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https://issues.apache.org/jira/browse/HDFS-10519?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15330013#comment-15330013
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Jiayi Zhou commented on HDFS-10519:
-----------------------------------

Maybe I got something wrong, but isn't the MetaRecoveryContext already null at 
the beginning?

In doTailEdits() from EditLogTailer, we have 
                              streams = editLog.selectInputStreams(lastTxnId + 
1, 0, null, inProgressTail);

Here, MetaRecoverContext is null. And in image.LoadEdits(), we have
                              public long 
loadEdits(Iterable<EditLogInputStream> editStreams,
                                      FSNamesystem target) throws IOException {
                                return loadEdits(editStreams, target, null, 
null);
                              }
MetaRecoveryContext is also null.

Also, I don't know why toAtLeastTxId is always set to 0 in the implementation, 
making the checkForGaps() method no use. If we set it to some other value, like 
lastTxnId + 1, the multiple replay should be rejected.

> Add a configuration option to enable in-progress edit log tailing
> -----------------------------------------------------------------
>
>                 Key: HDFS-10519
>                 URL: https://issues.apache.org/jira/browse/HDFS-10519
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>          Components: ha
>            Reporter: Jiayi Zhou
>            Assignee: Jiayi Zhou
>            Priority: Minor
>         Attachments: HDFS-10519.001.patch, HDFS-10519.002.patch
>
>
> Standby Namenode has the option to do in-progress edit log tailing to improve 
> the data freshness. In-progress tailing is already implemented, but it's not 
> enabled as default configuration. And there's no related configuration key to 
> turn it on.
> Adding a related configuration key to let Standby Namenode is reasonable and 
> would be a basis for further improvement on Standby Namenode.



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