Mailing List Archive

Michael Taubert wrote:
> my question is, how does backhand communicate with the other
> backhand-apache's when a request arrives?
>
> i've got two servers, lets call them serv1 and serv2.
> when i request an url on serv1 and the request is passed to serv2,
> which server will reply that request?

So, there are two communications going on. All of the servers
communicate with each other all of the time sharing resource
information. This happens are regular intervals over IP broadcast or IP
multicast.

The servers also communicate in the form of proxying requests.
C(client) asks A, A finds B to be better suited. A asks B, B answers A,
A answers C.

mod_backhand now alos supports HTTP sytle redirecting. In this case, A
will actually tell the C to go make the request again, but this time to
B. This uses trickery in the Host: headers and DNS names.

> does serv2 works on the request and send the reply through serv1,
> or does serv2 reply directly?

It is proxied through serv1. This is becuase mod_backhand hand handle
HTTP/1.0 serialized request/response sequences and redirect each request
to a different machine (if needed). This is impossible with a three-way
handshake that would allow serv2 to responde directly. The three-way
handshake used by products like resonate, and arrowpoint (and others)
work on a TCP/IP basis and cannot handle HTTP/1.0 as effectively.

--
Theo Schlossnagle
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