> For the complete documentation index, see [llms.txt](https://docs.apryse.com/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://docs.apryse.com/web/get-started/faq/load_balancing.md).

# Manual Load Balancing with HAProxy

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WebViewer Server comes with a load balancer known as `HAProxy` located at our pdftron/wv-loadbalancer repository on DockerHub. This can be used in conjunction with WebViewer Server to load balance.

This guide details how to manage load balancing using the HAProxy image, in a way that is extensible to any environment.

### How it works

HAProxy contains network entries called `webAwebBwebC` ... and so on. These entries indicate the location of a server that HAProxy can send requests to. The methods here will modify these entries to point at the correct server.

By default WebViewer Server does all load balancing using the [leastconn](https://cbonte.github.io/haproxy-dconv/1.9/configuration.html) method. This sends incoming requests to servers with the smallest number of active connections.

### Setting initial servers

You can set the initial locations of these `webX` entries by setting the environment variables `INITIAL_NODE_AINITIAL_NODE_B` ... up to `INITIAL_NODE_F` on the `wv-loadbalancer` image. HAProxy will initially send requests to any healthy and responding servers set in these variables.

### Setting servers dynamically

To set servers dynamically with HAProxy you can take advantage of something known as [TCP Management](https://cbonte.github.io/haproxy-dconv/1.9/management.html) - this can be used to change these `webX` entries to the current location of a server.

There are several ways to send requests to the server with this method, but all commands to HAProxy will be sent with the same structure.

`set server nodes/[webX] addr [WVS ip address] [WVS port]`

* Locally in the server hosting HAProxy using sockets - this can be done through a socket communication application such as socat

{% tabs %}
{% tab title="Bash" %}
{% code lineNumbers="true" %}

```bash
socat /var/run/hapee.sock set server nodes/webA addr 192.168.1.1 8090
```

{% endcode %}
{% endtab %}
{% endtabs %}

* Remotely by setting `ENABLE_TCP_MANAGEMENT` to true on the Docker image and sending requests to the TCP Management port `4893` wherever the balancer is located. The following code does this using Node.js.

{% tabs %}
{% tab title="JavaScript" %}
{% code lineNumbers="true" %}

```js
const connectSocket = (balancer) => {
      return new Promise((resolve, reject) => {
        var socket = new net.createConnection(4893, balancer);
        socket.on('connect', () => {
            resolve(socket);
        });

        socket.on('error', () => {
            reject(balancer + ": Balancer not online.");
        });
      });
};
const writeSocket = (command, socket, forceClose) => {
      return new Promise((resolve, reject) => {
          console.log(command);
          socket.write(command, (error, data) => {
            if (error) {
              console.log(error);
              reject();
            }
          });

          socket.on('data', (data) => {
              //console.log("balancer response:" + data);
              socket.end();
              resolve(data);
          });
      });
};
command = "set server nodes/webA addr 192.168.1.1 8090\n"
var socket = await connectSocket("insert balancer ip here");
await writeSocket(command, socket, false)
```

{% endcode %}
{% endtab %}
{% endtabs %}

The above code sets `webA` to be the Webviewer Server at `192.168.1.1:8090`. HAProxy will now send `webA` requests to this server.

Whenever a change occurs, you can dynamically rewrite remotely using the above code. The changes will instantly occur. More commands can be found at the [HAProxy Management documentation](https://cbonte.github.io/haproxy-dconv/1.9/management.html)


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