Re: Finally which ORM tool?

Jon Skeet [C# MVP] wrote:
The decision to be session-based or not is pretty fundamental to an ORM. If you don't want to use sessions, use an ORM which isn't session-
based, such as LLBLGen - but please don't try to suggest that no ORMs should use sessions and manage aliasing and identity issues just because they happen not to be issues for you.

I think you're intentionally mashing my words up here. I never said any such thing. I said that ORMs should not REQUIRE us to use sessions in order to persist and load objects.

What I did NOT say (and which you suggested I did) is that ORMs shouldn't provide session capabilities. I think they're just fine and dandy and a nice feature. However I see no reason why they shouldn't be OPTIONAL and I've provided some pretty good examples why they should be...

That's the great thing about having a choice of frameworks. I have to say that the fact that most ORM frameworks I've come across *do* have identity management suggests that the requirement for it isn't as rare as you seem to be making it out to be. If sessions have no benefit for most people, why do you think the framework developers include them?

Why do we have TCP and TCP/IP ports if developers don't use TCP/IP? The fact is, LOTS of applications use TCP/IP - but that's no reason to force ALL applications to use it. I'm making pretty much the same case here but you don't seem to be following my reasoning very well.

You need to distinguish between the idea of a per-request session and a "per user transaction" session. Again, Hibernate in Action deals with this very well.

Unless by per user transaction you mean a one thread per client model for the server threads then I don't see how this makes a difference. With such a threading strategy the server creates a thread for a client application when it first connects/authenticates and leaves this thread running for the duration of a user's "connection" to the application server... something you could do with a connection based protocol like TCP/IP but stateless protocols like HTTP make this very difficult. Besides which these servers don't scale very well (as soon as you get any volume on the server they grind to a halt swapping out to disk for lack of memory because they've got far too many threads lying around with "session" information in them).

Otherwise though, you're not guaranteed to get the same thread from the thread pool on the server in the request that you make to Save a persistent object as you did in the request that you made to Fetch that persistent object from the app server in the first place - and thus you're not guaranteed to get the same session (with your ORM).

So although a distinction between per-request and per-user sessions is perhaps relevant for a one thread per client thread strategy, I try to stay away from such a beast (for the reasons above). Stateful servers are just plain unreliable, by design.

The Hibernate authors have put in a *lot* of thought when it comes to this kind of thing, and they're certainly *not* just thinking of desktop client/server apps.

Well the DevExpress guys put a lot of thought into XPO - it's a really well designed product... very easy to use etc. and it's evident that they put a huge amount of effort into developing an extremely polished framework there. However, at the same time it's clear that very little of that care and attention was given to how XPO could be used in an n-tier solution until very recently (at the insistence of many customers, myself among them, and they haven't as yet released anything in this regard so I'm still waiting to see what the results will be)...

I'm not shy of pointing out possible improvements, even for very mature frameworks. Whilst often this is simply a result of my lack of knowledge of the frameworks features (in which case usually someone sets me right quick enough, which is ideally what I'm after) I don't think this is the case here.

You're quite right, nHibernate is not the only ORM to incorporate the idea of sessions and, indeed, it's not the only one to make it obligatory (XPO being case in point). This is exactly my frustration though - I think they all do so unnecessarily and, as yet, I've yet to hear a convincing argument to the contrary.

Best Regards,

James Crosswell
Microforge.net LLC
http://www.microforge.net
.

Relevant Pages

  • Re: Finally which ORM tool?
    ... to represent the same state as the server, so the aliasing wouldn't ... between your n-tier application server and client in an pure ADO.NET ... If you don't want to use sessions, use an ORM which isn't session- ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: Finally which ORM tool?
    ... If you don't want to use sessions, use an ORM which isn't session- ... the ORM framework code can rely on sessions being available. ... stay away from such a beast (for the reasons above). ...
    (microsoft.public.dotnet.languages.csharp)
  • Re: Event ID 538 Logon Type 3 NT AUTHORITY/ANONYMOUS LOGON
    ... server for successful anonymous logoff which indicates that these events may ... Client for Microsoft Networks enabled on your server is causing the null ... > In your response, you mentioned 'null sessions'. ... > Computer Browser service is disabled on ...
    (microsoft.public.win2000.security)
  • RE: Terminal server exeeded the maximum number of allowed connections
    ... server, please perform the following steps to see whether other users are ... Remote Desktop connections yours? ... double-click RDP-Tcp in the Connections folder and click the Sessions tab. ... Microsoft CSS Online Newsgroup Support ...
    (microsoft.public.windows.server.sbs)
  • Re: using Terminal server for applications management
    ... You're right, they find that 2 sessions are'nt enough to work, because there are tree to work, and sometime i have to get a session too. ... I have to confess that actually on Windows 2k, they already use terminal services without any troubles, and they dont understand that, because of a migration on windows 2003, they can not use terminal services any more, except because they changed the IT Manager:) ... has any other role, like being a database server, domain controller, exchange server or whatever. ... Having more than 2 administrators working *simultaneously* on a server is in itself a dangerous situation. ...
    (microsoft.public.windows.terminal_services)
Quantcast