Re: pipe chunking vs Windows

Magnus Hagander wrote:
> Andrew Dunstan wrote:
>
>>>> I have just discovered that the recently implemented pipe chunking
>>>> protocol is broken on Windows. This is because the pipes are operating
>>>> in text mode and doing LF->CR-LF translation, so the number of bytes
>>>> received is not the number transmitted and set in the protocol header.
>>>>
>>>> I have not yet succeeded in turning this behaviour off (_setmode()
>>>> didn't seem to affect it). If we can't find a way to turn it off, the
>>>> only solution short of abandoning its use on Windows that I can think of
>>>> is to translate LF on input to something unlikely like 0x1C and then
>>>> translate it back when we read it from the pipe.
>>>>
>>>>
>>> At what point does it actually do the translation? Meaning what
>>> system/library call has it?
>>>
>>> Are we using the pipes from src/port/pipe.c? It does sound a bit weird
>>> that they'd do that, since it's basically just emulating stuff over
>>> standard tcp sockets, but perhaps something is broken in that code?
>>>
>>> Sorry, haven't really checked up on the chunk code yet, so I don't know
>>> offhand where to look.
>>>
>>>
>>>
>>>
>> It looks like we aren't. In fact. it looks like the only call to
>> pgpipe() in the whole source tree is in the syslogger and it's in
>> specifically non-Windows code, meaning that that whole file is currently
>> useless.
>>
>
> Uh, see port.h, lines 212-224. If you're using the pipe() command to
> create it, it's used.
>

No, it's the other way around :-) If you use pgpipe() on Unix you're
calling pipe():

#ifndef WIN32
/*
* The function prototypes are not supplied because every C file
* includes this file.
*/
#define pgpipe(a) pipe(a)
#define piperead(a,b,c) read(a,b,c)
#define pipewrite(a,b,c) write(a,b,c)
#else
extern int pgpipe(int handles[2]);
extern int piperead(int s, char *buf, int len);

#define pipewrite(a,b,c) send(a,b,c,0)

#define PG_SIGNAL_COUNT 32
#define kill(pid,sig) pgkill(pid,sig)
extern int pgkill(int pid, int sig);
#endif

>
>
>> Maybe you should have a good look at src/backend/postmaster/syslogger.c.
>> If we could get rid of the pipe-read threads and all the special Windows
>> cruft there that would certainly be an advance.
>>
>
> I'll try to squeeze some time in to do that - I'll have to read up on
> the whole pipe/chunk thing first though, so it'll be a while.
>
>

You don't need to understand the protocol (it's a very simple
packetising protocol). The important point is that we have an anonymous
pipe (created with CreatePipe) which has been dup'ed into stderr.

cheers

andrew