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https://issues.apache.org/jira/browse/HDFS-13609?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16520115#comment-16520115
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Yiqun Lin commented on HDFS-13609:
----------------------------------
Hi [~xkrogen], recently I am learning *Consistent Reads from Standby Node*.
Just reviewed on this, two comments:
* Looks like we should do a Precondition check when getting {{maxTxnsPerRpc}}
value from configuration. If a invalid max -txns value configured (0 or <0), no
edits data will be returned.
*
{code:java}
private void selectRpcInputStreams(Collection<EditLogInputStream> streams,
long fromTxnId, boolean onlyDurableTxns) throws IOException {
...
int highestTxnCount = responseCounts.get(responseCounts.size() - 1);
if (LOG.isDebugEnabled() || highestTxnCount < 0) {
...
msg.append(">");
if (highestTxnCount < 0) {
throw new IOException("Did not get any valid JournaledEdits " +
"responses: " + msg);
} else {
LOG.debug(msg.toString());
}
}
...
}
{code}
Here {{highestTxnCount < 0}} is accurate? Seems {{highestTxnCount <= 0}} is
right. The txnCount can be 0 returned by {{JournaledEditsCache#retrieveEdits}}
(For example, when requestedStartTxn > highestTxnId).
> [Edit Tail Fast Path Pt 3] NameNode-side changes to support tailing edits via
> RPC
> ---------------------------------------------------------------------------------
>
> Key: HDFS-13609
> URL: https://issues.apache.org/jira/browse/HDFS-13609
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha, namenode
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Priority: Major
> Attachments: HDFS-13609-HDFS-12943.000.patch,
> HDFS-13609-HDFS-12943.001.patch, HDFS-13609-HDFS-12943.002.patch
>
>
> See HDFS-13150 for the full design.
> This JIRA is targetted at the NameNode-side changes to enable tailing
> in-progress edits via the RPC mechanism added in HDFS-13608. Most changes are
> in the QuorumJournalManager.
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