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https://issues.apache.org/jira/browse/HDFS-8213?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14507888#comment-14507888
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Colin Patrick McCabe commented on HDFS-8213:
--------------------------------------------
bq. I think Billie Rinaldi is correct here; the client should not instantiate
it's own SpanReceiverHost, but instead depend on the process in which it
resides to provide. This is how HBase client works as well.
[~ndimiduk], what if I want to trace an HBase PUT all the way through the
system? You're saying that the HBase client can't activate tracing on its own,
so I have to make code changes to the process doing the PUT (i.e. the user of
the HBase client) in order to get that info? Seems like a limitation.
It's also worth pointing out that adding a {{SpanReceiverHost}} to the
{{DFSClient}} is not really a new change... it goes back to HDFS-7055, last
October. So it's been in there at least 6 months. Of course we can revisit it
if that makes sense, but it's not really "new" except in the sense that it took
a very long time to do another Hadoop release with that in it. (We really
should start being better with releases...)
Thinking about this a little more, another possible resolution here is to
change the configuration keys which the DFSClient looks for so that it's
different than the ones which the NameNode and DataNode look for. Right now
{{hadoop.htrace.spanreceiver.classes}} will activate span receivers in both the
NN and the DFSClient. But the DFSClient could instead look for
{{hdfs.client.htrace.spanreceiver.classes}}. Then [~billie.rinaldi] could use
the same configuration file for everything, and the dfsclient would never
create its own span receivers or samplers. And I could continue to trace the
dfsclient without modifying daemon code. Seems like a good resolution.
> DFSClient should not instantiate SpanReceiverHost
> -------------------------------------------------
>
> Key: HDFS-8213
> URL: https://issues.apache.org/jira/browse/HDFS-8213
> Project: Hadoop HDFS
> Issue Type: Bug
> Affects Versions: 2.7.0
> Reporter: Billie Rinaldi
> Assignee: Brahma Reddy Battula
> Priority: Critical
>
> DFSClient initializing SpanReceivers is a problem for Accumulo, which manages
> SpanReceivers through its own configuration. This results in the same
> receivers being registered multiple times and spans being delivered more than
> once. The documentation says SpanReceiverHost.getInstance should be issued
> once per process, so there is no expectation that DFSClient should do this.
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