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https://issues.apache.org/jira/browse/HDDS-14379?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=18051404#comment-18051404
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Ivan Andika commented on HDDS-14379:
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[~greenwich] Thanks for checking with this.
> What about adding `GrpcOMFollowerReadProxyProvider` that wraps
> `GrpcOMFailoverProxyProvider`?
Currently, I am focusing on getting the Hadoop RPC implementation working
first. I am not too familiar with gRPC failover proxy provider implementation,
but the follower read proxy provider follows the architecture of Hadoop's
ObserverReadProxyProvider, so I'm not sure whether it can be adapted in the
future.
> Any specs available? Any help required? :)
Currently, we are working on the implementation based on our internal spec,
will share with the community if it works.
> Implement basic Hadoop OM client proxy provider to read from followers
> ----------------------------------------------------------------------
>
> Key: HDDS-14379
> URL: https://issues.apache.org/jira/browse/HDDS-14379
> Project: Apache Ozone
> Issue Type: New Feature
> Components: OM HA, Ozone Client
> Reporter: Ivan Andika
> Assignee: Ivan Andika
> Priority: Major
>
> This task is to come up with the basic implementation of follower read client
> proxy as a baseline before further performance improvements. The idea is to
> simply pick a OM node in random (which be leader or follower / listener) and
> use it to submit read requests. If the chosen OM node is a follower, the read
> requests need to keep sending to that OM node unless the OM is down which
> triggers failover. Write requests should be sent to the OM leader directly.
> Further improvements such as adding OM probe logic will be implemented in
> follow up tasks.
> The implementation is to introduce HadoopRpcOMFollowerReadProxyProvider which
> wraps
> HadoopRpcOMFailoverProxyProvider. FollowerReadProxyProvider tracks a
> different currentOmNodeId from HadoopRpcOMFailoverProxyProvider.
> FollowerReadInvocationHandler will check whether the request is a read
> request (using OmUtils#isReadOnly) and if so forwards it to its current
> proxy. If it's a write request, the request if forwarded to
> HadoopRpcOMFailoverProxyProvider to be sent to the leader.
> So the proxy hierarchy is
> * TracingProxy
> ** RetryProxy
> *** HadoopRpcOMFollowerReadProxyProvider
> **** HadoopRpcOMFailoverProxyProvider
>
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