[
https://issues.apache.org/jira/browse/HDFS-7055?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=14154161#comment-14154161
]
Colin Patrick McCabe commented on HDFS-7055:
--------------------------------------------
bq. So, if no receiver set up, traces go nowhere?
Yeah.
bq. To see anything, you'd have to load a receiver with the just-added trace
command (i.e.HDFS-6956)?
There's two ways to turn on tracing:
* set {{hadoop.htrace.spanreceiver.classes}} (usually to
{{LocalFileSpanReceiver}} or {{ZipkinSpanReceiver}}
* use "hadoop trace \-add" to add tracing to an already-running daemon.
If you're testing, it's probably easier to just set up your Hadoop XML
configuration so that tracing will be running as soon as the daemon starts up.
This is also the only option for tracing a short-running program like the
FSShell. The dynamic changing is really more for production deployments, where
people might not want this on all the time, but don't want to restart daemons
to turn it on.
bq. If so, that seems cleaner. The alternative where files show up in /tmp if
no receiver is set is less so. Drop this facility from this patch?
Well, the files don't show up in /tmp unless {{LocalFileSpanReceiver}} is
configured. By default, there are no trace span receivers configured, and
nothing shows up in {{/tmp}}.
bq. On the patch, are these defined anywhere "NeverSampler"? Should we make it
so they are? Or should they be toString of the enums?
This is another thing I'd like to add to HTrace. I think HTrace should have
some method that creates a sampler based on a string which is the class name.
But right now that doesn't exist, so I had to add a hacked up version of it to
Hadoop (for now). We can easily take that out once HTrace has it, though.
I'd like to get the basic stuff in and then start shifting more things that we
think could be common code into HTrace.
> Add tracing to DFSInputStream
> -----------------------------
>
> Key: HDFS-7055
> URL: https://issues.apache.org/jira/browse/HDFS-7055
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: datanode, namenode
> Affects Versions: 2.6.0
> Reporter: Colin Patrick McCabe
> Assignee: Colin Patrick McCabe
> Attachments: HDFS-7055.002.patch, HDFS-7055.003.patch,
> HDFS-7055.004.patch, screenshot-get-1mb.png
>
>
> Add tracing to DFSInputStream.
--
This message was sent by Atlassian JIRA
(v6.3.4#6332)
