Comment by jeffbee
I wouldn't. "Trace contains an error" is a hideously bad criterion for sampling. If you have some storage subsystem where you always hedge/race reads to two replicas then cancel the request of the losing replica, then all of your traces will contain an error. It is a genuinely terrible feature.
Local logging of error conditions is the way to go. And I mean local, not to a central, indexed log search engine; that's also way too expensive.
I disagree that it's a bad criterion. The case you describe is what sounds difficult, treating one error as part of normal operations and another as not. That should be considered its own kind of error or other form of response, and sampling decisions could take that into consideration (or not).