Xieming Li commented on HDFS-15024:

Is it a bad idea to retry immediately on StandbyException?

> [SBN read] In FailoverOnNetworkExceptionRetry , Number of NameNodes as a 
> condition of calculation of sleep time
> ---------------------------------------------------------------------------------------------------------------
>                 Key: HDFS-15024
>                 URL: https://issues.apache.org/jira/browse/HDFS-15024
>             Project: Hadoop HDFS
>          Issue Type: Improvement
>    Affects Versions: 2.10.0, 3.3.0, 3.2.1
>            Reporter: huhaiyang
>            Priority: Major
>         Attachments: HDFS-15024.001.patch, client_error.log
> When we enable the ONN , there will be three NN nodes for the client 
> configuration,
> Such as configuration
> <property>
>     <name>dfs.ha.namenodes.ns1</name>
>     <value>nn2,nn3,nn1</value>
> </property>
> Currently, 
> nn2 is in standby state
> nn3 is in observer state 
> nn1 is in active state
> When the user performs an access HDFS operation
> ./bin/hadoop --loglevel debug fs 
> -Ddfs.client.failover.proxy.provider.ns1=org.apache.hadoop.hdfs.server.namenode.ha.ObserverReadProxyProvider
>  -mkdir /user/haiyang1/test8
> You need to request nn1 when you execute the msync method,
> Actually connect nn2 first and failover is required
> In connection nn3 does not meet the requirements, failover needs to be 
> performed, but at this time, failover operation needs to be performed during 
> a period of hibernation
> Finally, it took a period of hibernation to connect the successful request to 
> nn1
> In FailoverOnNetworkExceptionRetry getFailoverOrRetrySleepTime The current 
> default implementation is Sleep time is calculated when more than one 
> failover operation is performed
> I think that the Number of NameNodes as a condition of calculation of sleep 
> time is more reasonable
> That is, in the current test, executing failover on connection nn3 does not 
> need to sleep time to directly connect to the next nn node
> See client_error.log for details

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