Would it be appropriate to post the first result of coding here for review and recommendations?
If so, just post code in-line or as an attachment? If not, no problemo. ----- Original Message ----- > From: "Dejan Muhamedagic" <deja...@fastmail.fm> > To: "The Pacemaker cluster resource manager" <pacemaker@oss.clusterlabs.org> > Sent: Friday, February 25, 2011 10:53:34 AM > Subject: Re: [Pacemaker] Validate strategy for RA on DRBD standby node > On Thu, Feb 24, 2011 at 10:49:27AM -0500, David McCurley wrote: > > Thanks for the quick reply and especially the link. It was much > > better and more thorough in testing than the other shell ra ldap > > link I found. > > > > > That would be the first python RA. BTW, there was recently posted > > > slapd RA (implemented in shell), which I should review, but > > > haven't done that yet. /At any rate, that RA does not support > > > multi-state resources which I think would be essential. Did you > > > plan to do that? At any rate, I'd suggest that you check that > > > code too and then see if you need to do your own implementation. > > > The thread starts here: > > > > > > http://marc.info/?l=linux-ha-dev&m=129666245428850&w=2 > > > > Great stuff and very thorough. But it doesn't look like it will work > > in our config because the files won't exist on the DRBD slave. I > > will use this as my new example. > > > > I'm not sure what you are referring to with "multi-state" resources. > > Is this in relation to "promote,demote, migrate_to, migrate_from" in > > the guide, i.e. master vs slave or is there more to it? I plan to > > support a master and slave later on down the road -- under pressure > > to get this rolled out now. Is there a good discussion / resource > > other than the dev guide? I had planned to try to wade through the > > DRBD RA scripts to figure it out. > > migrate_to/from are for something else. It's just promote > (slave->master) and demote (master->slave). > > > Why python? Because shell is harder for me to read and I have to > > make a good clear verbose example for some others who will also be > > doing some RA's (in python) for our custom apps. > > No problem with python. Actually, there was an idea to provide a > python class (RA or so) which would make implementing resource > agents easier. > > > > > The config file for OpenLDAP is stored in > > > > /etc/ldap/slapd.d/cn=config.ldif. This is on a DRBD > > > > active-passive system and the /etc/ldap directory is actually a > > > > symlink to the DRBD controlled share /vcoreshare/etc/ldap. The > > > > real config file is at > > > > /vcoreshare/etc/ldap/slapd.d/cn=config.ldif. > > > > > > What about the old style configuration? I assume that there are > > > still quite a few installations/distributions using those. > > > > Yes, I have some code for that, using the example slapd init script > > and the other examples I found, but no test environment for that. > > IIRC, the old configuration style is quite easy to parse. > > > > > So I'm trying to be very judicious with every function and > > > > validation, checking file permissions, etc. But the problem is > > > > that /etc/ldap/slapd.d/cn=config.ldif is only present on the > > > > active DRBD node. My validate function checks that the file is > > > > readable by the user/group that slapd is to run as. Now, as soon > > > > as I start ldap in the cluster, it starts fine, but validate > > > > fails > > > > on the standby node (because the DRBD volume isn't mounted) and > > > > crm_mon shows a failed action: > > > > > > On probes (monitor with interval 0), some parts of validation > > > which concern the local node and not the configuration should say > > > OCF_NOT_RUNNING instead of error. This is exactly that case. No > > > worries, because if the next action is start validation is > > > invoked again. Probes are issued by pacemaker to establish if the > > > resource is running and normally it is expected to be not running > > > (for instance on node startup). > > > > Ah! I have a function that checks for probes but wasn't using it > > because I didn't quite understand the semantics. > > OK, hope that it's clear now. > > Thanks, > > Dejan > > > > > Very helpful stuff, thanks! > > > > _______________________________________________ > > Pacemaker mailing list: Pacemaker@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 > > _______________________________________________ > Pacemaker mailing list: Pacemaker@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 _______________________________________________ Pacemaker mailing list: Pacemaker@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
