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https://issues.apache.org/jira/browse/HDFS-7189?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14279238#comment-14279238
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Colin Patrick McCabe commented on HDFS-7189:
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bq. But I think the spans \[for queryDatanodeForHdfsBlocksMetadata comments\]
should be in the same trace tree and as a child span instead of start a new
trace. So we should pass the trace info (trace id parent span id) to continue
span.
Good idea. That way, if a {{DFSClient#getBlockStorageLocations}} call takes a
long time, the trace might be helpful to show which datanode is lagging.
bq. Some DFSClient operations don't have trace spans, should we add them?
The operations that I didn't add tracing for broke down into two categories:
* Things that we're going to do later in the "add tracing to DFSOutputStream"
change (this is why callAppend isn't traced, append, connectToDN, etc.)
* Things that look like they're not very time-consuming. Like
getCryptoProtocolVersion which just fetches the version out of a
FileEncryptionInfo object.
Actually, though, I do see one or two things where I should add tracing, like
getStoragePolicies. Let me add those.
We can always add tracing to stuff later, so I don't think this should be a
blocker for this going in. And we will certainly adjust the trace points later
based on what we learn... to put more in some places and fewer in others. But
thanks for getting me thinking about this.
bq. Typo? It should be "dst"
Argh. Thanks
bq. In getSrcDstTraceScope, we'd better check dst != null too.
yeah
> Add trace spans for DFSClient metadata operations
> -------------------------------------------------
>
> Key: HDFS-7189
> URL: https://issues.apache.org/jira/browse/HDFS-7189
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, namenode
> Affects Versions: 2.7.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-7189.001.patch, HDFS-7189.003.patch,
> HDFS-7189.004.patch, HDFS-7189.005.patch, HDFS-7189.006.patch
>
>
> We should add trace spans for DFSClient metadata operations. For example,
> {{DFSClient#rename}} should have a trace span, etc. etc.
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