[ClusterLabs] Upgrade corosync problem

[Jan Pokorný]

On 29/06/18 10:00 +0100, Christine Caulfield wrote:
> On 27/06/18 08:35, Salvatore D'angelo wrote:
>> One thing that I do not understand is that I tried to compare corosync
>> 2.3.5 (the old version that worked fine) and 2.4.4 to understand
>> differences but I haven’t found anything related to the piece of code
>> that affects the issue. The quorum tool.c and cfg.c are almost the same.
>> Probably the issue is somewhere else.
>> 
> 
> This might be asking a bit much, but would it be possible to try this
> using Virtual Machines rather than Docker images? That would at least
> eliminate a lot of complex variables.

Salvatore, you can ignore the part below, try following the "--shm"
advice in other part of this thread.  Also the previous suggestion
to compile corosync with --small-memory-footprint may be of help,
but comes with other costs (expect lower throughput).


Chrissie, I have a plausible explanation and if it's true, then the
same will be reproduced wherever /dev/shm is small enough.

If I am right, then the offending commit is
https://github.com/corosync/corosync/commit/238e2e62d8b960e7c10bfa0a8281d78ec99f3a26
(present since 2.4.3), and while it arranges things for the better
in the context of prioritized, low jitter process, it all of
a sudden prevents as-you-need memory acquisition from the system,
meaning that the memory consumption constraints are checked immediately
when the memory is claimed (as it must fit into dedicated physical
memory in full).  Hence this impact we likely never realized may
be perceived as a sort of a regression.

Since we can calculate the approximate requirements statically, might
be worthy to add something like README.requirements, detailing how much
space will be occupied for typical configurations at minimum, e.g.:

- standard + --small-memory-footprint configuration
- 2 + 3 + X nodes (5?)
- without any service on top + teamed with qnetd + teamed with
  pacemaker atop (including just IPC channels between pacemaker
  daemons and corosync's CPG service, indeed)

-- 
Jan (Poki)
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