Configuring the Data Service

The data service configuration is specified in data-server-cluster element in the appian-topology.xml file, located in both the <APPIAN_HOME>/ae/data-server/conf/ and <APPIAN_HOME>/ae/conf directories:

1
2
3
4
5
6
<topology>
    ...
    <data-server-cluster>
        <data-server host="machine1.example.com" port="5400" rts-count="2"/>
    </data-server-cluster>
</topology>

For a high availability configuration, specify three instances of the data service on different machines:

1
2
3
4
5
6
7
8
<topology>
    ...
    <data-server-cluster>
        <data-server host="machine1.example.com" port="5400" rts-count="2"/>
        <data-server host="machine2.example.com" port="5400" rts-count="2"/>
        <data-server host="machine3.example.com" port="5400" rts-count="2"/>
    </data-server-cluster>
</topology>

The data-server-cluster configuration must be specified in appian-topology.xml. The appian-topology.xml file must be copied from <APPIAN_HOME>/conf/ into <APPIAN_HOME>/data-server/conf/ before starting the data service. Copies of the topology file in each location must always be in sync, irrespective of the configurations specified.

Node

A data-server node element must be present and must be structured similarly to the following:

1
<data-server host="machine3.example.com" port="5400" rts-count="2"/>

If there is no data-server node element specified, the following error is printed in watchdog.log:

"ERROR com.appian.data.server.Watchdog - At least one data-server node must be specified"

Host

Set the host attribute in the data-server element to the name of the machine hosting the data service. If the host is not specified, the following error is printed in watchdog.log:

"ERROR com.appian.data.server.Watchdog - data-server host must be specified"

Port

The port attribute can be defined on both the data-server-cluster and the data-server elements. If defined on both, the data-server element takes precedence. If not supplied, the default port number is 5400.

In order for the data service to function properly, make sure that you open all of the required ports. See Port Usage for more information.

Real-time store count

The rts-count attribute determines the number of real-time stores in the data service. Multiple real-time stores provide horizontal read scalability. Appian supports running exactly two instances of the real-time store only. When configuring the attribute value, set it to rts-count="2".

Changing the topology

Topology changes can include:

  • Add or remove data service nodes.
  • Change the host name.
  • Change the port.
  • Change the real-time store count.

To make these changes, you'll need to make configuration changes to the data-server-cluster parameter and restart both the data server and the application server by following these steps:

  1. Stop the data service on all of the servers:
    • <APPIAN_HOME>/data-server/bin/stop.sh (.bat on Windows)
  2. Delete the <APPIAN_HOME>/ae/data-server/node/election directory from all the servers. This directory contains runtime data that needs to be deleted when certain topology changes are made.
  3. If adding nodes (for example, when migrating from a single node to High Availability), copy the <APPIAN_HOME>/ae/data-server/data directory to the new servers.
  4. Make the required topology change on all of the servers.
  5. Start the data service on all of the servers in any order:
    • <APPIAN_HOME>/data-server/bin/start.sh (.bat on Windows)
  6. Restart the application server on all servers:
    • To stop the server: <APPIAN_HOME>/tomcat/apache-tomcat/bin/stop-appserver.sh (.bat on Windows)
    • To start the server: <APPIAN_HOME>/tomcat/apache-tomcat/bin/start-appserver.sh (.bat on Windows)
Open in Github Built: Fri, Sep 23, 2022 (01:18:20 PM)

On This Page

FEEDBACK