Re: [naviserver-devel] Writer thread question

[Vlad S. <vl...@cr...>]

Ns_SockSendBufs() is not supposed to send all at once, that is the 
problem. That's why small change i sent to Bernd should fix it, i just 
do not want to commit it before the test.

Stephen Deasey wrote:
> On 11/7/06, Zoran Vasiljevic <zv...@ar...> wrote:
>> On 07.11.2006, at 17:02, Bernd Eidenschink wrote:
>>
>>> I set logmaxlevel to 6 (dev) and I sometimes see lines like:
>>>
>>> Debug: SockSend: Resource temporarily unavailable
>>> Debug: SockSend: Resource temporarily unavailable
>>> (...)
>> Out of the blue, I would not consider this a problem.
>> This is reading on an non-blocking socket that has no
>> bytes in the buffer. Some OS'es emit EAGAIN some
>> EWOULDBLOCK on that place (aparently this OS does EAGAIN).
> 
> 
> It's writing, not reading...  :-)
> 
> Anyway, this is actually an error, in the case of the writer thread at
> least. In nsd/driver.c the writer thread calls Ns_SockSendBufs() and
> if the return value is not the full amount, an error condition is
> signalled.
> 
> I added the debug message because looking at the way code was calling
> Ns_SockSendBufs() (or Ns_SockSend(), which actually doesn't have this
> logging message, oops), it was expecting the call to succeed. This
> wrapper function actually retries to send the data if the first
> attempt fails, but it only retries *once*, and then it gives up.
> 
> If you see the above message then I believe the writer thread failed
> to send all it's data and gave up.
> 
> I don't think the API is great. It confuses the issue of who's
> responsible for ensuring data gets written. Is Ns_SockSend* supposed
> to send all the data or not?  I guess the issue is fudged because all
> the socket is in non-blocking mode, because the read-side does in fact
> do non blocking reads, the write side was always called by a conn
> thread and was expecting to write everything before returning.
> 
> That isn't the case now that there is the writer thread stuff. But
> either way it's still broken. It sort of half promises to send stuff.
> Two attempts and then it gives up...
> 
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-- 
Vlad Seryakov
571 262-8608 office
vl...@cr...
http://www.crystalballinc.com/vlad/