Kaleb S KEITHLEY 40a24f5ab9 common-ha: reliable grace using pacemaker notify actions ... Using *-dead_ip-1 resources to track on which nodes the ganesha.nfsd had died was found to be unreliable. Running `pcs status` in the ganesha_grace monitor action was seen to time out during failover; the HA devs opined that it was, generally, not a good idea to run `pcs status` in a monitor action in any event. They suggested using the notify feature, where the resources on all the nodes are notified when a clone resource agent dies. This change adds a notify action to the ganesha_grace RA. The ganesha_mon RA monitors its ganesha.nfsd daemon. While the daemon is running, it creates two attributes: ganesha-active and grace-active. When the daemon stops for any reason, the attributes are deleted. Deleting the ganesha-active attribute triggers the failover of the virtual IP (the IPaddr RA) to another node where ganesha.nfsd is still running. The ganesha_grace RA monitors the grace-active attribute. When the grace-active attibute is deleted, the ganesha_grace RA stops, and will not restart. This triggers pacemaker to trigger the notify action in the ganesha_grace RAs on the other nodes in the cluster; which send a DBUS message to their ganesha.nfsd. (N.B. grace-active is a bit of a misnomer. while the grace-active attribute exists, everything is normal and healthy. Deleting the attribute triggers putting the surviving ganesha.nfsds into GRACE.) To ensure that the remaining/surviving ganesha.nfsds are put into NFS-GRACE before the IPaddr (virtual IP) fails over there is a short delay (sleep) between deleting the grace-active attribute and the ganesha-active attribute. To summarize: 1. on node 2 ganesha_mon:monitor notices that ganesha.nfsd has died 2. on node 2 ganesha_mon:monitor deletes its grace-active attribute 3. on node 2 ganesha_grace:monitor notices that grace-active is gone and returns OCF_ERR_GENERIC, a.k.a. new error. When pacemaker tries to (re)start ganesha_grace, its start action will return OCF_NOT_RUNNING, a.k.a. known error, don't attempt further restarts. 4. on nodes 1, 3, etc., ganesha_grace:notify receives a post-stop notification indicating that node 2 is gone, and sends a DBUS message to its ganesha.nfsd putting it into NFS-GRACE. 5. on node 2 ganesha_mon:monitor waits a short period, then deletes its ganesha-active attribute. This triggers the IPaddr (virt IP) failover according to constraint location rules. ganesha_nfsd modified to run for the duration, start action is invoked to setup the /var/lib/nfs symlink, stop action is invoked to restore it. ganesha-ha.sh modified accordingly to create it as a clone resource. BUG: 1290865 Change-Id: I1ba24f38fa4338b3aeb17c65645e9f439387ff57 Signed-off-by: Kaleb S KEITHLEY <kkeithle@redhat.com> Reviewed-on: http://review.gluster.org/12964 Smoke: Gluster Build System <jenkins@build.gluster.com> NetBSD-regression: NetBSD Build System <jenkins@build.gluster.org> CentOS-regression: Gluster Build System <jenkins@build.gluster.com> Reviewed-on: http://review.gluster.org/13725		2016-03-14 21:34:27 -07:00
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ganesha-ha.md	common-ha: reliable grace using pacemaker notify actions	2016-03-14 21:34:27 -07:00