[jira] [Created] (HDFS-14272) [SBN read] HDFS command line tools does not guarantee consistency

["Wei-Chiu Chuang (JIRA)" <ji...@apache.org>]

Wei-Chiu Chuang created HDFS-14272:
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             Summary: [SBN read] HDFS command line tools does not guarantee consistency
                 Key: HDFS-14272
                 URL: https://issues.apache.org/jira/browse/HDFS-14272
             Project: Hadoop HDFS
          Issue Type: Bug
          Components: tools
         Environment: CDH6.1 (Hadoop 3.0.x) + Consistency Reads from Standby + SSL + Kerberos + RPC encryption
            Reporter: Wei-Chiu Chuang


It is typical for integration tests to create some files and then check its existence. For example, like the following simple bash script:
{code:java}
# hdfs dfs -touchz /tmp/abc
# hdfs dfs -ls /tmp/abc
{code}
The test execute HDFS bash command sequentially, but it may fail with Consistent Standby Read because the -ls may not find the file.

Analysis: the second bash command, while launched sequentially after the first one, is not aware of the state id returned from the first bash command. So ObserverNode wouldn't wait for the the edits to get propagated, and thus fails.

I've got a cluster where the Observer has tens of seconds of RPC latency, and this becomes very annoying. (I am still trying to figure out why this Observer has such a long RPC latency. But that's another story.)



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