[mapguide-internals] RE: MG Object stream serialization/deserialization

[Haris Kurtagic]

Current:
If I interpret correctly your email, you think there is no possibility to
implement application communicating to diff. version of MG using current
common libraries ?

Future:

Regarding versioning of serialization of objects I have experience with two
different large scale application (many objects). In one case versioning is
done "per stream" in another versioning it is "per object".

I prefer "per stream", which means that we use incrementally one version
number for any change on any object serialization/deserialization.
In current MG stream packet there is stream version which is unused.
Of 'course in order to work developers has to be carefully when changing
objects to increase global version number and add handling of previous
versions.

Regarding "default values" or handling previous versions, if there would be
such changes that it is impossible to came up with "default" value for
changed member we can still throw exception "invalid stream.." as it does
now.


Haris



-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org
[mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Trevor
Wekel
Sent: Wednesday, November 04, 2009 12:38 PM
To: MapGuide Internals Mail List
Subject: RE: [mapguide-internals] RE: MG Object stream
serialization/deserialization

Hi Haris,

Yes.  That submission did add a member variable to MgClassDefinition in
order to support schema search related optimizations with some Fdo
providers.

Up to this point, the web extensions API has never supported backward
compatibility from a binary perspective.  You cannot successfully mix and
match different web extensions and servers.  As you have noticed, any change
in object signature breaks binary compatibility.

I believe it will be a huge amount of work to successfully code and test for
backward binary compatibility on an API this large.  If the PSC really wants
to go down this road, I may be willing to support the decision but that
means every contributor will be responsible for maintaining this with every
submission.  The permutations and combinations on the testing effort could
be painful to say the least.  It's hard enough to keep one API version
stable.  A mixed and matched the web extensions and server should probably
be considered a whole other API.  

Sincerely,
Trevor

-----Original Message-----
From: mapguide-internals-bounces at lists.osgeo.org
[mailto:mapguide-internals-bounces at lists.osgeo.org] On Behalf Of Haris
Kurtagic
Sent: November 4, 2009 3:41 AM
To: 'MapGuide Internals Mail List'
Subject: [mapguide-internals] RE: MG Object stream
serialization/deserialization

Hi Trevor,

 

I believe I found when ClassDefinition serialization has changed.

 


Changeset 3905 <http://trac.osgeo.org/mapguide/changeset/3905>  for
trunk/MgDev/Common/PlatformBase/Services/ClassDefinition.cpp
<http://trac.osgeo.org/mapguide/browser/trunk/MgDev/Common/PlatformBase/Serv
ices/ClassDefinition.cpp?rev=3905> 


Timestammp


Author trevorwekel


Ticket  <http://trac.osgeo.org/mapguide/ticket/1002> #1002 Batch Processing
for Get Identity Properties


http://trac.osgeo.org/mapguide/changeset?old=trunk/MgDev/Common/PlatformBase
/Services/ClassDefinition.cpp at 3905
<http://trac.osgeo.org/mapguide/changeset?old=trunk/MgDev/Common/PlatformBas
e/Services/ClassDefinition.cpp at 3905&new=trunk/MgDev/Common/PlatformBase/Serv
ices/ClassDefinition.cpp at 3905>
&new=trunk/MgDev/Common/PlatformBase/Services/ClassDefinition.cpp at 3905


 

 

It feels bit strange that in previous versions schema name from class def.
was omitted ( but that is how 2.1 Beta and MG Ent 2010 works ).

 

This change was really for that ticket  "Batch Processing for Get Identity
Properties" or ?

 

I would like to be able to communicate with MG 2.0.2, MG 2.1 MG Ent. 2010
with one application using standard MG libraries. 

Any idea If that would be possible ?

 

Haris

 

From: Haris Kurtagic [mailto:haris at sl-king.com] 
Sent: Tuesday, November 03, 2009 11:47 PM
To: 'MapGuide Internals Mail List'
Subject: MG Object stream serialization/deserialization

 

Hi ,

 

I have lot of problems while trying to communicate with different versions
of MapGuide. I am developing application which should communicate with MG
using MG common libraries: MapGuideCommon, PlatformBase,...

 

Problem is that I can't find two version of MG which will work one against
other and work equally.

For example I can't use MG OS Beta 2.1.0.3891 version from 2.1 branch
against current branch version. Also for example I can't use any of those
versions against MG Enterprise 2010. 2.1.0.3891 will halt MG Ent. 2010 while
current 2.1 branch will throw exception InvalidStreamHeader.

 

At least one of problems is that ClassDefinition in one version is
serializing SchemaName in another it is not. So those versions can't be used
one against each other.

 

I have two questions:

 

1.  I really can't' find consistency in our svn branches and trunk how and
when is changing how MG objects are serialized/desterilized. I hope somebody
can light me up little bit when/ why are this changes done.

 

2. We don't have any versioning of serialization process of objects. I think
that could be issue ( hopefully one day we could imagine farm of MapGuide's
).

    Can we add versions of objects to serialization process ?

 

I would appreciate any help/ideas how to solve this mess, how to have one
application communicating with different MG versions.

 

Thank you,

Haris

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