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https://issues.apache.org/jira/browse/HDFS-13607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16491357#comment-16491357
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Chao Sun commented on HDFS-13607:
---------------------------------
Thanks [~xkrogen]. The patch looks really good. I just have a few minor
comments:
# could we move {{readLock}} and {{writeLock}} before all the fields they
protect? this makes it easier to read.
# is {{initialTxnId}} necessary? seems it is only used in generating cache
miss exception.
# in {{retrieveEdits}}, in case the cache has two entries with different
layout version, it may add both to the outputBuffers, but the {{txnCount}} is
still set correctly. Not sure if this could be an issue.
# in some places we name transaction as {{tx}} (such as in {{startTx}}), while
in other places we use {{txn}} (such as in {{startTxnId}}). Maybe unify them?
# seems {{storeEdits}} will log an error when the cache is initialized and
{{highestTxnId = -1}}? because of:
{code}
if ((highestTxnId + 1) != startTx) {
// Cache is out of sync; clear to avoid storing noncontiguous regions
Journal.LOG.error(String.format("Edits cache is out of sync; " +
"looked for next txn id at %d but got start txn id for " +
"cache put request at %d", highestTxnId + 1, startTx));
}
{code}
# In {{getHeader}}:
{code}
} else if (exception.get() == null) {
throw new IOException("BUG/ERROR: Got null for header for version " +
layoutVersion + " but no exception found");
{code}
Could this ever happen? maybe an assertion is enough?
# {{getRawDataForTests}} is unused, but I suppose it will be in one of the
following patches?
> [Edit Tail Fast Path Pt 1] Enhance JournalNode with an in-memory cache of
> recent edit transactions
> --------------------------------------------------------------------------------------------------
>
> Key: HDFS-13607
> URL: https://issues.apache.org/jira/browse/HDFS-13607
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Components: ha, journal-node
> Reporter: Erik Krogen
> Assignee: Erik Krogen
> Priority: Major
> Attachments: HDFS-13607-HDFS-12943.000.patch,
> HDFS-13607-HDFS-12943.001.patch
>
>
> See HDFS-13150 for full design.
> This JIRA is to add the in-memory cache of recent edit transactions on the
> JournalNode. This JIRA does not include accesses to this cache.
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