[
https://issues.apache.org/jira/browse/HDFS-13688?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16529284#comment-16529284
]
Chen Liang commented on HDFS-13688:
-----------------------------------
There have been some offline discussion on msync, sharing some notes here for
reference.
1. it is preferred not to have AlignmentContext in DFSClient. The current
reason AlignmentContext in DFSClient as in WIP patch is that for a fresh client
who has no initial state id, the client needs to check AlignmentContext, to see
if state id is set, if not, DFSClient makes a RPC call to ANN. Since DFSClient
has to make this check, it needs to see the AlignmentContext instance. If there
is an alternative way where DFSClient does not need to explicitly make this
check, there is no need to have AlignmentContext in DFSClient. Still need to
investigate if there is an alternative way though.
2. it is preferred not to check method name for msync
3. need to make sure delegation token gets propagated to Observer first before
Observer node reacts to a msync call.
4. as mentioned as a TODO in the WIP patch, still missing the logic to trigger
client making msync call when Observer node failover happens. Under the context
current WIP patch, this can be down by reseting AlignmentContext instance
stateid when switching observer in ProxyProvider.
These are based on discussions with [~shv], [~csun], [~zero45] and [~jnp],
thanks for the feedbacks!
> Introduce msync API call
> ------------------------
>
> Key: HDFS-13688
> URL: https://issues.apache.org/jira/browse/HDFS-13688
> Project: Hadoop HDFS
> Issue Type: Sub-task
> Reporter: Chen Liang
> Assignee: Chen Liang
> Priority: Major
> Attachments: HDFS-13688-HDFS-12943.WIP.002.patch,
> HDFS-13688-HDFS-12943.WIP.patch
>
>
> As mentioned in the design doc in HDFS-12943, to ensure consistent read, we
> need to introduce an RPC call {{msync}}. Specifically, client can issue a
> msync call to Observer node along with a transactionID. The msync will only
> return when the Observer's transactionID has caught up to the given ID. This
> JIRA is to add this API.
--
This message was sent by Atlassian JIRA
(v7.6.3#76005)
---------------------------------------------------------------------
To unsubscribe, e-mail: [email protected]
For additional commands, e-mail: [email protected]
