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https://issues.apache.org/jira/browse/HDFS-13688?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=16553676#comment-16553676
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Konstantin Shvachko commented on HDFS-13688:
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# As [previously
discussed|https://issues.apache.org/jira/browse/HDFS-12977?focusedCommentId=16368689&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16368689]
there is a constant {{HdfsServerConstants.INVALID_TXID}} for
{{INVALID_STATEID}}. But I don't think you need it in {{AlignmentContext}} at
all. If Server ever returns {{INVALID_TXID}}, you will catch it with {{((txid <
clientId)}} condition but not the other one, since it never equals
{{Long.MIN_VALUE}}.
# On the client we should always address {{ClientGSIContext}} instead of
{{AlignmentContext}}. The former already has {{getLastSeenStateId()}}. So you
don't need to add it to {{AlignmentContext}}. On the server
{{getLastSeenStateId()}} doesn't make sense.
# We should not just create a {{ClientGSIContext}} instance in DFSClient. It
lives deep inside {{ObserverReadProxyProvider}} and is generally not exposed to
DFSClient. You mostly use it for testing, but there should another way.
HDFS-13399 was dedicated to this. [This is the relevant
comment|https://issues.apache.org/jira/browse/HDFS-13399?focusedCommentId=16459341&page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel#comment-16459341].
There was also discussion around it in HDFS-12976.
I see you are passing it into {{ObserverReadProxyProvider}}, which we were
trying to avoid it in previous steps.
These are the main issues. I also see some unused imports and non-parameterized
generics.
> 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-12943.001.patch,
> HDFS-13688-HDFS-12943.002.patch, HDFS-13688-HDFS-12943.002.patch,
> 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.
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