Trace Profiting configuration

[137-zwq]

environment:skywalking10.1.0、java-agent9.3.0、elasticsearch7.10.2

I have found that there is currently an issue with Trace Profiling where the APIs collected in the trace are in compliance with the configuration in the task, but not all of them have been collected. Is there a problem with Trace Profiling in this situation, or is it designed in this way.
After creating the performance analysis task, the task configuration information is as follows:

1. Configure Dump Period
   When setting the dump period for the task configuration to 10ms, according to the documentation, APIs with a duration greater than 10ms should be able to be collected by the task. However, it was found that not all interface data in the trace was collected, with a total of 4 interfaces. After the task was completed, the API interface with a response time of 15ms did not appear in the sampling trace of the task. As shown in the following figure.
   
   
   

2. Configure Min Duration Threshold
   When setting the Min Duration Threshold to 100ms. API interfaces with response times of 105ms, 106ms, etc. that meet the task configuration were not collected until API response times of 120ms or larger were detected by the task's sampling tracking.
   
   
   

[wu-sheng]

Sampling is the base of the profiling, from call stack to the matched calls.
There is no guarantee.

[137-zwq]

The meaning is that the API interface in the link does not guarantee that the profiling task will be sampled. Are the above scenarios all normal phenomena?

[wu-sheng]

Yes. And the edge case, such as you set threshold to 100ms, and request is around 100-110ms, sometimes, it got sampled only.

This is used for slow and high-frequence things, not catch all methods all the times.

There are plenty of debug tools are good at that, you don't need an APM to do that. In APM, we just address slow requests and some unnormal cases in product env. So, impact matters. Impact low for target service and impact huge enough of the performance issue.