Buffer limit API for message events, links, and annotations?

[jgracenin]

I have a Go service with a long running stream that had a memory leak due to unbounded storage of
message events. This was a known limitation: census-instrumentation/opencensus-go#401

gRPC's MAX_CONNECTION_AGE would help, but I also made a quick fork with a limit on message events, annotations, and links: census-instrumentation/opencensus-go#824 .

Do any other language implementations already limit these internal structures yet (events, links annotations) yet?

The PR also sparked a larger discussion on more granular limits for some future features (e.g. classified events, links annotations), but that's a larger API change and is probably better to be discussed here.

[rakyll]

/cc @sebright @g-easy @songy23

[songy23]

Do any other language implementations already limit these internal structures yet (events, links annotations) yet?

Yes, in Java we have some default limit for them:

  private static final int DEFAULT_SPAN_MAX_NUM_ATTRIBUTES = 32;
  private static final int DEFAULT_SPAN_MAX_NUM_ANNOTATIONS = 32;
  private static final int DEFAULT_SPAN_MAX_NUM_MESSAGE_EVENTS = 128;
  private static final int DEFAULT_SPAN_MAX_NUM_LINKS = 128;

Users can override these numbers with TraceConfig.updateActiveTraceParams.

[rakyll]

@songy23, can we update https://github.com/census-instrumentation/opencensus-specs/blob/master/trace/TraceConfig.md to represent this? So, other languages can refer to the spec when implementing.

[songy23]

Sure, working on a PR now.

[g-easy]

#138 (comment) FYI C++ has the same.

[bogdandrutu]

I think the specs has limits now. This needs to be implemented in Go and other languages now.