On Mon, Oct 12, 2015 at 4:42 PM, Dmitry Vasilyev <d.vasil...@postgrespro.ru> wrote:
> Hello, Amit! > > On Пн, 2015-10-12 at 11:25 +0530, Amit Kapila wrote: > > On Sun, Oct 11, 2015 at 9:12 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > > > Magnus Hagander <mag...@hagander.net> writes: > > > On Sun, Oct 11, 2015 at 5:22 PM, Tom Lane <t...@sss.pgh.pa.us> wrote: > > >> I'm a bit suspicious that we may have leaked a handle to the shared > > >> memory block someplace, for example. That would explain why this > > >> symptom is visible now when it was not in 2009. Or maybe it's > dependent > > >> on some feature that we didn't test back then --- for instance, if > > >> the logging collector is in use, could it have inherited a handle and > > >> not closed it? > > > > > Even if we leaked it, it should go away when the other processes died. > > > > I'm fairly certain that we do not kill/restart the logging collector > > during a database restart (because it's impossible to reproduce the > > original stderr destination if we do). > > True and it seems this is the reason for issue we are discussing here. > The reason why this happens is that during creation of shared memory > (PGSharedMemoryCreate()), we duplicate the handle such that it > become inheritable by all child processes. Then during fork > (syslogger_forkexec()->postmaster_forkexec()->internal_forkexec) we > always inherit the handles which causes syslogger to get a copy of > shared memory handle which it neither uses and nor closes it. > > I could easily reproduce the issue if logging collector is on and even if > we try to increase the loop count or sleep time in PGSharedMemoryCreate(), > it doesn't change the situation as the syslogger has a valid handle to > shared memory. One way to fix is to just close the shared memory handle > in sys logger as we are not going to need it and attached patch which does > this fixes the issue for me. Another invasive fix in case we want to > retain shared memory handle for some purpose (future requirement) could > be to send some signal to syslogger in restart path so that it can release > the shared memory handle. > > > > With Regards, > Amit Kapila. > EnterpriseDB: http://www.enterprisedb.com > > > Specified patch with "ifdef WIN32" is working for me. Maybe it’s necessary > to check open handlers from replication for example? > > Assuming the problem will be fixed, should we release Beta2 soon ? > > -------------- > Dmitry Vasilyev > Postgres Professional: http://www.postgrespro.com > The Russian Postgres Company >
