[Pacemaker] [Problem or Enhancement]When attrd reboots, a fail count is initialized.

[renayama19661014 at ybb.ne.jp]

Hi Andrew,

I registered these contents with Bugzilla as enhancement of the functions.

 * http://developerbugs.linux-foundation.org/show_bug.cgi?id=2501

Thanks,
Hideo Yamauchi.


--- renayama19661014 at ybb.ne.jp wrote:

> Hi Andrew,
> 
> Thank you for comment.
> 
> > > Is the change of this attrd and crmd difficult?
> > 
> > I dont think so.
> > But its not a huge priority because I've never heard of attrd actually crashing.
> > 
> > So while I agree that its theoretically a problem, in practice no-one
> > is going to hit this in production.
> > Even if they were unlucky enough to see it, at worst the resource is
> > able to run on the node again - which doesn't seem that bad for a HA
> > cluster :-)
> 
> 
> All right.
> 
> I register this problem with Bugzilla as a demand first of all. 
> I will wait for the opinion from other users already appearing a little.
> 
> Thanks,
> Hideo Yamauchi.
> 
> --- Andrew Beekhof <andrew at beekhof.net> wrote:
> 
> > On Fri, Oct 1, 2010 at 4:00 AM,  <renayama19661014 at ybb.ne.jp> wrote:
> > > Hi Andrew,
> > >
> > > Thank you for comment.
> > >
> > >> During crmd startup, one could read all the values from attrd into the
> > >> hashtable.
> > >> So the hashtable would only do something if only attrd went down.
> > >
> > > If attrd communicates with crmd at the time of start and reads the data of the hash table,
> the
> > problem
> > > seems to be able to be settled.
> > >
> > > Is the change of this attrd and crmd difficult?
> > 
> > I dont think so.
> > But its not a huge priority because I've never heard of attrd actually crashing.
> > 
> > So while I agree that its theoretically a problem, in practice no-one
> > is going to hit this in production.
> > Even if they were unlucky enough to see it, at worst the resource is
> > able to run on the node again - which doesn't seem that bad for a HA
> > cluster :-)
> > 
> > >
> > >
> > >> I mean: did you see this behavior in a production system, or only
> > >> during testing when you manually killed attrd?
> > >
> > > We carry out kill-command by manual operation as one of the tests of the trouble of the
> > processes.
> > > Our user minds behavior of the process trouble very much.
> > >
> > > Best Regards,
> > > Hideo Yamauchi.
> > >
> > > --- Andrew Beekhof <andrew at beekhof.net> wrote:
> > >
> > >> On Wed, Sep 29, 2010 at 3:59 AM,  <renayama19661014 at ybb.ne.jp> wrote:
> > >> > Hi Andrew,
> > >> >
> > >> > Thank you for comment.
> > >> >
> > >> >> The problem here is that attrd is supposed to be the authoritative
> > >> >> source for this sort of data.
> > >> >
> > >> > Yes. I understand.
> > >> >
> > >> >> Additionally, you don't always want attrd reading from the status
> > >> >> section - like after the cluster restarts.
> > >> >
> > >> > The problem seems to be able to solve even that it retrieves a status section from cib
> > after
> > >> attrd
> > >> > rebooted.
> > >> > "method2" which I suggested is such a meaning.
> > >> >> > method 2)When attrd started, Attrd communicates with cib and receives fail-count.
> > >> >
> > >> >> For failcount, the crmd could keep a hashtable of the current values
> > >> >> which it could re-send to attrd if it detects a disconnection.
> > >> >> But that might not be a generic-enough solution.
> > >> >
> > >> > If a Hash table of crmd can maintain it, it may be a good thought.
> > >> > However, I have a feeling that the same problem happens when crmd causes trouble and
> > rebooted.
> > >>
> > >> During crmd startup, one could read all the values from attrd into the
> > >> hashtable.
> > >> So the hashtable would only do something if only attrd went down.
> > >>
> > >> >
> > >> >> The chance that attrd dies _and_ there were relevant values for
> > >> >> fail-count is pretty remote though... is this a real problem you've
> > >> >> experienced or a theoretical one?
> > >> >
> > >> > I did not understand meanings well.
> > >> > Does this mean that there is fail-count of attrd in the other node?
> > >>
> > >> I mean: did you see this behavior in a production system, or only
> > >> during testing when you manually killed attrd?
> > >>
> > >> >
> > >> > Best Regards,
> > >> > Hideo Yamauchi.
> > >> >
> > >> > --- Andrew Beekhof <andrew at beekhof.net> wrote:
> > >> >
> > >> >> On Mon, Sep 27, 2010 at 7:26 AM, �<renayama19661014 at ybb.ne.jp> wrote:
> > >> >> > Hi,
> > >> >> >
> > >> >> > When I investigated another problem, I discovered this phenomenon.
> > >> >> > If attrd causes process trouble and does not restart, the problem does not occur.
> > >> >> >
> > >> >> > Step1) After start, it causes a monitor error in UmIPaddr twice.
> > >> >> >
> > >> >> > Online: [ srv01 srv02 ]
> > >> >> >
> > >> >> > �Resource Group: UMgroup01
> > >> >> > � � UmVIPcheck (ocf::heartbeat:Dummy): Started srv01
> > >> >> > � � UmIPaddr � (ocf::heartbeat:Dummy2): � �
> �
> > >> > �Started srv01
> > >> >> >
> > >> >> > Migration summary:
> > >> >> > * Node srv02:
> > >> >> > * Node srv01:
> > >> >> > � UmIPaddr: migration-threshold=10 fail-count=2
> > >> >> >
> > >> >> > Step2) Kill Attrd and Attrd reboots.
> > >> >> >
> > >> >> > Online: [ srv01 srv02 ]
> > >> >> >
> > >> >> > �Resource Group: UMgroup01
> > >> >> > � � UmVIPcheck (ocf::heartbeat:Dummy): Started srv01
> > >> >> > � � UmIPaddr � (ocf::heartbeat:Dummy2): � �
> �
> > >> > �Started srv01
> > >> >> >
> > >> >> > Migration summary:
> > >> >> > * Node srv02:
> > >> >> > * Node srv01:
> > >> >> > � UmIPaddr: migration-threshold=10 fail-count=2
> > >> >> >
> > >> >> > Step3) It causes a monitor error in UmIPaddr.
> > >> >> >
> > >> >> > Online: [ srv01 srv02 ]
> > >> >> >
> > >> >> > �Resource Group: UMgroup01
> > >> >> > � � UmVIPcheck (ocf::heartbeat:Dummy): Started srv01
> > >> >> > � � UmIPaddr � (ocf::heartbeat:Dummy2): � �
> �
> > >> > �Started srv01
> > >> >> >
> > >> >> > Migration summary:
> > >> >> > * Node srv02:
> > >> >> > * Node srv01:
> > >> >> > � UmIPaddr: migration-threshold=10 fail-count=1 -----> Fail-count return to the
> > >> first.
> > >> >> >
> > >> >> > The problem is so that attrd disappears fail-count by reboot.(Hash-tables is Lost.)
> > >> >> > It is a problem very much that the trouble number of times is initialized.
> > >> >> >
> > >> >> > I think that there is the following method.
> > >> >> >
> > >> >> > method 1)Attrd maintain fail-count as a file in "/var/run" directories and refer.
> > >> >> >
> > >> >> > method 2)When attrd started, Attrd communicates with cib and receives fail-count.
> > >> >> >
> > >> >> > Is there a better method?
> > >> >> >
> > >> >> > Please think about the solution of this problem.
> > >> >>
> > >> >> Hmmmm... a tricky one.
> > >> >>
> > >> >> The problem here is that attrd is supposed to be the authoritative
> > >> >> source for this sort of data.
> > >> >> Additionally, you don't always want attrd reading from the status
> > >> >> section - like after the cluster restarts.
> > >> >>
> > >> >> For failcount, the crmd could keep a hashtable of the current values
> > >> >> which it could re-send to attrd if it detects a disconnection.
> > >> >> But that might not be a generic-enough solution.
> > >> >>
> > >> >> The chance that attrd dies _and_ there were relevant values for
> > >> >> fail-count is pretty remote though... is this a real problem you've
> > >> >> experienced or a theoretical one?
> > >> >>
> > >> >> _______________________________________________
> > >> >> Pacemaker mailing list: Pacemaker at oss.clusterlabs.org
> > >> >> http://oss.clusterlabs.org/mailman/listinfo/pacemaker
> > >> >>
> > >> >> Project Home: http://www.clusterlabs.org
> > >> >> Getting started: http://www.clusterlabs.org/doc/Cluster_from_Scratch.pdf
> > >> >> Bugs: http://developerbugs.linux-foundation.org/enter_bug.cgi?product=Pacemaker
> 
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