[jira] [Created] (IMPALA-10139) Slow RPC logs can be misleading

["Sahil Takiar (Jira)" <ji...@apache.org>]

Sahil Takiar created IMPALA-10139:
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             Summary: Slow RPC logs can be misleading
                 Key: IMPALA-10139
                 URL: https://issues.apache.org/jira/browse/IMPALA-10139
             Project: IMPALA
          Issue Type: Improvement
            Reporter: Sahil Takiar


The slow RPC logs added in IMPALA-9128 are based on the total time taken to successfully complete a RPC. The issue is that there are many reasons why an RPC might take a long time to complete. An RPC is considered complete only when the receiver has processed that RPC. 

The problem is that due to client-driven back-pressure mechanism, it is entirely possible that the receiver RPC does not process a receiver RPC because {{KrpcDataStreamRecvr::SenderQueue::GetBatch}} just hasn't been called yet (indirectly called by {{ExchangeNode::GetNext}}).

This can lead to flood of slow RPC logs, even though the RPCs might not actually be slow themselves. What is worse is that the because of the back-pressure mechanism, slowness from the client (e.g. Hue users) will propagate across all nodes involved in the query.



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