tanvipenumudy opened a new pull request, #5322:
URL: https://github.com/apache/ozone/pull/5322

   ## What changes were proposed in this pull request?
   
   After the implementation of 
[HDDS-8300](https://issues.apache.org/jira/browse/HDDS-8300), get key metadata 
API in OM sorts datanodes to allow clients to optimize data I/O based on 
locality. However, as of today, this requires OM to make additional calls to 
SCM for sorting the datanodes. 
   
   The get key metadata API makes 2 separate calls to SCM: one to retrieve the 
container pipelines and the second responsible for sorting the datanodes in the 
container pipelines, as illustrated in the code snippet 
[KeyManagerImpl#getKeyInfo](https://github.com/apache/ozone/blob/master/hadoop-ozone/ozone-manager/src/main/java/org/apache/hadoop/ozone/om/KeyManagerImpl.java#L1946-L1959):
 
   ```
   if (!args.isHeadOp()) {
   ...
         // get container pipeline info from cache.
         captureLatencyNs(metrics.getGetKeyInfoRefreshLocationLatencyNs(),
             () -> refreshPipelineFromCache(value,
                 args.isForceUpdateContainerCacheFromSCM()));
   
         if (args.getSortDatanodes()) {
           sortDatanodes(clientAddress, value);
         }
   ```
   
   For performance enhancement, these two calls can be combined into one 
allowing the result to be cached in the existing `containerLocationCache` in 
`ScmClient`. More details on the analysis and implementation can be found 
[here](https://issues.apache.org/jira/browse/HDDS-9272).
   
   ## What is the link to the Apache JIRA
   
   https://issues.apache.org/jira/browse/HDDS-9272
   
   ## How was this patch tested?
   
   The existing tests should cover the changes.
   


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