Backend servers

Varnish has a concept of “backend” or “origin” servers. A backend server is the server providing the content Varnish will accelerate.

Our first task is to tell Varnish where it can find its backends. Start your favorite text editor and open the relevant VCL file.

Somewhere in the top there will be a section that looks a bit like this.:

# backend default {
#     .host = "127.0.0.1";
#     .port = "8080";
# }

We remove the comment markings in this text stanza making the it look like.:

backend default {
    .host = "127.0.0.1";
    .port = "8080";
}

Now, this piece of configuration defines a backend in Varnish called default. When Varnish needs to get content from this backend it will connect to port 8080 on localhost (127.0.0.1).

Varnish can have several backends defined you can even join several backends together into clusters of backends for load balancing purposes.

backends can also be empty or ‘none’ with the following syntax.:

backend default none;