[
https://issues.apache.org/jira/browse/HDFS-15160?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=17118535#comment-17118535
]
Stephen O'Donnell commented on HDFS-15160:
------------------------------------------
Hi [~Jiang Xin] - it would be a great help if you could try this on your
production cluster. From review we feel the 005 patch is good, but real world
testing would give us more confidence.
{quote}
But the code `synchronized(replica) ... ` in method getBlockLocalPathInfo
confuse me. It's holding the write lock, doesn't need to worry about updating
genStamps . I assume that you wanted to change method getBlockLocalPathInfo in
read lock, am I right?
{quote}
Well spotted - you are correct. I have uploaded a 006 patch to make the lock in
getBlockLocalPathInfo a readlock.
> ReplicaMap, Disk Balancer, Directory Scanner and various FsDatasetImpl
> methods should use datanode readlock
> -----------------------------------------------------------------------------------------------------------
>
> Key: HDFS-15160
> URL: https://issues.apache.org/jira/browse/HDFS-15160
> Project: Hadoop HDFS
> Issue Type: Improvement
> Components: datanode
> Affects Versions: 3.3.0
> Reporter: Stephen O'Donnell
> Assignee: Stephen O'Donnell
> Priority: Major
> Attachments: HDFS-15160.001.patch, HDFS-15160.002.patch,
> HDFS-15160.003.patch, HDFS-15160.004.patch, HDFS-15160.005.patch,
> image-2020-04-10-17-18-08-128.png, image-2020-04-10-17-18-55-938.png
>
>
> Now we have HDFS-15150, we can start to move some DN operations to use the
> read lock rather than the write lock to improve concurrence. The first step
> is to make the changes to ReplicaMap, as many other methods make calls to it.
> This Jira switches read operations against the volume map to use the readLock
> rather than the write lock.
> Additionally, some methods make a call to replicaMap.replicas() (eg
> getBlockReports, getFinalizedBlocks, deepCopyReplica) and only use the result
> in a read only fashion, so they can also be switched to using a readLock.
> Next is the directory scanner and disk balancer, which only require a read
> lock.
> Finally (for this Jira) are various "low hanging fruit" items in BlockSender
> and fsdatasetImpl where is it fairly obvious they only need a read lock.
> For now, I have avoided changing anything which looks too risky, as I think
> its better to do any larger refactoring or risky changes each in their own
> Jira.
--
This message was sent by Atlassian Jira
(v8.3.4#803005)
---------------------------------------------------------------------
To unsubscribe, e-mail: hdfs-issues-unsubscr...@hadoop.apache.org
For additional commands, e-mail: hdfs-issues-h...@hadoop.apache.org
