How to collect the span that only exsits in a slow trace

[jackiepon31]

BackGround：
In order to reduce the pression from es storage side and build a swify way to trouble shoot slow transaction.
I wanna find a way to collect the trace and its spans when the whole distributed trace time cost is above a certain value.
But the spans-collector own by the client-side cannot decide to collect the span or not when the whole trace is not end.

[wu-sheng]

I don't know what do you mean exactly, and what is spans-collector. There are not SkyWalking concept, and no span-oriented sampling mechanism even. Even, we keep segment in the storage, rather than separate span. So, can't follow your question.

[jackiepon31]

Thanks for your reply，
Oh，sorry , I will try to re-explain my point .
Can Skywalking keep the trace segment in storage only when the whole tracing time cost is above a certain value.
And why i need this, plz refer to the backgroud i 've offerd above

[wu-sheng]

For whole trace, no. This kind of thing could cause distributed global lock and time windows, which is really a bad idea for high performance system monitoring. We have tested and abandoned it back to 2015.
You could sample the slow segments of a trace, but it would not guarantee you could get the whole complete trace, because the fast segments will be ignored too.

[jackiepon31]

Ya , I got your point. It's really tough right now , cause i did put myself in a contradictory place....
If I try to sample the segments , the slow trace will occur even more uncommonly and I cannot troubleshoot the throttle of my systems under discomple trace.
If I wanna catch and storage the slow trace dataset only, i need a time-window based top-processing service, but surly we'll face the throttle from this service and we cannot explore the trace with high perfomance.

[wu-sheng]

Correct, this is the case.