How to Set up Nginx High Availability with Pacemaker and Corosync

Prerequisites

• 2 or more CentOS 7 Serverpre
  • web01       10.0.15.10
  • web02       10.0.15.11
  • web03       10.0.15.12
• Floating IP Address 10.0.15.15
• Root Privileges

What we will do:

1. Map the Host File
2. Install Epel Repository and Nginx
3. Install and Configure Pacemaker, Corosync, and Pcsd
4. Create and Configure the Cluster
5. Disable STONITH and Ignore the Quorum Policy
6. Add the Floating-IP and Resources
7. Add Rules to the Cluster
8. Configure Firewalld
9. Test the setup

Update Host files in all servers

vim /etc/hosts

Paste the following configuration there.

10.0.15.10      web01
10.0.15.11      web02
10.0.15.12      web03

Install Epel Repository ,Nginx and pacemaker

yum -y install epel-release
yum -y install nginx
yum -y install corosync pacemaker pcs

systemctl enable pcsd
systemctl enable corosync
systemctl enable pacemaker

systemctl start pcsd

Change hacluster user password

passwd hacluster

Create and Configure the Cluster

pcs cluster auth web01 web02 web03
Username: hacluster
Password: aqwe123@

Now it’s time set up the cluster. Define the cluster name and all servers that will be part of the cluster.

pcs cluster setup --name hakase_cluster web01 web02 web03

Now start all cluster services and also enable them.

pcs cluster start --all
pcs cluster enable --all
pcs status cluster

Disable STONITH and Ignore the Quorum Policy

pcs property set stonith-enabled=false
pcs property set no-quorum-policy=ignore
pcs property list

Add the Floating-IP and Resources

pcs resource create virtual_ip ocf:heartbeat:IPaddr2 ip=10.0.15.15 cidr_netmask=32 op monitor interval=30s

If you want, add a new resource for the Nginx ‘webserver’.

pcs resource create webserver ocf:heartbeat:nginx configfile=/etc/nginx/nginx.conf op monitor timeout="5s" interval="5s"
pcs status resources

Add Constraint Rules to the Cluster
In this step, we will setup High Availability Rules, and will setup resource constraint with the pcs command line interface.

Set the collation constraint for webserver and virtual_ip resources with score ‘INFINITY’. Also, setup the webserver and virtual_ip resources as same on all server nodes.

pcs constraint colocation add webserver virtual_ip INFINITY

Set the ‘virtual_ip’ and ‘webserver’ resources always on same node servers.

pcs constraint order virtual_ip then the webserver

Next, stop the cluster and then start again.

pcs cluster stop --all
pcs cluster start --all

Now, check again the resources and you will see their status as ‘Started’ on the same server ‘web01’.

pcs status resources

virtual_ip and webserver resources have been started on the same server/node ‘web01’.

Configure Firewalld
The HA-Cluster will run under the firewall configuration firewalld – install it if you do not have the package.

yum -y install firewalld

Start firewalld and enable it to run automatically every time at system boot using following systemctl commands.

systemctl start firewalld
systemctl enable firewalld

Next, add new services to the firewalld with firewall-cmd commands – add high-availability service, HTTP, and HTTPS services for Nginx.

firewall-cmd --permanent --add-service=high-availability
firewall-cmd --permanent --add-service=http
firewall-cmd --permanent --add-service=https

Reload the firewall configuration, and check all services.

firewall-cmd --reload
firewall-cmd --list-all

Make sure ha service with HTTP and https is there on the list.
Testing
In this step, we’re gonna do some test for the cluster. Test the node status (‘Online’ or ‘Offline’), test the corosync members and status, and then test the high-availability of the Nginx webserver by accessing the Floating IP address.

Test node status with the following command.

pcs status nodes

All nodes are up ‘Online’.

Test the corosync members.

corosync-cmapctl | grep members

You will get Corosync members IP address.

Check the Corosync members, and you will see the result as shown below.

pcs status corosync

And lastly, check the webserver High Availability. Open your web browser and type the Floating IP address ‘10.0.15.15’.

You will see the web page from the ‘web01’ server.
Next, stop the cluster on the ‘web01’ server with the command below.

pcs cluster stop web01

And check again the page, and you will get the page from the ‘web02’ server as below.

Additional:

Check the cluster status with the command below.

pcs status

And you will get the result as shown below.

Setup of Nginx webserver High Availability with Pacemaker, Corosync, and Pcsd on CentOS 7 server has been completed successfully.