maria-developers team mailing list archive

[Paul McCullagh <paul.mccullagh@xxxxxxxxx>]

Hi All,

Yes, PBXT uses a lot of file handles: generally 3 per table. It opens  
all tables before recovery. Unfortunately, I have not worked on  
optimizing this behavior.

Although the only reason for this is to resolve possible FK/PK  
relationships. So I think this should be considered a PBXT bug, and  
the problem should be fixed.

Anyway this will certainly be the problem in this case. As Kristian  
says, select() is severely limited in that it only works with the low  
numbered file handles.

To get the server up and running again you can just delete the tables  
manually (the table files: .frm, .xtd, .xtr, .xti), when MySQL is not  
running. PBXT will complain on startup, but should recover anyway.

Best regards,

Paul

On Jul 15, 2010, at 9:48 AM, Michael Widenius wrote:

> Hi!
>
> > > > > > "Time" == Time Less <timelessness@xxxxxxxxx> writes:
>
> > > I think it is very likely that you are hitting this bug:
> > >
> > > http://bugs.mysql.com/bug.php?id=48929
>
> Time> Ah, yes, could be. Though my strace was different than this  
> bug shows.
>
>
> > > The problem is that MySQL/MariaDB is using select() to accept new
> > > connections. But select() has a hard-coded limit of 1024 on the  
> > > max number
> > > of
> > > open files it can support. It seems PBXT uses an open file  
> > > descriptor per
> > > table,
>
>
> Time> Not two per table? It has it looks like many log files, then  
> also a data and
> Time> index file per table. On my system where I'm trying to use  
> 1,000 tables, I
> Time> expect about 2,000+[mumble] file handles.
>
> > > Maybe MariaDB should backport the fix, it is actually a buffer  
> > > overflow
> > > (though it is hard to see how it could be exploitable), but  
> > > perhaps more
> > > relevant it is a rather nasty state for the server to get into,  
> > > and not
> > > really
> > > clear how to get it out of it again :-(.
>
> Time> You can't get out of the state again. The server won't accept  
> connections,
> Time> so you can't drop any tables. You just have to wipe the DB and  
> start over.
> Time> If PBXT is resilient to its tables disappearing between server  
> restarts, you
> Time> could rm files from the data directory.
>
> I didn't know that PBXT would open up all files at startup. If that's
> the case, we should switch to use poll in MariaDB 5.3 ASAP (and
> provide a patch for those that wants it for MariaDB 5.1).
>
> Paul, can you verify the above is the case for PBXT (ie, that PBXT
> uses one file descriptor per table and don't free these at all?)
>
> Regards,
> Monty
>
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