How to set up Apache HTTPD active-active with PCS

An active-active Apache HTTPD cluster runs the web service on multiple nodes at the same time so traffic can be shared and a single node outage does not take the site offline.

A Pacemaker + Corosync cluster managed with the pcs CLI can control Apache HTTPD as a systemd resource and clone it so one instance runs per node. The cluster continuously monitors each instance and recovers failed services, while routing is handled separately by a load balancer or DNS.

Configuration files, enabled modules, and web content must match on every node because requests can land on any server at any time. Disable standalone service enablement so systemd does not start Apache HTTPD outside of cluster control, and plan session storage, TLS termination, and health checks before distributing production traffic.

Related: How to plan active-active high availability with Pacemaker
Related: How to set up Apache HTTPD high availability with PCS

Steps to set up Apache HTTPD active-active with PCS:

  1. Confirm the cluster is online and has quorum. 
    $ sudo pcs status
Cluster name: clustername
Cluster Summary:
  * Stack: corosync (Pacemaker is running)
  * Current DC: node-01 (version 2.1.6-6fdc9deea29) - partition with quorum
  * Last updated: Thu Jan  1 00:49:38 2026 on node-01
##### snipped #####

    Related: How to check Pacemaker cluster status

  2. Identify the Apache HTTPD service unit name. 
    $ systemctl list-unit-files --type=service | grep -E '^(apache2|httpd)\.service'
apache2.service                              disabled        enabled

    The unit name is referenced in pcs as systemd:httpd or systemd:apache2.

    Related: How to manage Pacemaker cluster services with systemctl in Linux

  3. Validate the Apache HTTPD configuration on each cluster node. 
    $ sudo apachectl configtest
Syntax OK

    Use apache2ctl configtest when apachectl is not present.

    Related: How to test Apache configuration

  4. Disable the standalone Apache HTTPD service in systemd. 
    $ sudo systemctl disable --now apache2
Synchronizing state of apache2.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install disable apache2
Synchronizing state of apache2.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install disable apache2
Synchronizing state of apache2.service with SysV service script with /usr/lib/systemd/systemd-sysv-install.
Executing: /usr/lib/systemd/systemd-sysv-install disable apache2

    Apache HTTPD stops immediately on that node until the cloned cluster resource is started.

    Related: How to manage Pacemaker cluster services with systemctl in Linux

  5. Create the Apache HTTPD service resource. 
    $ sudo pcs resource create apache_service systemd:apache2 op monitor interval=30s

    Run pcs configuration changes on a single cluster node only.

    Use systemd:apache2 when that unit is present.

    Related: How to create a Pacemaker resource

  6. Clone the Apache HTTPD service resource across nodes. 
    $ sudo pcs resource clone apache_service

    A clone starts one instance per eligible node by default.

    Related: How to create a cloned resource in Pacemaker
    Related: How to set Pacemaker clone resource options

  7. Verify the cloned resource status. 
    $ sudo pcs status resources
  * Clone Set: dummy-check-clone [dummy-check]:
    * Started: [ node-01 node-02 node-03 ]
##### snipped #####
  * Clone Set: apache_service-clone [apache_service]:
    * Started: [ node-01 node-02 node-03 ]
  8. Send a test request to each node to confirm Apache HTTPD is serving traffic. 
    $ curl -sI http://192.0.2.11/
HTTP/1.1 200 OK
Date: Thu, 01 Jan 2026 00:49:46 GMT
Server: Apache/2.4.58 (Ubuntu)
Last-Modified: Thu, 01 Jan 2026 00:28:55 GMT
ETag: "3-64748ad945d38"
Accept-Ranges: bytes
Content-Length: 3
Content-Type: text/html

$ curl -sI http://192.0.2.12/
HTTP/1.1 200 OK
Date: Thu, 01 Jan 2026 00:49:46 GMT
Server: Apache/2.4.58 (Ubuntu)
Last-Modified: Thu, 01 Jan 2026 00:28:59 GMT
ETag: "3-64748adcb6328"
Accept-Ranges: bytes
Content-Length: 3
Content-Type: text/html
  9. Update client routing to distribute traffic across active nodes.

    Use a load balancer or DNS records that include every active node address, and configure health checks to remove failed nodes from rotation.

    Related: How to plan traffic distribution for active-active PCS services

  10. Run a failover test with traffic distribution in place.

    Related: How to run a Pacemaker failover test with PCS