[ClusterLabs Developers] OCF_RESKEY_CRM_meta_notify_active_* always empty

Ken Gaillot kgaillot at redhat.com
Fri Jul 29 22:51:52 UTC 2016


On 07/29/2016 05:41 PM, Andrew Beekhof wrote:
> 
> 
> Sent from my iPhone
> 
>> On 30 Jul 2016, at 8:32 AM, Ken Gaillot <kgaillot at redhat.com> wrote:
>>
>> I finally had time to investigate this, and it definitely is broken.
>>
>> The only existing heartbeat RA to use the *_notify_active_* variables is
>> Filesystem, and it only does so for OCFS2 on SLES10, which didn't even
>> ship pacemaker,
> 
> I'm pretty sure it did

All I could find was:

"SLES 10 did not yet ship pacemaker, but heartbeat with the builtin crm"

http://oss.clusterlabs.org/pipermail/pacemaker/2014-July/022232.html

I'm sure people were compiling it, and ClusterLabs probably even
provided a repo, but it looks like sles didn't ship it.

The issue is that the code that builds the active list checks for role
RSC_ROLE_STARTED rather than RSC_ROLE_SLAVE + RSC_ROLE_MASTER, so I
don't think it ever would have worked.

> 
>> so I'm guessing it's been broken from the beginning of
>> pacemaker.
>>
>> The fix looks straightforward, so I should be able to take care of it soon.
>>
>> Filed bug http://bugs.clusterlabs.org/show_bug.cgi?id=5295
>>
>>> On 05/08/2016 04:57 AM, Jehan-Guillaume de Rorthais wrote:
>>> Le Fri, 6 May 2016 15:41:11 -0500,
>>> Ken Gaillot <kgaillot at redhat.com> a écrit :
>>>
>>>>> On 05/03/2016 05:30 PM, Jehan-Guillaume de Rorthais wrote:
>>>>> Le Tue, 3 May 2016 21:10:12 +0200,
>>>>> Jehan-Guillaume de Rorthais <jgdr at dalibo.com> a écrit :
>>>>>
>>>>>> Le Mon, 2 May 2016 17:59:55 -0500,
>>>>>> Ken Gaillot <kgaillot at redhat.com> a écrit :
>>>>>>
>>>>>>>> On 04/28/2016 04:47 AM, Jehan-Guillaume de Rorthais wrote:
>>>>>>>> Hello all,
>>>>>>>>
>>>>>>>> While testing and experiencing with our RA for PostgreSQL, I found the
>>>>>>>> meta_notify_active_* variables seems always empty. Here is an example of
>>>>>>>> these variables as they are seen from our RA during a
>>>>>>>> migration/switchover:
>>>>>>>>
>>>>>>>>
>>>>>>>>  {
>>>>>>>>    'type' => 'pre',
>>>>>>>>    'operation' => 'demote',
>>>>>>>>    'active' => [],
>>>>>>>>    'inactive' => [],
>>>>>>>>    'start' => [],
>>>>>>>>    'stop' => [],
>>>>>>>>    'demote' => [
>>>>>>>>                  {
>>>>>>>>                    'rsc' => 'pgsqld:1',
>>>>>>>>                    'uname' => 'hanode1'
>>>>>>>>                  }
>>>>>>>>                ],
>>>>>>>>
>>>>>>>>    'master' => [
>>>>>>>>                  {
>>>>>>>>                    'rsc' => 'pgsqld:1',
>>>>>>>>                    'uname' => 'hanode1'
>>>>>>>>                  }
>>>>>>>>                ],
>>>>>>>>
>>>>>>>>    'promote' => [
>>>>>>>>                   {
>>>>>>>>                     'rsc' => 'pgsqld:0',
>>>>>>>>                     'uname' => 'hanode3'
>>>>>>>>                   }
>>>>>>>>                 ],
>>>>>>>>    'slave' => [
>>>>>>>>                 {
>>>>>>>>                   'rsc' => 'pgsqld:0',
>>>>>>>>                   'uname' => 'hanode3'
>>>>>>>>                 },
>>>>>>>>                 {
>>>>>>>>                   'rsc' => 'pgsqld:2',
>>>>>>>>                   'uname' => 'hanode2'
>>>>>>>>                 }
>>>>>>>>               ],
>>>>>>>>
>>>>>>>>  }
>>>>>>>>
>>>>>>>> In case this comes from our side, here is code building this:
>>>>>>>>
>>>>>>>>  https://github.com/dalibo/PAF/blob/6e86284bc647ef1e81f01f047f1862e40ba62906/lib/OCF_Functions.pm#L444
>>>>>>>>
>>>>>>>> But looking at the variable itself in debug logs, I always find it empty,
>>>>>>>> in various situations (switchover, recover, failover).
>>>>>>>>
>>>>>>>> If I understand the documentation correctly, I would expect 'active' to
>>>>>>>> list all the three resources, shouldn't it? Currently, to bypass this, we
>>>>>>>> consider: active == master + slave
>>>>>>>
>>>>>>> You're right, it should. The pacemaker code that generates the "active"
>>>>>>> variables is the same used for "demote" etc., so it seems unlikely the
>>>>>>> issue is on pacemaker's side. Especially since your code treats active
>>>>>>> etc. differently from demote etc., it seems like it must be in there
>>>>>>> somewhere, but I don't see where.
>>>>>>
>>>>>> The code treat active, inactive, start and stop all together, for any
>>>>>> cloned resource. If the resource is a multistate, it adds promote, demote,
>>>>>> slave and master.
>>>>>>
>>>>>> Note that from this piece of code, the 7 other notify vars are set
>>>>>> correctly: start, stop, inactive, promote, demote, slave, master. Only
>>>>>> active is always missing.
>>>>>>
>>>>>> I'll investigate and try to find where is hiding the bug.
>>>>>
>>>>> So I added a piece of code to dump the **all** the environment variables to
>>>>> a temp file as early as possible **to avoid any interaction with our perl
>>>>> module** in the code of the RA, ie.:
>>>>>
>>>>>  BEGIN {
>>>>>    use Time::HiRes qw(time);
>>>>>    my $now = time;
>>>>>    open my $fh, ">", "/tmp/test-$now.env.txt";
>>>>>    printf($fh "%-20s = ''%s''\n", $_, $ENV{$_}) foreach sort keys %ENV;
>>>>>  }
>>>>>
>>>>> Then I started my cluster and set maintenance-mode=false while no resources
>>>>> where running. So the debug files contains the probe action, start on all
>>>>> nodes, one promote on the master and the first monitors. The "*active"
>>>>> variables are always empty anywhere in the cluster. Find in attachment the
>>>>> result of the following command on the master node:
>>>>>
>>>>>  for i in test-*; do echo "===== $i ====="; grep OCF_ $i; done >
>>>>> debug-env.txt
>>>>>
>>>>> I'm using Pacemaker 1.1.13-10.el7_2.2-44eb2dd under CentOS 7.2.1511.
>>>>>
>>>>> For completeness, I added the Pacemaker configuration I use for my 3 node
>>>>> dev/test cluster.
>>>>>
>>>>> Let me know if you think of more investigations and test I could run on this
>>>>> issue. I'm out of ideas for tonight (and I really would prefer having this
>>>>> bug on my side).
>>>>
>>>> From your environment dumps, what I think is happening is that you are
>>>> getting multiple notifications (start, pre-promote, post-promote) in a
>>>> single cluster transition. So the variables reflect the initial state of
>>>> that transition -- none of the instances are active, all three are being
>>>> started (so the nodes are in the "*_start_*" variables), and one is
>>>> being promoted.
>>>
>>>
>>> Yes, this is what happening here. It's embarrassing I didn't thought about
>>> that :)
>>>
>>>> The starts will be done before the promote. If one of the starts fails,
>>>> the transition will be aborted, and a new one will be calculated. So, if
>>>> you get to the promote, you can assume anything in "*_start_*" is now
>>>> active.
>>>
>>> I did another simple test:
>>>
>>>  * 3 ms clones are running on hanode1 hanode2 hanode3
>>>  * master role is on hanode1
>>>  * I move the master role to hanode 2 using: 
>>>    "pcs resource move pgsql-ha hanode2 --master"
>>>
>>> The transition gives us:
>>>
>>>  * demote on hanode1
>>>  * promote en hanode2
>>>
>>> I suppose all the three clone on hanode1, hanode2 and hanode3 should appear in
>>> active env variable in this context, isn't it?
>>>
>>> Please, find in attachment the environment dumps of this transition from
>>> hanode1. You'll see both "OCF_RESKEY_CRM_meta_notify_active_resource" and
>>> "OCF_RESKEY_CRM_meta_notify_active_uname" only contains one char: a space.
>>>
>>> I start looking at the Pacemaker code, at least to have a better understanding
>>> on where environment variables are set and when they are available. I was out
>>> of luck so far but I lack of time. Any pointers would be appreciated :)
>>>
>>>>> On a side note, I noticed with these debug files that the notify
>>>>> variables where also available outside of notify actions (start and notify
>>>>> here). Are they always available during "transition actions" (start, stop,
>>>>> promote, demote)? Checking at the mysql RA, they are using
>>>>> OCF_RESKEY_CRM_meta_notify_master_uname during the start action. So I
>>>>> suppose it's safe?
>>>>
>>>> Good question, I've never tried that before. I'm reluctant to say it's
>>>> guaranteed; it's possible seeing them in the start action is a side
>>>> effect of the current implementation and could theoretically change in
>>>> the future. But if mysql is relying on it, I suppose it's
>>>> well-established already, making changing it unlikely ...
>>>
>>> Thank you very much for this clarification. Presently we keep in a private
>>> attribute what we //think// (we can not rely on active_uname :/) are the active
>>> uname for the ms resource. As it seems the notify vars appears outside of notify
>>> action is just a side effect of the current implementation, I prefer to stay
>>> away from them when we are not in a notify action and keep our current
>>> implementation.
>>>
>>> Thank you,
>>
>>
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