OpenMeetings 2.1 or later is required to use clustering. One database is used for all OpenMeetings servers, so all database tables are shared across OM instances. Certain folders should be shared between all servers to allow access to the files/recording.

Configuration

Multiple OM servers should be set up as described in Installation
All servers should be configured to have same Time zone (To avoid Schedulers to drop user sessions as outdated)
All servers should be configured to use the same DB

Network

Multicast should be set up on all servers
Here are the steps for *nix like systems Reference article

Check your network interface supports multicast by running the following command in a terminal window:
```
ifconfig -a
```
When you see MULTICAST against your network interface, it means your kernel is compiled with Multicast option and your network interface supports it.
Check if multicast routing is configured:
```
netstat -nr
```
If you don’t see an IP in the range of 224.0.0.0 – 239.255.255.255 in the first table, it means you need to add your desired mutlicast address to your routes table.
To add the multicast address:
```
sudo route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0
```
NOTE: ensure eth0 corresponds to your network interface name
Make sure you run this command on all servers you want to be multicast enabled.
Using netstat check if the multicast IP is visible in your route table (see step 2.)
Using tcpdump and ping check if your server is able to multicast.
Run the following command on all the servers.
```
sudo tcpdump -ni eth0 host 224.0.0.0
```
Run the following command on any server.
```
ping -t 1 -c 2 224.0.0.0
```
Check all servers receiving pings

Run

sudo route -v delete -net 224.0.0.0 netmask 240.0.0.0

to disable multicast

Database

All servers should be configured to use the same database. It can be on the server or on the one node of the cluster.

NOTE: Db other than H2 should be used

Add users who can connect to the database remotely
Update /opt/om/webapps/openmeetings/WEB-INF/classes/META-INF/persistence.xml set correct server address, login and password. Also uncomment following line:
```
<property name="openjpa.RemoteCommitProvider" value="tcp(Addresses=127.0.0.1)" />
```

File systems

If files and recordings using the same physical folders the files and recordings will be available for each node. You can do this using Samba or NFS, for example. For using NFS do the following:

To ease upgrade process set OM data dir to some external folder: for ex. /opt/omdata
Install NFS to the data server. In the file /etc/exports add the following lines:
```
/opt/omdata 10.1.1.2(rw,sync,no_subtree_check,no_root_squash)
						
```
Here 10.1.1.2 - is node ip for NFS remote access. Add these lines for all nodes except node with folders.
Install NFS common tools to other nodes. In the file /etc/fstab do the following:
```
10.1.1.1:/opt/omdata /opt/omdata nfs timeo=50,hard,intr
						
```
Here 10.1.1.1 – data server ip. And run the command:
```
mount -a
```

OM nodes configuration

In the file /opt/om/webapps/openmeetings/WEB-INF/classes/hazelcast.xml:

Set instance-name for each server to unique value
Set server.url for each server to full public URL of this server (please NOTE using of numeric IP address might broke HTTPS))

Comment out/delete following blocks:

<network>
	<join>
		<auto-detection enabled="false"/>
		<multicast enabled="false"/>
		<tcp-ip enabled="false"/>
		<aws enabled="false"/>
	</join>
</network>

<property name="hazelcast.discovery.enabled">false</property>

Un-comment following block (ensure it contains valip parameters):

	<network>
		<join>
			<multicast enabled="true">
				<multicast-group>224.0.0.0</multicast-group>
				<multicast-port>54327</multicast-port>
				<multicast-time-to-live>32</multicast-time-to-live>
				<multicast-timeout-seconds>2</multicast-timeout-seconds>
			</multicast>
		</join>
		<interfaces enabled="true">
			<interface>192.168.1.*</interface>
		</interfaces>
	</network>

In case there are more than one network interface with multicast support and/or additional hazelcast configuration is required Based on the following documentation: https://docs.hazelcast.org/docs/4.0/manual/html-single/index.html

Ensure everything works as expected

Set up the cluster and login with two users, go to the same room (also check before room entering that the status page with the room list shows the correct number of participants before entering the room). You should login to the same server initially, the server will redirect you for the conference room to the appropriate server automatically. Both users should be in the same room.
Do the same with only two users but go to _different_ rooms. The calculation should send both users to different servers, cause based on the calculation two different rooms on a cluster with two nodes should go exactly one room for each node. You can now login really to node1 and node2 of your cluster while those users are loggedin and go to Administration > Connections and check in the column "Server Name" where they are located. They should be on different server.