully created by the caller and
Finally, the `PluginResult` instance stored as `self.plugin_result` must be returned by the run function to the caller upon completion so that it can be added to the node state. Finally, the `PluginResult` instance stored as `self.plugin_result` must be returned by the run function to the caller upon completion so that it can be added to the node state.
### Logging
The MonitoringPlugin class provides a helper logging method (usable as `self.log()`) to assist a plugin author in logging messages to the node daemon console log. This function takes one primary argument, a string message, and an optional `state` keyword argument for alternate states.
The default state is `d` for debug, e.g. `state="d"`. The possible states for log messages are:
* `"d"`: Debug, only printed when the administrator has debug logging enabled. Useful for detailed analysis of the plugin run state.
* `"i"`: Informational, printed at all times but with no intrinsic severity. Use these very sparingly if at all.
* `"t"`: Tick, matches the output of the keepalive itself. Use these very sparingly if at all.
* `"w"`: Warning, prints a warning message. Use these for non-fatal error conditions within the plugin.
* `"e"`: Error, prints an error message. Use these for fatal error conditions within the plugin.
None of the example plugins make use of the logging interface, but it is available for custom plugins should it be required.
The final output message of each plugin is automatically logged to the node daemon console log with `"t"` state at the completion of all plugins, if the `log_keepalive_plugin_details` configuration option is true. Otherwise, no final output is displayed. This setting does not affect messages printed from within a plugin.
### Example Health Plugin ### Example Health Plugin
This is a terse example of the `load` plugin, which is an extremely simple example that shows all the above requirements clearly. Comments are omitted here for simplicity, but these can be seen in the actual plugin file (at `/usr/share/pvc/plugins/load` on any node). This is a terse example of the `load` plugin, which is an extremely simple example that shows all the above requirements clearly. Comments are omitted here for simplicity, but these can be seen in the actual plugin file (at `/usr/share/pvc/plugins/load` on any node).