[jira] [Created] (HADOOP-15840) Slow RPC logger too spammy

["Wei-Chiu Chuang (JIRA)" <ji...@apache.org>]

Wei-Chiu Chuang created HADOOP-15840:
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             Summary: Slow RPC logger too spammy
                 Key: HADOOP-15840
                 URL: https://issues.apache.org/jira/browse/HADOOP-15840
             Project: Hadoop Common
          Issue Type: Improvement
    Affects Versions: 3.0.0-alpha1, 2.7.4, 2.8.0
            Reporter: Wei-Chiu Chuang


HADOOP-12325 added a capability where "slow" RPCs are logged in NN log when ipc.server.log.slow.rpc is enabled.

The "slow" RPCs are supposed to be those whose processing time is outside 3 standard deviation, and it supposed to account for 0.3% of total RPCs.

However, I found in practice, NN marks more than 1% of total RPCs as slow, and I've seen RPCs whose processing time is 1ms declared slow too.
{noformat}
2018-10-08 01:48:33,203 WARN org.apache.hadoop.ipc.Server: Slow RPC : sendHeartbeat took 1 milliseconds to process from client 10.17.199.16:56645
2018-10-08 01:48:33,219 WARN org.apache.hadoop.ipc.Server: Slow RPC : sendHeartbeat took 1 milliseconds to process from client 10.17.190.44:36435
2018-10-08 01:48:33,308 WARN org.apache.hadoop.ipc.Server: Slow RPC : sendHeartbeat took 1 milliseconds to process from client 10.17.190.43:56530
{noformat}
This is too many. 1% means NN spits hundreds slow RPCs per second on average in NN log.

How about:
 # use 4 stddev?
 # use microsecond precision. Majority of RPCs takes less than 1 millisecond anyway. It makes the stddev calculation imprecise. An RPC could be calculated to spend 1 millisecond and be marked as "slow", since it starts from one millisecond and ends in the next millisecond.

 

[~anu] any thoughts?



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