[ClusterLabs] Notification agent and Notification recipients

[Ken Gaillot]

On Thu, 2017-08-03 at 12:31 +0530, Sriram wrote:
> 
> Hi Team,
> 
> 
> We have a four node cluster (1 active : 3 standby) in our lab for a
> particular service. If the active node goes down, one of the three
> standby node  becomes active. Now there will be (1 active :  2
> standby : 1 offline).
> 
> 
> Is there any way where this newly elected node sends notification to
> the remaining 2 standby nodes about its new status ?

Hi Sriram,

This depends on how your service is configured in the cluster.

If you have a clone or master/slave resource, then clone notifications
is probably what you want (not alerts, which is the path you were going
down -- alerts are designed to e.g. email a system administrator after
an important event).

For details about clone notifications, see:

http://clusterlabs.org/doc/en-US/Pacemaker/1.1-pcs/html-single/Pacemaker_Explained/index.html#_clone_resource_agent_requirements

The RA must support the "notify" action, which will be called when a
clone instance is started or stopped. See the similar section later for
master/slave resources for additional information. See the mysql or
pgsql resource agents for examples of notify implementations.

> I was exploring "notification agent" and "notification recipient"
> features, but that doesn't seem to work. /etc/sysconfig/notify.sh
> doesn't get invoked even in the newly elected active node. 

Yep, that's something different altogether -- it's only enabled on RHEL
systems, and solely for backward compatibility with an early
implementation of the alerts interface. The new alerts interface is more
flexible, but it's not designed to send information between cluster
nodes -- it's designed to send information to something external to the
cluster, such as a human, or an SNMP server, or a monitoring system.


> Cluster Properties:
>  cluster-infrastructure: corosync
>  dc-version: 1.1.17-e2e6cdce80
>  default-action-timeout: 240
>  have-watchdog: false
>  no-quorum-policy: ignore
>  notification-agent: /etc/sysconfig/notify.sh
>  notification-recipient: /var/log/notify.log
>  placement-strategy: balanced
>  stonith-enabled: false
>  symmetric-cluster: false
> 
> 
> 
> 
> I m using the following versions of pacemaker and corosync.
> 
> 
> /usr/sbin # ./pacemakerd --version
> Pacemaker 1.1.17
> Written by Andrew Beekhof
> /usr/sbin # ./corosync -v
> Corosync Cluster Engine, version '2.3.5'
> Copyright (c) 2006-2009 Red Hat, Inc.
> 
> 
> Can you please suggest if I m doing anything wrong or if there any
> other mechanisms to achieve this ?
> 
> 
> Regards,
> Sriram.
> 
> 
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-- 
Ken Gaillot <kgaillot at redhat.com>