Hi Hermant,
On Fri, Sep 14, 2018 at 1:53 PM Hemant Chaudhary
<hemantdude.chaudhary@xxxxxxxxx> wrote:
>
> Please don't get confuse with Cygwin(Windows). I am running apache on NonStop(Tandem).
Well, isn't the error_log attached to the previous message relevant
(be it cygwin or not)?
Btw, LogLevel trace6 would help here.
> I have put breakpoint at apr_poll() but it is not going there.
>
> Few Events of writing :
> 1) apache writes 779 bytes to tomcat from apr_socket_sendv() function and writev functions returns success.
> 2) apache writes 24604 bytes to tomcat from apr_socket_sendv() function but writev function returns -1 with EWOULDBLOCK and it has timeout=0(because set in writev_nonblocking())
> 3) apache again tries to write 32796 to tomcat from apr_socket_sendv() function but writev function returns -1 with EWOULDBLOCK and it has timeout=0(because set in writev_nonblocking()).
> 4) apache again tries to write 40988 to tomcat from apr_socket_sendv() function but writev function returns -1 with EWOULDBLOCK and it has timeout=0(because set in writev_nonblocking()).
> 5) apache again tries to write 49180 to tomcat from apr_socket_sendv() function but writev function returns -1 with EWOULDBLOCK and it has timeout=0(because set in writev_nonblocking()).
OK, all those EWOULDBLOCK make the core output filter to bufferize the
"pending" data for the next time it's called.
> 6) After this I am getting 4022 error.
Here the 64K bufferized limit/threshold is reached
(non_file_bytes_in_brigade >= THRESHOLD_MAX_BUFFER in
ap_core_output_filter()), so the core output filter can't continue
nonblocking anymore and enters send_brigade_blocking(), which does
send_brigade_nonblocking() + apr_poll() until the 64K buffer is sent
completely.
However it seems that on your system the first call to
send_brigade_nonblocking() fails (since apr_poll() is never called),
possibly a limit on apr_socket_sendv() (i.e. writev() syscall), either
more than 64K total bytes or nvec > 4?
I think you need to debug/gdb in send_brigade_nonblocking() for this
last call and determine where and why send_brigade_nonblocking() =>
writev_nonblocking() => apr_socket_send() => writev(vec, nvec) fails.
Maybe a unit test (a simple standalone main() program) can determine
the limits for writev() on your system, so that the right values for
THRESHOLD_MAX_BUFFER and MAX_IOVEC_TO_WRITE (in
"server/core_filters.c") can be tuned for NonStop(Tandem) ...
Hope that helps,
Yann.
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