Clustering¶

The SEAL NATS installation package is preconfigured for a single server installation. If you are running PLOSSYS 5 in a cluster, SEAL NATS needs to be installed on every PLOSSYS 5 server. The following instructions refer to a cluster containing three PLOSSYS 5 servers.

Configuring Cluster Server 1¶

Perform the following configuration steps on <server_1>:

Open the /opt/seal/etc/nats.conf configuration file.
Edit the following line. Replace the hostname-of-this-server placeholder by the server name of the current server.
```
server_name: hostname-of-this-server
```
Example
```
server_name: pegasus1
```

Uncomment the following section to activate the preconfigured cluster settings.

# This is for clustering multiple servers together.
cluster {
    # It is recommended to set a cluster name
    name: "seal"

    # Route connections to be received on any interface on port 6222
    port: 6222

    # Routes are protected, so need to use them with --routes flag
    # e.g. --routes=nats-route://ruser:T0pS3cr3t@otherdockerhost:6222
    authorization {
        user: ruser
        password: T0pS3cr3t
        timeout: 2
}

Edit the routes entry. Replace the hostname-of-cluster-server1 placeholder by the server name of the current (= first) server.
```
# Routes are actively solicited and connected to from this server.
routes = [
    nats-route://ruser:T0pS3cr3t@hostname-of-cluster-server1:6222
]
```
Hint - add all NATS services to the list

The NATS services are building a service mesh without a dedicated master. So one route entry pointing to the first (running) service is enough. To ensure that the system comes up again after a complete failure even if the one configured isn't coming up again, you can add all NATS services to the routes list, one line each.
Save the file.
Restart the service:
```
sudo systemctl restart seal-nats
```

Configuring Cluster Server 2 and 3¶

Perform the following configuration steps on <server_2> and <server_3>:

Copy the /opt/seal/etc/nats.conf configuration file created for <server_1> to the same directory on the current server.
Replace the value of the server_name entry by the server name of the current server.
Start the service:
```
sudo systemctl start seal-nats
```