Add a LongTaskTimer for every Observation in TimerObservationHandler #3215
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This way handlers will be able to handle tasks that can potentially take long differently (e.g.: tracking active tasks while they are active)
jonatan-ivanov
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...er-core/src/main/java/io/micrometer/core/instrument/observation/TimerObservationHandler.java
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...crometer-samples-core/src/main/java/io/micrometer/core/samples/ObservationHandlerSample.java
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jonatan-ivanov
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I like this. I think it's worthwhile in most cases to have a LTT along with a Timer to see metrics on in-flight tasks. In theory, if something being timed has a timeout that's less than the step interval - meaning an active task would never be timed across two step intervals, then I guess the LTT becomes less interesting. As long as the overhead of the LTT isn't a problem, though, I think it is fine.
The difference in tags is a potential point of confusion. We should document it in the JavaDoc perhaps.
shakuzen
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module: micrometer-core
| .lowCardinalityKeyValue("staticTag", "42").start(); | ||
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| // created after start, LongTaskTimer won't have it | ||
| observation.lowCardinalityKeyValue("dynamicTag", "24"); |
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In general that shouldn't really happen. We will recommend to the users that they create a non started observation, and always use a key value provider (I think that in extremely rare cases they could set key value pairs manually)
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The KeyValueProvider is the same case since it is queried at stop when you have all the details in the context and the LongTaskTimer is created at start.
shakuzen
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This PR changes the behavior of
TimerObservationHandlerso that it will always create an additionalLongTaskTimer(on top of theTimer) so that the active task can be observed too on-the-fly.There is a caveat/issue with this: since the
KeyValuesProvideris used atstop, none of those tags will be added to theLongTaskTimer. Also, the tags that are added to theObservationafterstartwon't be added to theLongTaskTimer./cc @cppwfs