[jira] [Commented] (THRIFT-1642) Miscalculation lead to throw unexpected "TTransportException::TIMED_OUT"(or called "EAGAIN (timed out)") exception

["David Nadlinger (JIRA)" <ji...@apache.org>]

    [ https://issues.apache.org/jira/browse/THRIFT-1642?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13406442#comment-13406442 ] 

David Nadlinger commented on THRIFT-1642:
-----------------------------------------

The point of the {{usleep}} call is to avoid busy-spinning if the system might already be in need of some CPU power to handle networking. {{eagainThresholdMicros}} is explained in the comment right above the line you changed.
                
> Miscalculation lead to throw unexpected "TTransportException::TIMED_OUT"(or called "EAGAIN (timed out)") exception
> ------------------------------------------------------------------------------------------------------------------
>
>                 Key: THRIFT-1642
>                 URL: https://issues.apache.org/jira/browse/THRIFT-1642
>             Project: Thrift
>          Issue Type: Bug
>          Components: C++ - Library
>    Affects Versions: 0.8
>         Environment: GNU/Linux x86_64
>            Reporter: catxl
>            Priority: Critical
>         Attachments: TSocket.cpp.patch
>
>   Original Estimate: 1h
>  Remaining Estimate: 1h
>
> In function 'uint32_t TSocket::read(uint8_t* buf, uint32_t len)', there's an miscalculation which can lead to wrong judgment:
> struct timeval begin;
> gettimeofday(&begin, NULL);
> //
> // do some thing
> //
> struct timeval end;
> gettimeofday(&end, NULL);
> uint32_t readElapsedMicros =  (((end.tv_sec - begin.tv_sec) * 1000 * 1000)
>                                + (((uint64_t)(end.tv_usec - begin.tv_usec))));
> 'readElapsedMicros' will be very large when 'end.tv_usec < begin.tv_usec'.
> This will lead to throw unexpected "TTransportException::TIMED_OUT"(or called "EAGAIN (timed out)") exception sometimes.
> Besides, 
> (1)I don't think the "usleep(50);" call in the same function above is necessary, I think delete this call could improve performance.
> (2)I don't know why 'readElapsedMicros' compare with 'eagainThresholdMicros', which is not the value (recvTimeout_*1000), but:
>    eagainThresholdMicros = (recvTimeout_*1000)/ ((maxRecvRetries_>0) ? maxRecvRetries_ : 2);
>    can anyone tell me someting about this? Thank you!

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