4.3.1 Dispatcher
The Dispatcher distributes the load to servers contained in a WAS cluster. This process is known as IP spraying.
The Dispatcher can provide load balancing for the following protocols
- HTTP
- HTTPS
- FTP
- NNTP
- IMAP
- POP3
- SMTP
- Telnet
Dispatcher decides which server will handle a certain TCP/IP connection based on the weight of each server in the cluster. The weight is the value that determines the number of connections that each server receives. The weight can be fixed in the configuration or it can be dynamically calculated by Dispatcher.
If you choose to configure the weight of the servers and set it as a fixed value, it will not change no matter the conditions of the balanced servers. For example, if you configure a cluster containing two servers, and you set the weight of the first server to 1, and the weight of the second server to 2, the second server will always receive twice the load as the first server. The only exception to this is when an Advisor detects a failed server.
If you choose to work with dynamic weights (which is the default option), Dispatcher will calculate the load of each balanced server dynamically. In our previous example, if the response time of the second server was slower than the response time of the first server, it would now be possible to detect this and generate the correct weight value according to the real conditions of each server.