[jira] [Created] (HDFS-16821) HDFS clients must not use ClientGSIContext unless explicit configured to do so.

["Simbarashe Dzinamarira (Jira)" <ji...@apache.org>]

Simbarashe Dzinamarira created HDFS-16821:
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             Summary: HDFS clients must not use ClientGSIContext unless explicit configured to do so.
                 Key: HDFS-16821
                 URL: https://issues.apache.org/jira/browse/HDFS-16821
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: hdfs
            Reporter: Simbarashe Dzinamarira


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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