[ClusterLabs] Issue in resource constraints and fencing - RHEL7 - AWS EC2

[Pratip Ghosh]

Hi All,

I am implementing 2 node RedHat (RHEL 7.2) HA cluster on Amazon EC2 
instance. For floating IP I am using a shell script provided by AWS so 
that virtual IP float to another instance if any one server failed with 
health check. In basic level cluster is working but I have 2 issues on 
that which I describe in bellow.

ISSUE 1
=====
Now I need to configure fencing/STONITH to avoid split brain scenario in 
storage cluster. I want to use multi-primari (Active/Active) DRBD in my 
cluster for distributed storage. Is it possible to configure power 
fencing on AWS EC2 instance? Can any one please guide me on this?


ISSUE2
=====
Currently I am using single  primary DRBD distributed storage. I added 
cluster resources so that if any cluster node goes down then another 
cluster node will promoted DRBD volume as primary and mount it on 
/var/www/html.

This configuration is working but for only if cluster node1 goes down. 
If cluster node2 goes down all cluster resources fails over towards 
cluster node1 but whenever cluster node2 again become on-line then 
virtual_ip (cluster ip) ownership automatically goes towards cluster 
node2 again. All the remaining resources not failed over like that. In 
that case secondary IP stays with Node1 and ownership goes to Node2.

I think this is an issue with resource stickiness or resource constraint 
but here I am totally clueless. Can any one please help me on this?


My cluster details:
===========

[root at drbd01 ~]# pcs config
Cluster Name: web_cluster
Corosync Nodes:
  ec2-52-24-8-124.us-west-2.compute.amazonaws.com 
ec2-52-27-70-12.us-west-2.compute.amazonaws.com
Pacemaker Nodes:
  ec2-52-24-8-124.us-west-2.compute.amazonaws.com 
ec2-52-27-70-12.us-west-2.compute.amazonaws.com

Resources:
  Resource: virtual_ip (class=ocf provider=heartbeat type=IPaddr2)
   Attributes: ip=10.98.70.100 cidr_netmask=24
   Operations: start interval=0s timeout=20s (virtual_ip-start-interval-0s)
               stop interval=0s timeout=20s (virtual_ip-stop-interval-0s)
               monitor interval=30s (virtual_ip-monitor-interval-30s)
  Resource: WebSite (class=ocf provider=heartbeat type=apache)
   Attributes: configfile=/etc/httpd/conf/httpd.conf 
statusurl=http://10.98.70.100/server-status
   Operations: start interval=0s timeout=40s (WebSite-start-interval-0s)
               stop interval=0s timeout=60s (WebSite-stop-interval-0s)
               monitor interval=1min (WebSite-monitor-interval-1min)
  Master: WebDataClone
   Meta Attrs: master-max=1 master-node-max=1 clone-max=2 
clone-node-max=1 notify=true
   Resource: WebData (class=ocf provider=linbit type=drbd)
    Attributes: drbd_resource=r1
    Operations: start interval=0s timeout=240 (WebData-start-interval-0s)
                promote interval=0s timeout=90 
(WebData-promote-interval-0s)
                demote interval=0s timeout=90 (WebData-demote-interval-0s)
                stop interval=0s timeout=100 (WebData-stop-interval-0s)
                monitor interval=60s (WebData-monitor-interval-60s)
  Resource: WebFS (class=ocf provider=heartbeat type=Filesystem)
   Attributes: device=/dev/drbd1 directory=/var/www/html fstype=xfs
   Operations: start interval=0s timeout=60 (WebFS-start-interval-0s)
               stop interval=0s timeout=60 (WebFS-stop-interval-0s)
               monitor interval=20 timeout=40 (WebFS-monitor-interval-20)

Stonith Devices:
Fencing Levels:

Location Constraints:
Ordering Constraints:
   promote WebDataClone then start WebFS (kind:Mandatory) 
(id:order-WebDataClone-WebFS-mandatory)
   start WebFS then start virtual_ip (kind:Mandatory) 
(id:order-WebFS-virtual_ip-mandatory)
   start virtual_ip then start WebSite (kind:Mandatory) 
(id:order-virtual_ip-WebSite-mandatory)
Colocation Constraints:
   WebSite with virtual_ip (score:INFINITY) 
(id:colocation-WebSite-virtual_ip-INFINITY)
   WebFS with WebDataClone (score:INFINITY) (with-rsc-role:Master) 
(id:colocation-WebFS-WebDataClone-INFINITY)
   WebSite with WebFS (score:INFINITY) 
(id:colocation-WebSite-WebFS-INFINITY)

Resources Defaults:
  resource-stickiness: INFINITY
Operations Defaults:
  timeout: 240s

Cluster Properties:
  cluster-infrastructure: corosync
  cluster-name: web_cluster
  dc-version: 1.1.13-10.el7-44eb2dd
  default-resource-stickiness: INFINITY
  have-watchdog: false
  no-quorum-policy: ignore
  stonith-action: poweroff
  stonith-enabled: false



Regards,
Pratip Ghosh.

-- 
Thanks,

Pratip.
+91-9007515795

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