[Pgpool-general] pgpool 2.2.4: DEALLOCATED children

[Tatsuo Ishii]

Agustín,

> > > Hi
> > > 
> > > We applied the patch with the same result. After some
> > seconds child  
> > > processes go into DEALLOCATE state until pgpool gets
> > completly hang.

[snip]

> > > i attached the complete log for one of these
> > processes.
> > > 
> > > 
> > > Please any test we can do to help the analsys just let
> > us know.
> > 
> > It seems cause of this is, pgpool sends BEGIN to PostgreSQL
> > and
> > PostgreSQL replies ERROR for unknown reason. I need to know
> > why
> > PostgreSQL emits ERROR. Can you find error messages in the
> > PostgreSQL
> > log?

Ok, I think for some reason DEALLOCATE fails and the internal list
which manages prepared objects is not updated, and same request is
issued over and over again. I need to know why DEALLOCATE fails, but
at least we should prepare for this kind of cases. Attached patches
implement this. Please try if you like.

Glyn,

> We saw a similar(ish) issue here where a pgpool backend went into an aparent infinite loop sending the same dealocate statement to the postgres server, but I couldn't reproduce it at the time.
> 
> However this was on 2.2.3, and at the same time as moving to 2.2.3 I changed reset_query_list to 'ABORT; DISCARD ALL'.
> 
> The next day 2.2.4 was released so we upgraded and I switched reset_query_list back to 'ABORT; RESET ALL; SET SESSION AUTHORIZATION DEFAULT'.
> 
> I've not seen any issues since, using 'ABORT; DISCARD ALL' has always caused problems for me though.

What kind of problem do you have with DISCARD ALL?
--
Tatsuo Ishii
SRA OSS, Inc. Japan
-------------- next part --------------
Index: pool_process_query.c
===================================================================
RCS file: /cvsroot/pgpool/pgpool-II/pool_process_query.c,v
retrieving revision 1.141.2.19
diff -c -r1.141.2.19 pool_process_query.c
*** pool_process_query.c	17 Sep 2009 11:17:09 -0000	1.141.2.19
--- pool_process_query.c	23 Sep 2009 11:08:33 -0000
***************
*** 1755,1761 ****
  		pool_write(frontend, &kind, 1);
  		sendlen = htonl(len1+4);
  		pool_write(frontend, &sendlen, sizeof(sendlen));
! 		status = pool_write(frontend, p1, len1);
  	}
  
  	/* save the received result for each kind */
--- 1755,1761 ----
  		pool_write(frontend, &kind, 1);
  		sendlen = htonl(len1+4);
  		pool_write(frontend, &sendlen, sizeof(sendlen));
! 		pool_write(frontend, p1, len1);
  	}
  
  	/* save the received result for each kind */
***************
*** 1863,1870 ****
  			ret = SimpleForwardToFrontend(kind1, frontend, backend);
  			if (ret != POOL_CONTINUE)
  				return ret;
! 			if (pool_flush(frontend))
! 				return POOL_END;
  		}
  
  		if (ret != POOL_CONTINUE)
--- 1863,1869 ----
  			ret = SimpleForwardToFrontend(kind1, frontend, backend);
  			if (ret != POOL_CONTINUE)
  				return ret;
! 			pool_flush(frontend);
  		}
  
  		if (ret != POOL_CONTINUE)
***************
*** 2035,2043 ****
  		}
  
  		/*
! 		 * Describe message with a portal name receive two messages.
  		 * 1. ParameterDescription
  		 * 2. RowDescriptions or NoData
  		 */
  		if (kind == 'D' && *p == 'S')
  		{
--- 2034,2043 ----
  		}
  
  		/*
! 		 * Describe message with a portal name will receive two messages.
  		 * 1. ParameterDescription
  		 * 2. RowDescriptions or NoData
+ 		 * So we read one message here.
  		 */
  		if (kind == 'D' && *p == 'S')
  		{
***************
*** 2049,2054 ****
--- 2049,2057 ----
  				return POOL_END;
  		}
  
+ 		/*
+ 		 * Forward to frontend until a NOTICE message received.
+ 		 */
  		for (;;)
  		{
  			ret = read_kind_from_backend(frontend, backend, &kind1);
***************
*** 2166,2172 ****
  			return 2;
  		}
  
! 		send_deallocate(backend, &prepared_list, 0);
  		return 1;
  	}
  
--- 2169,2183 ----
  			return 2;
  		}
  
! 		/* Delete from prepared list */
! 		if (send_deallocate(backend, &prepared_list, 0))
! 		{
! 			/* Deallocate failed. We are in unknown state. Ask caller
! 			 * to reset backend connection.
! 			 */
! 			reset_prepared_list(&prepared_list);
! 			return -1;
! 		}
  		return 1;
  	}