Re: [Sqlrelay-discussion] short write

[Matt F. <ma...@eq...>]

in my case it sounds like non-blocking mode, short write loops 
forever...or at least longer than I have patience to wait to see if it 
completes.

Firstworks/4access wrote:

>Now I remember that code :)
>
>To improve performance, the filedescriptor class supports buffered reads
>and writes.  SQL Relay sets up an 8k buffer for both read and write
>buffers on both server and client sides.  When one side tries to write()
>to the other, the data just gets buffered.  When the buffer is full or
>if flushWriteBuffer() is called, the entire buffer is sent over the
>network.  A short-write condition (ie. if an attempt to write 8192 bytes
>wrote fewer than 8192 bytes) can occur under several circumstances, most
>notably if some buffer in the kernel or in the underlying hardware is
>full, which can happen if the machine's network interfaces are really
>slammed.
>
>The code should just loop back and try to write the remaining data
>again.  Whether the file descriptor is in blocking or non-blocking mode
>could affect that though.  In blocking mode, when looping back and
>writing again, the write() will block until the device can accept data,
>but in non-blocking mode, the write() will fall through with another
>short-write condition which will loop back and retry again, over and
>over.  I'll have to think about that a little.
>
>Dave
>
>On Wed, 2005-08-24 at 11:45 -0400, Matt Flynn wrote:
>  
>
>>typo in original message: 'I assume...writebufferspace=8 are default 
>>values...' should be '...writebufferspace=0...'
>>
>>Matt Flynn wrote:
>>
>>    
>>
>>>I am receiving the message 'aaaah, short write!!!!!' from 
>>>librudiments.so using rudiments 0.28.2 and sqlrelay 0.36.4.
>>>
>>>I have enabled DEBUG_WRITE in rudiments-0.28.2/src/filedescriptor.C 
>>>and here is a sample of the output during error conditions:
>>>22687: string write(5,sjir,4)
>>>bufferedWrite of 4 bytes
>>>      writebuffersize=8192
>>>      writebufferspace=0
>>>      byteswritten=0
>>>      bytesunwritten=4
>>>just buffering 0 bytes
>>>safeWrite of 8192 bytes
>>>aaaaah, short write!!!!!
>>>22687: ushort write(5,1)
>>>bufferedWrite of 2 bytes
>>>      writebuffersize=8192
>>>      writebufferspace=0
>>>      byteswritten=0
>>>      bytesunwritten=2
>>>just buffering 0 bytes
>>>safeWrite of 8192 bytes
>>>aaaaah, short write!!!!!
>>>
>>>I assume writebuffersize=8192 and writebufferspace=8 are default 
>>>values.  Under normal working conditions writebuffersize is usually 
>>>less than 8192 and writebufferspace is always greater than 0.   
>>>Possibly memory not being initialized properly?  Possibly flaky 
>>>network card?
>>>
>>>Any suggestions?
>>>
>>>Thanks,
>>>
>>>Matt
>>>
>>>
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