Corosync<\/strong> Cluster Engine is an open source project derived from the OpenAIS project under new BSD License. It’s a group communication system with additional features for implementing High Availability within applications.<\/p>\n There are some applications for the Pacemaker interfaces. Pcsd<\/strong> is one of the Pacemaker command line interface and GUI for managing the Pacemaker. We can create, configure, or add a new node to the cluster with the pcsd command pcs.<\/p>\n Prerequisites<\/strong><\/p>\n What we will do:<\/strong><\/p>\n Note<\/strong>:\u00a0Run step 1 – 3 on all servers web01, web02 and web03.<\/p>\n The first step we must do is to\u00a0edit the host file on each server in order to map the hostname of all servers. We’ve ‘web01’, ‘web02’ and ‘web03’ servers, login to the each server with the ssh account.<\/p>\n ssh [email\u00a0protected]<\/a>[01,02,03]\n Edit the ‘\/etc\/hosts’ file with vim<\/a>.<\/p>\n vim \/etc\/hosts<\/p>\n Paste the following configuration there.<\/p>\n Save and exit.<\/p>\n Now test the hosts’ mapping configuration.<\/p>\n ping -c 3 web01 Make sure ‘web01’, ‘web02’ and ‘web03’ are\u00a0mapped to correct IP addresses.<\/p>\n In this step, we will install the epel repository and then install the Nginx web server. EPEL or Extra Packages for Enterprise Linux repository is needed for installing Nginx packages.<\/p>\n Install EPEL Repository using the following\u00a0yum command.<\/p>\n yum -y install epel-release<\/p>\n Now install Nginx web server from the EPEL repository.<\/p>\n yum -y install nginx<\/p>\n After\u00a0the installation is complete, change the default index.html page on each server with a new page.<\/p>\n #Run Command on ‘web01’ #Run Command on ‘web02’ #Run Command on ‘web03’ EPEL Repository and Nginx web server are now installed on the system.<\/p>\n Pacemaker, Corosync, and Pcsd are available in\u00a0the default system repository. So they\u00a0all can be installed from the CentOS repository using the following\u00a0yum command.<\/p>\n yum -y install corosync pacemaker pcs<\/p>\n After\u00a0the installation has been completed, enable all services to launch automatically at system boot\u00a0using the systemctl commands below.<\/p>\n systemctl enable pcsd Now start the pcsd Pacemaker command line interface on all servers.<\/p>\n systemctl start pcsd<\/p>\n Next, create a new password for ‘hacluster’ user and use the same password for all servers. This user has been created automatically during software installation.<\/p>\n Here’s how you configure a password for the ‘hacluster<\/strong>‘ user.<\/p>\n passwd hacluster High Availability software stack Pacemaker, Corosync, and Pcsd are installed on to the system.<\/p>\n Note<\/strong>: Run steps 4 – 7 on ‘web01’<\/strong> only.<\/p>\n In this step, we will create a new cluster with 3 centos servers. Then configure\u00a0the Floating IP address and add\u00a0new Nginx resources.<\/p>\n To create the cluster, we need to authorize all servers using the pcs command and the hacluster user.<\/p>\n Authorize all servers with the pcs command and hacluster user and password.<\/p>\n pcs cluster auth web01 web02 web03 Now it’s time set up the cluster. Define the cluster name and all servers that will be part of the cluster.<\/p>\n pcs cluster setup –name hakase_cluster web01 web02 web03<\/p>\n Now start all cluster services and also enable them.<\/p>\n pcs cluster start –all Next, check the cluster status.<\/p>\n pcs status cluster<\/p>\n Since we’re not using the fencing device, we will disable the STONITH. STONITH or Shoot The Other Node In The Head is the fencing implementation on Pacemaker. If you’re in production, it’s better to enable STONITH.<\/p>\n Disable STONITH with the following pcs command.<\/p>\n pcs property set stonith-enabled=false<\/p>\n Next, for the Quorum policy, ignore it.<\/p>\n pcs property set no-quorum-policy=ignore<\/p>\n Check the property list and make sure stonith and the quorum policy are disabled.<\/p>\n pcs property list<\/p>\n The STONITH and Quorum Policy is disabled.<\/p>\n Floating IP is the IP address that can be migrated\/moved automatically from one server to another server in\u00a0the same Data Center. And we’ve already defined the floating IP address for the Pacemaker High-Availability to be ‘10.0.15.15’. Now we want to add two resources, the Floating IP address resource with the name ‘virtual_ip’ and a new resource for the Nginx web server named ‘webserver’.<\/p>\n Add the new resource floating IP address ‘virtual_ip’ using the\u00a0pcs command as shown below.<\/p>\n pcs resource create virtual_ip ocf:heartbeat:IPaddr2 ip=10.0.15.15 cidr_netmask=32 op monitor interval=30s<\/p>\n Next, add a new resource for the Nginx ‘webserver’.<\/p>\n pcs resource create webserver ocf:heartbeat:nginx configfile=\/etc\/nginx\/nginx.conf op monitor timeout=”5s” interval=”5s”<\/p>\n Make sure you got no error result, then check the resources available.<\/p>\n pcs status resources<\/p>\n You will see two resources ‘virtual_ip’ and a ‘webserver’. New resources for the Floating IP and Nginx web server have been added.<\/p>\n In this step, we will setup High Availability Rules, and will setup resource constraint with the pcs command line interface.<\/p>\n Set the collation constraint for webserver and virtual_ip resources with score ‘INFINITY’. Also, setup the webserver and virtual_ip resources as\u00a0same on all server nodes.<\/p>\n pcs constraint colocation add webserver virtual_ip INFINITY<\/p>\n Set the ‘virtual_ip’ and ‘webserver’ resources always on same node servers.<\/p>\n pcs constraint order virtual_ip then the webserver<\/p>\n Next, stop the cluster and then start again.<\/p>\n pcs cluster stop –all Now, check again the resources and you will see their\u00a0status as\u00a0‘Started’ on the same server ‘web01’.<\/p>\n pcs status resources<\/p>\n virtual_ip and webserver resources have been started on the same server\/node ‘web01’.<\/p>\n The HA-Cluster will run under the firewall configuration firewalld – install it if you do not have the package.<\/p>\n yum -y install firewalld<\/p>\n Start firewalld and enable\u00a0it to run automatically every time at system boot\u00a0using following systemctl commands.<\/p>\n systemctl start firewalld Next, add new services to the firewalld with firewall-cmd commands – add high-availability service, HTTP, and HTTPS services for Nginx.<\/p>\n firewall-cmd –permanent –add-service=high-availability Reload the firewall configuration, and check all services.<\/p>\n firewall-cmd –reload Make sure ha service with HTTP and https is there on the list.<\/p>\n 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.<\/p>\n Test node status with the following command.<\/p>\n pcs status nodes<\/p>\n All nodes are up ‘Online’.<\/p>\n Test the corosync members.<\/p>\n corosync-cmapctl | grep members<\/p>\n You will get Corosync members IP address.<\/p>\n Check the Corosync members, and you will see the result as shown below.<\/p>\n pcs status corosync<\/p>\n And lastly, check the webserver High Availability. Open your web browser and type the Floating IP address ‘10.0.15.15’.<\/p>\n You will see the web page from the ‘web01’ server.<\/p>\n Next, stop the cluster on the ‘web01’ server with the command below.<\/p>\n pcs cluster stop web01<\/p>\n And check again the page, and you will get the page from the ‘web02’ server as below.<\/p>\n\n
\n
\n
Step 1 – Map the Host File<\/h2>\n
10.0.15.10\u00a0\u00a0\u00a0\u00a0\u00a0 web01
ping -c 3 web02
ping -c 3 web03<\/p>\n![\"Check](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7.png\" "\\"\\"")
<\/a><\/p>\nStep 2 – Install Epel Repository and Nginx<\/h2>\n
echo ‘<h1>web01 – hakase-labs<\/h1>’ > \/usr\/share\/nginx\/html\/index.html<\/p>\n
echo ‘<h1>web02 – hakase-labs<\/h1>’ > \/usr\/share\/nginx\/html\/index.html<\/p>\n
echo ‘<h1>web03 – hakase-labs<\/h1>’ > \/usr\/share\/nginx\/html\/index.html<\/p>\n![\"Install](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-1.png\" "\\"\\"")
<\/a><\/p>\nStep 3 – Install and configure Pacemaker, Corosync, and Pcsd<\/h2>\n
systemctl enable corosync
systemctl enable pacemaker<\/p>\n
Enter new password:<\/p>\n![\"Install](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-2.png\" "\\"\\"")
<\/a><\/p>\nStep 4 – Create and Configure the Cluster<\/h2>\n
Username: hacluster
Password: [email\u00a0protected]<\/a><\/p>\n![\"Create](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-3.png\" "\\"\\"")
<\/a><\/p>\n
pcs cluster enable –all<\/p>\n![\"Start](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-4.png\" "\\"\\"")
<\/a><\/p>\n![\"Check](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-5.png\" "\\"\\"")
<\/a><\/p>\nStep 5 – Disable STONITH and Ignore the Quorum Policy<\/h2>\n
![\"Disable](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-6.png\" "\\"\\"")
<\/a><\/p>\nStep 6 – Add the Floating-IP and Resources<\/h2>\n
![\"Add](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-7.png\" "\\"\\"")
<\/a><\/p>\nStep 7 – Add Constraint Rules to the Cluster<\/h2>\n
pcs cluster start –all<\/p>\n![\"Add](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-8.png\" "\\"\\"")
<\/a><\/p>\n![\"Check](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-9.png\" "\\"\\"")
<\/a><\/p>\nStep 8 – Configure Firewalld<\/h2>\n
systemctl enable firewalld<\/p>\n
firewall-cmd –permanent –add-service=http
firewall-cmd –permanent –add-service=https<\/p>\n![\"Configure](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-10.png\" "\\"\\"")
<\/a><\/p>\n
firewall-cmd –list-all<\/p>\n![\"Reload](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-11.png\" "\\"\\"")
<\/a><\/p>\nStep 9 – Testing<\/h2>\n
![\"Testing](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-12.png\" "\\"\\"")
<\/a><\/p>\n![\"Corosync](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-13.png\" "\\"\\"")
<\/a><\/p>\n![\"Corosync](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-14.png\" "\\"\\"")
<\/a><\/p>\n![\"Website](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-15.png\" "\\"\\"")
<\/a><\/p>\n
![\"website](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-16.png\" "\\"\\"")
<\/a><\/p>\n![\"Check](\"https:\/\/afaghhosting.net\/blog\/wp-content\/uploads\/2017\/12\/how-to-set-up-nginx-high-availability-with-pacemaker-and-corosync-on-centos-7-17.png\" "\\"\\"")
<\/a><\/p>\n