Set Up Load Balancing

The core component of an HA setup is its load balancer.

The load balancer installation and configuration processes covered here are intended to help you set up your HA environment, but they are outside the scope of FileCloud Support.

We use HaProxy in an Ubuntu 22.04 environment in our example, but you may adapt our instructions to the load balancing software and environment that best serves your needs. This example uses HTTP but can be expanded to use HTTPS as well.

Load Balancer

The load balancer is the component that distributes incoming requests among a group of servers. In this example, the load balancer is HaProxy (http://www.haproxy.org/). HaProxy is a high performance load balancer that allows you to scale your FileCloud deployment quickly.

NOTE: Before starting the installation, ensure the servers are already available and their IP addresses are known.

Setting up Ha-Proxy

Use the apt-get command to install HAProxy.
```
apt-get install haproxy
```
Enable HAProxy to be started by the init script.
```
vi /etc/default/haproxy
```
Set the ENABLED option to 1.
```
ENABLED=1
```

Move the default config file to create a new default configuration file.

mv /etc/haproxy/haproxy.cfg /etc/haproxy/haproxy.cfg.save
vi /etc/haproxy/haproxy.cfg

Add the following in the empty haproxy.cfg file.
The log directive mentions a syslog server to which log messages are sent. On Ubuntu, rsyslog is already installed and running but it doesn't listen on an IP address. We'll modify the config files of rsyslog later.
The maxconn directive specifies the number of concurrent connections on the frontend. The default value is 2000 and should be tuned according to your VPS' configuration.
The user and group directives change the HAProxy process to the specified user/group. These shouldn't be changed.
```
global
    log 127.0.0.1 local0 notice
    maxconn 2000
    user haproxy
    group haproxy
```

Defaults

This section demonstrates how to specify default values. The values to be modified are the various timeout directives. The connect option specifies the maximum time to wait for a connection attempt to a VPS to succeed.

The client and server timeouts apply when the client or server is expected to acknowledge or send data during the TCP process. HAProxy recommends setting the client and server timeouts to the same value.

The retries directive sets the number of retries to perform on a VPS after a connection failure.

The option redispatch enables session redistribution in case of connection failures. So session stickiness is overridden if a VPS goes down.

defaults
    log global
    mode http
    option httplog
    option dontlognull
    retries 3
    option redispatch
    timeout connect 5000
    timeout client 10000
    timeout server 10000

Host Configuration

This contains the configuration for both the frontend and backend and shows how to configure HAProxy to listen on port 80 for filecloud (which is just a name for identifying the application).

The stats directives enable the connection statistics page and protect it with HTTP Basic authentication using the credentials specified by the stats auth directive.

This page can be viewed with the URL mentioned in stats uri, so in this case, it is http://<loadbalancerip>/haproxy?stats;

The balance directive specifies the load balancing algorithm to use. Options available are Round Robin (roundrobin), Static Round Robin (static-rr), Least Connections (leastconn), Source (source), URI (uri) and URL parameter (url_param).

Information about each algorithm can be obtained from the official documentation.

The server directive declares a backend server with the syntax:

server <name> <address>[:port] [param*]

The names used for the three webservers in these instructions are Ha-WS1, Ha-WS2, Ha-WS3.

In the directive server Ha-WS1 xx.xx.xx.xx:80, replace xx.xx.xx.xx with the actual IP address of the app server nodes.

listen filecloud 
    bind 0.0.0.0:80
    mode http
    stats enable
    stats uri /haproxy?stats
    stats realm Strictly\ Private
    stats auth  proxyuser:proxypassword
    balance roundrobin
    option http-server-close
    timeout http-keep-alive 3000
    option forwardfor
    server Ha-WS1 xx.xx.xx.xx:80 check
    server Ha-WS2 xx.xx.xx.xx:80 check
    server Ha-WS3 xx.xx.xx.xx:80 check

Starting Ha-Proxy

From a command line, start haproxy, using the following command:

service haproxy start