[
https://issues.apache.org/jira/browse/HDFS-13607?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16505553#comment-16505553
]
Erik Krogen commented on HDFS-13607:
------------------------------------
I had some offline discussion with [~shv] about whether or not it was really
necessary for the cache to support multiple layout versions. Given that the
layout version only changes, at most, on major/minor version upgrades, it is an
extremely infrequent event. We can simplify the cache, reducing the need for
two of the maps, by only storing a single layout version in the cache at any
given time. When a new layout version is encountered, we simply clear the old
entries out of the cache. The Standby NameNodes will get a CacheMissException
upon attempting to read older edits, and will simply fall back to the streaming
mechanism for one iteration before catching up and resuming with the new layout
version. We feel this is a reasonable tradeoff of performance vs. code
complexity, but welcome thoughts from others.
These changes incorporated in v005 patch.
> [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, HDFS-13607-HDFS-12943.002.patch,
> HDFS-13607-HDFS-12943.003.patch, HDFS-13607-HDFS-12943.004.patch,
> HDFS-13607-HDFS-12943.005.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.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
