Context server relies on Elasticsearch to discover and configure its cluster. You just need to install multiple context servers on the same network, and enable the discovery protocol in $MY_KARAF_HOME/etc/org.apache.unomi.persistence.elasticsearch.cfg file :

discovery.zen.ping.multicast.enabled=true

All nodes on the same network, sharing the same cluster name will be part of the same cluster.

It is recommended to have one node dedicated to the context server, where the other nodes take care of the Elasticsearch persistence. The node dedicated to the context server will have node.data set to false.

2 nodes configuration

One node dedicated to context server, 1 node for elasticsearch storage.

Node A :

node.data=true
numberOfReplicas=0
monthlyIndex.numberOfReplicas=0

Node B :

node.data=false
numberOfReplicas=0
monthlyIndex.numberOfReplicas=0

3 nodes configuration

One node dedicated to context server, 2 nodes for elasticsearch storage with fault-tolerance

Node A :

node.data=false
numberOfReplicas=1
monthlyIndex.numberOfReplicas=1

Node B :

node.data=true
numberOfReplicas=1
monthlyIndex.numberOfReplicas=1

Node C :

node.data=true
numberOfReplicas=1
monthlyIndex.numberOfReplicas=1

Specific configuration

If multicast is not allowed on your network, you’ll need to switch to unicast protocol and manually configure the server IPs. This can be done by disabling the elasticsearch automatic discovery in $MY_KARAF_HOME/etc/org.apache.unomi.persistence.elasticsearch.cfg :

discovery.zen.ping.multicast.enabled=false

And then set the property discovery.zen.ping.unicast.hosts in $MY_KARAF_HOME/etc/elasticsearch.yml files :

discovery.zen.ping.unicast.hosts: [‘192.168.0.1:9300', ‘192.168.0.2:9300']

More information and configuration options can be found at : https://www.elastic.co/guide/en/elasticsearch/reference/current/modules-discovery.html

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