[mapguide-dev] Session Affinity RFC

[Trevor Wekel]

Hey guys, here's my 2 bits after doing some research into hardware load
balancers:
 
Hardware load balancers range in price from $2500 to $30000+ depending
on features and performance.  The higher end ones usually require IT
resources to configure.  But from what I understand, setting up session
affinity on a load balancer is not that difficult if you already know
how to set it up to do basic (round-robin) load balancing.  So if you
already have an external load balancer doing round robin, then it's not
much of a leap to add session affinity.
 
Hardware balancers typically expose another load balanced IP address in
addition to the original IP addresses of the individual web servers.
This allows simultaneous access to both the load balanced cluster and
the individual machines.  For MapGuide, the load balanced web server IP
could serve general clients while the original web server IP's could
still be used with Studio and the Admin.
 
This could easily be replicated by installing multiple Web Extensions.
Installing "local" web extensions on all of the server machines gives
direct access to those machines for Admin and the Studios.  "Remote" web
extensions on dedicated machines could then be set up to round robin
against the already installed servers.  This gives us all the
functionality of the typical load balanced setup.
 
Round robin balancing and session affinity are both "routing"
technologies.  Personally, I think it makes sense to implement them both
in the same place.  If we are implementing session affinity, then I
think we should also include round-robin load balancing.  Otherwise, we
are forcing the MapGuide use base to invest time and/or money
implementing other solutions for load balancing.
 
 
Thanks,
Trevor
 

  _____  

From: Chris Claydon 
Sent: Friday, November 17, 2006 2:57 PM
To: dev at mapguide.osgeo.org
Subject: RE: [mapguide-dev] Session Affinity RFC



I like your suggestions, Tom. This approach would allow a user to hook
up a load balancer without changing any configuration at the web tier
level. Having the web tier connect to a site server that it is not
configured to know about seems a little strange, but I don't think that
it poses a security risk - you can only connect to a server if the
session you need exists on it. So you wouldn't be able to make an
unauthorized connection.

 

I don't think anyone would want to operate Studio (or Web Studio)
through a load-balanced environment. You'd always want to make your
changes on a specific site. Imposing the same restriction for the admin
pages seems fair also.

 

Chris.

 

  _____  

From: Tom Fukushima 
Sent: November 17, 2006 1:32 PM
To: dev at mapguide.osgeo.org
Subject: RE: [mapguide-dev] Session Affinity RFC

 

Hi Chris,

 

I was reading over this with the intent of motioning it for approval,
but thought of the following.

 

The RFC says that the list of available site servers will be listed in
the web tier config file so that the web tier can do some rudimentary
load balancing.  But since the load balancer is already doing this, I
don't think that it is necessary for the web tier to do it again.  With
this in mind, I think that we can simplify things a little more:

1) Each Web Tier only knows about 1 site server (as it is today) and if
a request that doesn't have a session (e.g., request to create a
session) comes to it, the request goes to the web tier's site server
(like it does today).

2) If a request with a session comes in, the Web Tier uses the IP
embedded in the session ID to route the request.  Note that the IP does
not have to be registered in the config file of that web tier.

3) In order to bring up the server admin pages, we only support going
directly to a particular web tier.  We do not support going through the
load balancer.

4) In order to author using Studio or Web Studio, we only support going
directly to a particular web tier.  We do not support going through the
load balancer.

 

Points 3 and 4 above are to make things easier in case it might be tough
to do them. (I don't see Studio mentioned in the RFC.)

 

Cheers

Tom

 

  _____  

From: Chris Claydon 
Sent: Wednesday, November 01, 2006 3:47 PM
To: dev at mapguide.osgeo.org
Subject: [mapguide-dev] Session Affinity RFC

I have just posted a draft of the RFC for "Session Affinity" in MGOS to
the following location:

 

http://wiki.osgeo.org/index.php/MG_RFC_3_-_Session_Affinity

 

Please take a look, and post any feedback to this group.

 

Thank you,

 

Chris Claydon.

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