[mapguide-dev] Session Affinity RFC

[Bruce Dechant]

Hi All,

 

The original RFC proposal is for phase 1 of a 3 phase approach to adding
load balancing/fail over to the MapGuide server/web tier. With each
phase it becomes easier and easier to deploy robust and scalable
MapGuide sites. The eventual goal is to remove any single point of
failure in the chain of a MapGuide site.

 

The 3 phases are briefly described below:

 

Phase 1

-          Add some infrastructure so that subsequent phases can be
built on it.

-          Remove the single point of failure when creating a client
session because the web tier will be able to redirect to any of the
known site servers to create the session if needed.

-          Allows administration of any of the site servers known by the
web tier.

-          Adds simple round robin load balancing to site servers known
by the web tier. This load balancing is independent of any hardware load
balancing down for the web tiers.

-          This is the Session Affinity RFC as described in the link
below.

 

Phase 2

-          Build on phase one by adding session repository replication.

-          Remove the single point of failure when a client has session
affinity because if the original site server that created the initial
session is not available an alternate site server can be used.

 

Phase 3

-          Build on phase 2 by adding full library replication

-          Remaining single point of failures are removed now that
replicating entire repository will be done.

 

 

The problem with Tom's suggestions is that it won't support failover and
would still require addressing this at some later date. The sooner we
start to improve failover the better.

 

Thanks,

Bruce

 

  _____  

From: Chris Claydon 
Sent: 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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