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From "Masatake Iwasaki (JIRA)" <j...@apache.org>
Subject [jira] [Commented] (HDFS-11622) TraceId hardcoded to 0 in DataStreamer, correlation between multiple spans is lost
Date Fri, 07 Apr 2017 00:48:42 GMT

    [ https://issues.apache.org/jira/browse/HDFS-11622?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15960078#comment-15960078
] 

Masatake Iwasaki commented on HDFS-11622:
-----------------------------------------

bq. The DFSPacket initializes the parents field when it is dumping the data in dataQueue with
the line packet.addTraceParent(Tracer.getCurrentSpanId()), thus getting current trace from
the ThreadLocal. At this point, I feel that we can also get the value of trace ID and add
the info inside the DFSPacket. Any thoughts on this one?

As you pointed out, the current {{dataStreamer}} span in branch-2.7 seems not to have situation
setting multiple parents. It looks like extention for future use?


> TraceId hardcoded to 0 in DataStreamer, correlation between multiple spans is lost
> ----------------------------------------------------------------------------------
>
>                 Key: HDFS-11622
>                 URL: https://issues.apache.org/jira/browse/HDFS-11622
>             Project: Hadoop HDFS
>          Issue Type: Bug
>          Components: tracing
>            Reporter: Karan Mehta
>
> In the {{run()}} method of {{DataStreamer}} class, the following code is written. {{parents\[0\]}}
refer to the {{spanId}} of the parent span.
> {code}
>               one = dataQueue.getFirst(); // regular data packet
>               long parents[] = one.getTraceParents();
>               if (parents.length > 0) {
>                      scope = Trace.startSpan("dataStreamer", new TraceInfo(0, parents[0]));
>                 // TODO: use setParents API once it's available from HTrace 3.2
>                 // scope = Trace.startSpan("dataStreamer", Sampler.ALWAYS);
>                 // scope.getSpan().setParents(parents);
>               }
> {code}
> The {{scope}} starts a new TraceSpan with a traceId hardcoded to 0. Ideally it should
be taken when {{currentPacket.addTraceParent(Trace.currentSpan())}} is invoked. This JIRA
is to propose an additional long field inside the {{DFSPacket}} class which holds the parent
{{traceId}}. 



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