Set Up Kaazing Gateway as a Load Balancer

Load balancing is used to balance client connection loads for a group of Gateways that have been configured as a cluster using the cluster service. For more information, see Configure a Kaazing Gateway Cluster. You can configure load balancing using a third-party load balancer, but this procedure describes how to use the built-in load balancing features of the Gateway.

To configure load balancing, you configure each Gateway in the cluster with a balancer service. The balancer service has accept elements for each URI that will be balanced across the cluster. Each cluster member configured with a balancer service acts as a load balancer to the other members.

Next, in the service elements on each Gateway, you add balance child elements containing the same URIs you configured in the balancer service.

Before You Begin

This procedure is part of Configure the Gateway for High Availability:

Using the Gateway to Support High Availability
Configure a Kaazing Gateway Cluster
Set Up Kaazing Gateway as a Load Balancer
Troubleshoot Kaazing Gateway Clusters and Load Balancing

To Set Up The Gateway as a Load Balancer

Configure a balancer service in each Gateway that will participate in load balancing (each cluster member). The balancer service has an accept for each URI that will be balanced across participating Gateways. These are the public URIs that clients will use when connecting to the cluster for the first time.
```
<service>
  <name>Echo balancer</name>
  <accept>ws://balancer.example.com:8081/echo</accept>
  <accept>wss://balancer.example.com:9091/echo</accept>

  <type>balancer</type>

  <accept-options>
      <ws.bind>192.168.2.10:8081</ws.bind>
      <wss.bind>192.168.2.10:9091</wss.bind>
  </accept-options>

</service>
```
Important:
- The ws.bind element in accept-options is used to bind the public URI in the accept element to the local IP address of the cluster member. This allows the accept URIs in the balancer service to be identical on every cluster member. Only the ws.bind element needs to be unique in each cluster member (contain the local IP address of that cluster member). For more information, see protocol.bind.
- For production environments, the hostname in the accept element must resolve in DNS to the IP addresses of every cluster member. Multiple DNS A resource records should be registered for the hostname in the accept URI, with each A record mapping the hostname to the IP address of one cluster member. When a client resolves the hostname of the accept URI in DNS, it will receive the IP address of a cluster member and connect. To register these DNS records, you will need access to the public DNS zone for the hostname, or the assistance of your network administrator or Internet Service Provider (ISP). All ISPs provide ways for their customers to update their DNS zones with new hostnames and IP addresses.

Configure the services of each cluster member (for example, the echo service) with a balance element for each URI accepted by the balancer service. Clients will use these URIs to connect to the service.

<service>
  <name>Echo</name>
  <accept>ws://node1.example.com:8081/echo</accept>
  <accept>wss://node1.example.com:9091/echo</accept>
  <balance>ws://balancer.example.com:8081/echo</balance>
  <balance>wss://balancer.example.com:9091/echo</balance>

  <type>echo</type>

  <cross-site-constraint>
    <allow-origin>http://directory.example.com:8080</allow-origin>
  </cross-site-constraint>
  <cross-site-constraint>
    <allow-origin>https://directory.example.com:9090</allow-origin>
  </cross-site-constraint>

</service>

Important:

The balance and accept element URIs in a service must use the same port number and path. The hostnames in the URIs may be different.
For information on the order of subordinate elements in a service, see the service element reference.

Ensure that each Gateway participating in load balancing is configured with a cluster service, as described in Configure a Kaazing Gateway Cluster.
Configure client applications to connect to the cluster using the URI(s) configured in the balancer service (for example, ws://balancer.example.com:8081/echo or wss://balancer.example.com:9091/echo).
Start all cluster members.

Example Configuration

Here is an example of a Gateway configured as a cluster member and load balanced for both secure and unsecured Echo services:

<!-- Cluster service -->
<cluster>
  <name>MyCluster</name>
  <accept>tcp://192.168.2.10:5942</accept>
  <connect>udp://224.2.2.44:54327</connect>
</cluster>

<!-- Balancer service for connections -->
<service>
  <name>Echo balancer</name>
  <accept>ws://balancer.example.com:8081/echo</accept>
  <accept>wss://balancer.example.com:9091/echo</accept>

  <type>balancer</type>

  <accept-options>
      <ws.bind>192.168.2.10:8081</ws.bind>
      <wss.bind>192.168.2.10:9091</wss.bind>
  </accept-options>
</service>

<!-- Echo service for connections -->
<service>
  <name>Echo</name>
  <accept>ws://node1.example.com:8081/echo</accept>
  <accept>wss://node1.example.com:9091/echo</accept>

  <balance>ws://balancer.example.com:8081/echo</balance>
  <balance>wss://balancer.example.com:9091/echo</balance>

  <type>echo</type>

  <cross-site-constraint>
    <allow-origin>http://directory.example.com:8080</allow-origin>
  </cross-site-constraint>
  <cross-site-constraint>
    <allow-origin>https://directory.example.com:9090</allow-origin>
  </cross-site-constraint>
</service>

Next Step

You have completed high availability configuration using the Gateway.

Notes

To set up a cluster locally for testing purposes, see Configure a Two-Member Local Demo Cluster.