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https://issues.apache.org/jira/browse/HTRACE-69?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14386195#comment-14386195
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Colin Patrick McCabe commented on HTRACE-69:
--------------------------------------------
If {{DFSInputStream#byteArrayRead}} is being too chatty, another option is to
get rid of that trace span (and the ones on the {{BlockReader#read}} methods).
We could just trace the functions which refill the buffers inside the
{{BlockReader}} objects. That is the main operation that is time-consuming, so
it might be more appropriate to do that anyway. I guess I need to look at a
few more trace examples to get a feeling for this.
> Filtering child spans by sampler
> --------------------------------
>
> Key: HTRACE-69
> URL: https://issues.apache.org/jira/browse/HTRACE-69
> Project: HTrace
> Issue Type: New Feature
> Reporter: Masatake Iwasaki
> Assignee: Masatake Iwasaki
>
> Trace#startSpan respect the sampler given as argument only when there is no
> ongoing span (i.e. when creating new root span).
> {code}
> public static TraceScope startSpan(String description, Sampler<TraceInfo>
> s, TraceInfo tinfo) {
> Span span = null;
> if (isTracing() || s.next(tinfo)) {
> {code}
> Adding API starting span if {{(isTracing() && s.next(tinfo))}} enables
> filtering of child spans.
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