[Pacemaker] Validate strategy for RA on DRBD standby node

[David McCurley]

Pacemaker and list newbie here :)

I'm writing a resource adapter in python for the newer release of OpenLDAP but I need some pointers on a strategy for the validate function in a certain case.  (In python because the more advanced shell scripting hurts my head :).  Here is the situation:

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.

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:
----------------------------------------------
============
Last updated: Wed Feb 23 07:35:19 2011
Stack: openais
Current DC: vcoresrv1 - partition with quorum
Version: 1.0.8-042548a451fce8400660f6031f4da6f0223dd5dd
2 Nodes configured, 2 expected votes
5 Resources configured.
============

Online: [ vcoresrv1 vcoresrv2 ]

fs_vcoreshare   (ocf::heartbeat:Filesystem):    Started vcoresrv1
 Master/Slave Set: ms_drbd_vcoreshare
     Masters: [ vcoresrv1 ]
     Slaves: [ vcoresrv2 ]
clusterip       (ocf::heartbeat:IPaddr2):       Started vcoresrv1
clusteripsourcing       (ocf::heartbeat:IPsrcaddr):     Started vcoresrv1

Failed actions:
    ldap_monitor_0 (node=vcoresrv2, call=130, rc=5, status=complete): not installed
---------------------------------------------

Is there a way for my RA to know that it is being called on the active node instead of the passive node.  Or more generally, what would anyone recommend here?  I really didn't want to write the resource adapter so it would be specific to our setup (e.g. checking to make sure the DRBD mount is readable before looking for the config files).  Maybe Pacemaker passes in some extra env variable that can be used?

I'm reluctanct to post the code for the RA here in the list because it is 450 lines.  But, here is the logic for the validate function:

if the appropriate slapd user and group do not exist:
   return OCF_ERR_INSTALLED
if the ldap config file doesn't exist or isn't readable by the slapd user:
   return OCF_ERR_INSTALLED
if the ldap binary doesn't exist or isn't executable:
   return OCF_ERR_INSTALLED
return OCF_SUCCESS

Or maybe I'm overdoing it in my tests or have misinterpreted the "OCF Resource Agent Developer's Guide"?

Any advice or guidance / clarification appreciated.

Thanks,

Mac