Subject: RE: [BXXPwg] Redirect Feature for BEEP (continued...)

From: "Bob Wyman" <[email-masked]>
Date: Mon, 2 Jul 2001 12:49:25 -0400

Marshall Rose wrote:
>could you give me an example or two as to 
> how this would be used in practice.

Use cases:
1. A Beep server has become well-known as a provider of support for 10
profiles. Due to excessive load on the server, it is decided to
redistribute support for the profiles between two machines. So, the
redirect feature and a "permanently unavailable" error code would be
used to inform users where to find support for profiles moved off the
original server.

2. A number of Beep servers are sharing the task of supporting one or
more profiles. However, from time to time, the load becomes unbalanced
between the servers. In this case, heavily loaded servers could
temporarily redirect new connections to machines that have more
capacity.

3. A company has two Beep servers that each support the same profile,
however, because of quality of service requirements one group of users
is required to use one of the servers while a second group uses a
different server. So, whenever someone attempts to connect to the wrong
machine, they would be redirected to the machine that they belong on.
The company could then post the address of only one Beep server and then
let the permanent redirects sort people out as they arrive.

4. A Beep server needs to be brought down for maintenance. (i.e.
software/hardware upgrade, database reorg, etc.) A secondary system is
available to take load during the downtime. So, the server administrator
would use a temporary redirect to redirect all new connections to the
secondary system and after some reasonable period would terminate
existing sessions. When the primary was restored, the process would be
reversed.

5. A Beep server needs to be brought down for maintenance but there is
no secondary or backup server to take the load. If it is simply software
maintenance, the server administrator could replace the existing server
with a "dummy" server that responded to all start requests by issuing a
"temporarily unavailable" message and "availableAfter" some specific
time. Clients should not attempt to access the server until after the
time specified.

6. A Beep server is scheduled to be brought down for maintenance on
Saturday at 2:00am and will be down for four hours. This is known two
weeks in advance. So, the system administrator would cause his servers
to publish "availableUntil" to indicate the intent to bring the service
down and "availableAfter" to show when it should come back. Email
messages saying "servers will be down on Saturday" would NOT be sent to
the 10,000 employees of the company hosting the server...

Hopefully, these examples will help in crossing the chasm.

		bob wyman

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---

From: "Roy T. Fielding" <[email-masked]>
Date: Mon, 2 Jul 2001 13:49:54 -0700

> used to inform users where to find support for profiles moved off the

This is what IP load balancers are for -- waiting until the beep session
has been established means it has already taken on the load.

> temporarily redirect new connections to machines that have more

Again, load balancers do this.

> let the permanent redirects sort people out as they arrive.

This is an application-level redirect -- it belongs in the profile protocol.

> existing sessions. When the primary was restored, the process would be

Load balancer.

> time. Clients should not attempt to access the server until after the

A replacement application for the profile.

> the 10,000 employees of the company hosting the server...

Another application profile issue.

> Hopefully, these examples will help in crossing the chasm.

Load balancing needs to be handled before connections are accepted.
Application redirects need to be handled after the profile is established
(because there may be many different types of redirect, like in HTTP).
That is why this kind of feature doesn't need to be in BEEP core.

....Roy