[QUESTION] Possibility to use duration as policy for tail-based sampling

[tsologub]

Does Otel collector provide a possibility to use duration as a policy?
I am trying to achieve that with the following collector configuration:

...
processors:
  batch:
  queued_retry:
  tail_sampling:
    decision_wait: 10s
    policies:
      - name: sample-long-running-requests
        type: numeric_attribute
        numeric_attribute: {key: duration, min_value: 1000, max_value: 10000}
...

[pjanotti]

Hi @tsologub, the internal format carry duration as fields of the span, not as an attribute. So it won't work, you need a sampling policy to handle that. Would you be interested in writing one? I can give you some pointers.

[pjanotti]

Alternatively, if you control the instrumentation you can add an attribute named duration to work as you intended.

[tsologub]

Would you be interested in writing one?

sure. I'd be glad to. Give me some pointers, examples where can I start?

[pjanotti]

You need to implement a policy evaluator (see example here). This is an object with a simple interface: the method Evaluate that tells if a trace should be sampled or not. Your criteria for Evaluate should check the difference between EndTime and StartTime for each span to see if it satisfies the criteria configured for the evaluator.

[jpkrohling]

This has been recently implemented with the latency policy (#3750).