[mapguide-internals] RE: Please review RFC 66

Fri Jun 19 05:44:44 EDT 2009

Hi all,

   Thank you for your quick response. Your suggestions are very appreciated!

To Trevor & Jason,
This task is not about "session recreation". It pings the MapGuide server periodically to avoid session timeout as Fusion does, and we don't support recreate a session from one which is timeout. Actually there was discussion about real "session recreation", but it's scoped out due to time/resource limitation. 

To Haris,
Yes, there is setting to configure how often Ajax viewer will ping server. The default value is 5 minutes, the same as Fusion does. And you can set it to a longer time, or turn it off.

To Chris,
Thank you for your reminder. Your suggestion is very good. If server fails the browser should stop pinging server again and again. It totally makes sense.

Thanks & regards,
Christine

-----Original Message-----
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Today's Topics:

   1. RE: Please review RFC 66 (Trevor Wekel)
   2. RE: Please review RFC 66 (Jason Birch)

----------------------------------------------------------------------

Message: 1
Date: Wed, 17 Jun 2009 10:29:25 -0700
From: Trevor Wekel <trevor.wekel at autodesk.com>
Subject: RE: [mapguide-internals] Please review RFC 66
To: MapGuide Internals Mail List <mapguide-internals at lists.osgeo.org>
Message-ID:
	<D8305E7409B5DB46A9D6219E54E1CF1A2A6211EC6A at ADSK-NAMSG-01.MGDADSK.autodesk.com>

Content-Type: text/plain; charset="us-ascii"

Hi everyone,

Session recreation is tricky business.  You would need to implement two HTTP APIs to make this work.  SAVESESSION(sessionId) would download the user's session repository as an mgp.  The second API, LOADSESSION(sessionId, mgp) would upload the same mgp into a newly created session repository on another server.  The overall flow would be something like this:

SAVESESSION --> mgp downloaded to viewer
Original server goes offline
Exceptions thrown
Viewer calls CREATESESSION to get a new session on another server
Viewer calls LOADSESSION(newSessionId, downloaded mgp)
Viewer sets appropriate center/scale

But there is a big catch here.  The downloaded mgp will contain old session repository references, eg, "Session:xxyyzz//Temporary.LayerDefinition" for any dynamically generated resources (layers, SDF feature sources, selection, etc).  LOADSESSION will have to fixup all of these references during the load process.

Thanks,
Trevor 

-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Chris Claydon
Sent: Wednesday, June 17, 2009 9:14 AM
To: MapGuide Internals Mail List
Subject: RE: [mapguide-internals] Please review RFC 66

I thought I saw some code go into Fusion trunk to allow the user to specify a certain amount of map state when loading a layout, so we might be able to do a little better than a full browser refresh. I was thinking more along the lines of re-creating any session-resident resources and preserving as much state information as is available (and applicable) within the client.

I can't claim to have given this any in-depth analysis, however.

Chris.

-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Jason Birch
Sent: Wednesday, June 17, 2009 9:03 AM
To: MapGuide Internals Mail List
Subject: RE: [mapguide-internals] Please review RFC 66

What would this user prompt look like?

I think that with the current users if your connection is dropped you need a full browser refresh to re-establish your session and all of the objects associated with it.  If that's the case, would the user be told to "press refresh in your browser", or be provided with a button to do the same, or... 

Jason

-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Chris Claydon
Sent: Wednesday, June 17, 2009 7:25 AM
To: MapGuide Internals Mail List
Subject: RE: [mapguide-internals] Please review RFC 66

I agree that this should be configurable. My preference is to switch it on by default. Fusion already pings the server periodically to keep the session alive, and I think it prevents more problems than it causes. However, it needs to be updated so that if the session no longer exists, it stops trying, and prompts the user to re-connect. - with the current setup, the error log can get filled with "Session not found" errors if the server is re-started (and thus the original session is lost). I'm pretty sure there is already a Trac ticket logged against Fusion for this issue.

Chris.

-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org [mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Haris Kurtagic
Sent: Wednesday, June 17, 2009 6:35 AM
To: MapGuide Internals Mail List
Subject: RE: [mapguide-internals] Please review RFC 66

For Keep alive script there will be option to turn it on or off ?

I don't like idea of clients making constant auto requests to server.
Perhaps for some applications it make sense but I think that should be
optional to turn it on (include script).

Haris

-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org
[mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of
Christine Bao
Sent: Wednesday, June 17, 2009 5:12 AM
To: mapguide-internals at lists.osgeo.org
Subject: [mapguide-internals] Please review RFC 66

Hi all,

     RFC 66 -
Failover<https://trac.osgeo.org/mapguide/wiki/MapGuideRfc66> is posted.
Would you please review it? Thank you in advance.

Thanks & regards,
Christine

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------------------------------

Message: 2
Date: Wed, 17 Jun 2009 10:58:23 -0700
From: Jason Birch <Jason.Birch at nanaimo.ca>
Subject: RE: [mapguide-internals] Please review RFC 66
To: MapGuide Internals Mail List <mapguide-internals at lists.osgeo.org>
Message-ID: <26D0CD10F2AC5B4E9C48C3F17D577BEA31963AD0 at kendrick>
Content-Type: text/plain; charset="us-ascii"

I'm not sure that it's necessary to recreate the whole session; when it times out, often it's too late to save.  Just enough to recreate the user's current view state (extent, layer state, possibly selection, etc) would be a good best-effort.

Jason

-----Original Message-----
From: Trevor Wekel
Sent: Wednesday, June 17, 2009 10:29 AM
Subject: RE: [mapguide-internals] Please review RFC 66

Session recreation is tricky business.  You would need to implement two HTTP APIs to make this work.  SAVESESSION(sessionId) would download the user's session repository as an mgp.  The second API, LOADSESSION(sessionId, mgp) would upload the same mgp into a newly created session repository on another server.  The overall flow would be something like this:

SAVESESSION --> mgp downloaded to viewer
Original server goes offline
Exceptions thrown
Viewer calls CREATESESSION to get a new session on another server
Viewer calls LOADSESSION(newSessionId, downloaded mgp)
Viewer sets appropriate center/scale

But there is a big catch here.  The downloaded mgp will contain old session repository references, eg, "Session:xxyyzz//Temporary.LayerDefinition" for any dynamically generated resources (layers, SDF feature sources, selection, etc).  LOADSESSION will have to fixup all of these references during the load process.

------------------------------

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