Bug 568650

+++ This bug was initially created as a clone of Bug #568356 +++

Created an attachment (id=396283)
Test case

Description of problem:
Inside my CPG application, The confchg callback is called with 'dead'
members:

[debug] cpg member node 3 pid 1132
[debug] cpg member node 3 pid 14640

for example process 1132 does not exists any longer on node 3.


Version-Release number of selected component (if applicable):
TRUNK

How reproducible:
We have reliable reproducer in attachment.

Steps to Reproduce:
1. gcc -Wall cpgtest.c $(shell pkg-config --cflags --libs libcpg libcoroipcc) -o cpgtest
2. keep it run
  
Actual results:
# cpgtest
...
starting cpgtest
calling cpg_initialize
calling cpg_join
starting main loop (hangs here)

Expected results:
Never hang

Additional info:
Taken from OpenAIS mailing list

--- Additional comment from jfriesse on 2010-02-25 09:53:26 EST ---

Created an attachment (id=396287)
Proposed patch

Cpg join with undelivered leave message

Patch handles situation, when on one node, one process:
- join cpg
- do same actions
- leave cpg
- join cpg again

Following sequence can (racy) end with broken process_info list.

To solve this problem, one more check is done in
message_handler_req_lib_cpg_join so if process_info with same pid and
group as new join request exists, CPG_ERR_EXIST is returned.

--- Additional comment from dietmar on 2010-02-26 03:41:46 EST ---

works - no more ghost members.

But how can i handle CPG_ERR_EXIST correctly? 
Simply call join again seems to work:

	while ((result = cpg_join(handle, &group_name)) == CS_ERR_TRY_AGAIN ||
		result == CPG_ERR_EXIST ) { 
		printf("cpg_join returned %d\n", result);
		sleep (1);
	}

or is there a better way?

--- Additional comment from jfriesse on 2010-02-26 03:50:11 EST ---

(In reply to comment #2)
> works - no more ghost members.
> 
> But how can i handle CPG_ERR_EXIST correctly? 
> Simply call join again seems to work:
> 
>  while ((result = cpg_join(handle, &group_name)) == CS_ERR_TRY_AGAIN ||
>   result == CPG_ERR_EXIST ) { 
>   printf("cpg_join returned %d\n", result);
>   sleep (1);
>  }
> 
> or is there a better way?    

Hi,
thanks for very good news.

About handling. From my point of view, returning CPG_ERR_EXIST is not best way, I will "rework" patch to return CS_ERR_TRY_AGAIN because this is exactly what we need to return in such situations.

--- Additional comment from jfriesse on 2010-02-26 04:13:27 EST ---

Created an attachment (id=396497)
Proposed patch - returns err_try_again

Better version of patch, which return CPG_ERR_TRY_AGAIN rather than ERR_EXISTS.