pratapaditya04 opened a new pull request, #4184:
URL: https://github.com/apache/gobblin/pull/4184

   Dear Gobblin maintainers,
   
   Please accept this PR. I understand that it will not be reviewed until I 
have checked off all the steps below!
   
   
   ### JIRA
   - [ ] My PR addresses the following [Gobblin 
JIRA](https://issues.apache.org/jira/browse/GOBBLIN/) issues and references 
them in the PR title. For example, "[GOBBLIN-XXX] My Gobblin PR"
       - https://issues.apache.org/jira/browse/GOBBLIN-XXX
   
   
   ### Description
   - [ ] Here are some details about my PR, including screenshots (if 
applicable):
   
     We observed a production incident where the Commit activity hung for 4.5h 
in
     `DFSClient.close()` → `Client.stop()` → `Object.wait()` with no way to 
unblock.                                                                        
                                          
     `Client.stop()` waits indefinitely for all in-flight RPC calls to drain — 
for
     reasons still not fully understood, this call never returned.              
                                                                                
                                      
                                                               
     One likely contributing factor: `Help.loadFileSystem()` returns a 
cached/shared                                                                   
                                               
     `FileSystem` instance. The underlying `DFSClient` and Hadoop IPC `Client` 
are
     shared across all activities on the same Temporal worker. The worker 
handles                                                                         
                                            
     multiple concurrent workflow executions — so while this workflow's 
CommitActivity
     closes the FS, a different workflow's ProcessWorkUnit activities (or their 
background                                                                      
                                      
     threads) may still have in-flight HDFS calls through the same shared 
client.                                                                         
                                            
     `Client.stop()` would then wait for those calls to drain too, not just its 
own,                                                                            
                                      
     potentially hanging indefinitely.                                          
                                                                                
                                      
                                                                                
                                                                                
                                      
     TODO: root cause not fully confirmed — an underlying NameNode/IPC issue 
cannot                                                                          
                                         
     be ruled out and is being investigated in parallel with the HDFS team. 
   ### Tests
   - [ ] My PR adds the following unit tests __OR__ does not need testing for 
this extremely good reason:
   
   
   ### Commits
   - [ ] My commits all reference JIRA issues in their subject lines, and I 
have squashed multiple commits if they address the same issue. In addition, my 
commits follow the guidelines from "[How to write a good git commit 
message](http://chris.beams.io/posts/git-commit/)":
       1. Subject is separated from body by a blank line
       2. Subject is limited to 50 characters
       3. Subject does not end with a period
       4. Subject uses the imperative mood ("add", not "adding")
       5. Body wraps at 72 characters
       6. Body explains "what" and "why", not "how"
   
   


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