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Posted to hdfs-dev@hadoop.apache.org by "Takanobu Asanuma (Jira)" <ji...@apache.org> on 2023/02/01 06:00:00 UTC
[jira] [Resolved] (HDFS-16821) Fix regression in HDFS-13522 that enables observer reads by default.
[ https://issues.apache.org/jira/browse/HDFS-16821?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel ]
Takanobu Asanuma resolved HDFS-16821.
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Fix Version/s: 3.4.0
Resolution: Fixed
> Fix regression in HDFS-13522 that enables observer reads by default.
> --------------------------------------------------------------------
>
> Key: HDFS-16821
> URL: https://issues.apache.org/jira/browse/HDFS-16821
> Project: Hadoop HDFS
> Issue Type: Bug
> Components: hdfs
> Reporter: Simbarashe Dzinamarira
> Assignee: Simbarashe Dzinamarira
> Priority: Major
> Labels: pull-request-available
> Fix For: 3.4.0
>
>
> Serving reads consistently from Observer Namenodes is a feature that was introduced in HDFS-12943.
> Clients opt-into this feature by configuring the ObserverReadProxyProvider. It is important that the opt-in is explicit because for third-party reads to remain consistent, these clients then need to perform an msync before reads.
> In HDFS-13522, the ClientGSIContext is implicitly added to the DFSClient thus enabling Observer reads for all clients by default. This breaks consistency guarantees for clients that haven't opted into observer reads.
> [https://github.com/apache/hadoop/pull/4883/files#diff-a627e2c1f3e68235520d3c28092f4ae8a41aa4557cc530e4e6862c318be7e898R352-R354]
> We need to return to the old behavior of only using the ClientGSIContext when users have explicitly opted into Observer reads.
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