[jira] [Commented] (HTRACE-69) Filtering child spans by sampler

["Masatake Iwasaki (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/HTRACE-69?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14274848#comment-14274848 ] 

Masatake Iwasaki commented on HTRACE-69:
----------------------------------------

I think it is useful for the cases such as 
* filtering spans in routine which tend to be called many times (e.g. the span in o.a.h.hdfs.DFSInputStream#byteArrayRead).
* filtering spans based on package name or some keyword. (We need additional custom sampler too 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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