Are there tools to help upgrade from DO 3.9 to 4.x? (at a minimum the persistence layer). Some documentation about the how to convert DO 3.9 features to 4.x (like DataService, sample how to implement RuntimeService, sample how to implement Lucene support, sample how to implement user/roles (and permissions).

When i look at the examples all i can find are simple apps, same level as tests. I like to see an example with some business logic, reporting scenario's, UI paging / filtering large resultsets (with many tables involved), login/logout, exception logging in database (rollbacked transaction issues), best practices to upgrade large application (maybe separate upgrade app), etc....

Thanks

asked Nov 20 '10 at 05:34

Marco's gravatar image

Marco
22161618

edited Nov 20 '10 at 05:35


2 Answers:

Are there tools to help upgrade from DO 3.9 to 4.x?

Unfortunately, no.

Some documentation about the how to convert DO 3.9 features to 4.x

Again, no. And, frankly speaking, I fear we have no time on writing this guide.

But I'm certainly ready to answer on particular questions here.

like DataService

The most close analogue is Session.Services - see the description and examples in Manual.

sample how to implement RuntimeService

Currently we don't ship any close analogue, but provide more generic API for this: you must implement IModule in some of types you register. Its OnBuilt(Domain domain) method allows you to create a dedicated Session and thread for your own analogue of runtime service(s).

Also, you can subscribe to Domain.SessionOpen event there to intercept Session-related events.

sample how to implement Lucene support

We don't support Lucene; moreover, actually we're quite rarely asked about its support. So currently implementation of this feature isn't scheduled.

sample how to implement user/roles (and permissions)

Access control API will be available pretty soon as part of Xtensive.Practices (new namespace in v4.4 containing all optional stuff). Hopefully, by the end of this year in beta.

Btw, if you need something simple, you can start with your own model. Just create your own User and Role types and implement your own authentication, but leave ACLs and permission checks API to us. There is a big chance it will be available when you'll really need this.

I can add that likely we won't provide our own authentication API in this version. We'll just provide a way to say who's current user - something like this:

var accessControl = session.Services.Demand<AccessControl>();
accessControl.User = authenticatedUser;
var readPermission = accessControl.GetPermission("ReadObject");
accessControl.Demand(readPermission, someEntity);
var query =
  from o in session.Query.All<Order>()
  where accessControl.HasPermission(readPermission, o)
  where ...
  select o;

Remember this is just an example. Actual API should be different.

When i look at the examples all i can find are simple apps, same level as tests.

That's true - we tried to build simpler examples with this version - they're easier to understand for newcomers. Likely, we'll publish some complex examples later, but actually, I don't see a real need for this. Our current goal is to describe all the features - their practical implementation is actually pretty obvious.

Btw, if you're interested in complex BLL, see AuditAndOpenGenericsTest in Xtensive.Storage.Manual project (btw, v4.4 will contain it; currently you can view its version from v4.2 in Google Code).

I like to see an example with some business logic

Hmm, just checked and discovered we really never override event-like methods of Entity to show reaction to various events (removal, field value change, etc.). So we'll fix this.

Btw, AuditAndOpenGenericsTest gives some impression on what can be done: nearly any Entity-level event now has its Session-level analogue, and this relies on the second option to implement the audit transparently.

reporting scenario's

There is nothing special: you can use either our own LINQ query translator for reporting (we prefer this option), or rely completely on database structures and some third-party reporting engine.

UI paging

It's pretty easy with LINQ - .Skip(...) and .Take(...) methods solve the most important part in this case. Everything else (e.g. some high-level wrappers) is up to you.

See AspNetMvcSample2 in Sandbox projects - it shows paging over ~ 100K of entities. But there is really nothing special.

filtering large resultsets (with many tables involved)

Again, LINQ itself should work perfectly here:

  • Our goal is to translate nearly anything you pass
  • Your goal is to build filtering expression. There are lots of examples on this on the web.

login/logout

This isn't what we're going to implement soon - mainly, because this is pretty specific to a particular application. We thought about implementing membership provider for DO, but finally found this not so attractive: in any particular case this is pretty easy (~ 1 day of work), but since we must implement this in general case, it will be more complex, and moreover, we'll need to document and support this. So we decided to postpone this.

This explains why we don't implement other particular solutions, and that's why we extract Xtensive.Practices project:

  • Obviously, we can't implement integrated solution for any particular problem developers face;
  • But there are some common ones. We're implementing them in generic way, but now we always take into account maintainance and documentation costs. So if problem is really complex and common, there is a big chance it will be solved by us (e.g. ACLs and caching - in both cases the API we provide is good enough to implement them on the top of it, but we're anyway working on support of these particular scenarios), but if it's pretty simple (e.g. login/logout), we avoid providing integrated support for it.

exception logging in database

That's easy as 1-2-3: as far as I can judge, you should just catch it and log :) If this is done in the same transaction, nothing will be committed if the transaction will be rolled back because of this. Otherwise (e.g. if you're using separate Session) the error report will be persisted anyway.

rollbacked transaction issues

If you mean deadlocks and version conflicts, there are really no samples about this. Moreover, currently DO is incapable of reprocessing transactional method calls on deadlocks (but this will be done almost instantly of few users will vote for this feature here), so there is really nothing special. You should do this as you'd do this normally.

E.g. that's pretty easy with ASP.NET MVC; regular ASP.NET requires some hacks like we used in v3.X; WPF applications need either our own automatic transaction reprocessing or some custom infrastructure for this (e.g. any data fetch attempt must be executed as delegate passed to a special method providing transaction + reprocessing for this).

best practices to upgrade large application (maybe separate upgrade app), etc...

No, we don't recommend you to use a separate upgrade app. I'd recommend you to use the approach used by us in nearly all the samples - i.e. just build the Domain. If you'll need something more complex (e.g. first build it in Validate mode, and then, if user confirms this - in Perform mode), it's normally pretty easy to modify the code in accordance with your needs (e.g. few lines in described case).

But the topic seems really poorly covered, so I'll write a dedicated post about this soon.

Hopefully, this will help.

answered Nov 22 '10 at 17:05

Alex%20Yakunin's gravatar image

Alex Yakunin
29714412

Thanks for your answer, but some comments:

upgrade 3.9 to 4.0 not available

But any work in progress to create a DO datamodel from an existing database?

Exception logging, That's easy as 1-2-3: as far as I can judge

This is exactly my point, it seems easy, but if you don't open a new session (not a new transaction??) nothing is logged. An example is welcome or another scenario: import many records records, continue and log failures, without rollback of the complete import process.

Samples

Maybe you could convert the Petshop sample and show all of the features of DO.

Thanks Marco

answered Nov 23 '10 at 03:52

Marco's gravatar image

Marco
22161618

If i can join into this discussion, for point "...DO datamodel from an existing database?" I am working on T4 Active Record tool for DO4 to generate DO4 model classes from existing database. Just for now it was frozen from my side (i have too much work on other projects), but want to publish some beta in the end of this year (maybe as Christmas gift).

(Nov 23 '10 at 04:21) Peter Ĺ ulek Peter%20%C5%A0ulek's gravatar image
1

But any work in progress to create a DO datamodel from an existing database?

We ourselves don't work on such tool, although we know there are at least two early implementations of something similar. So likely, we'll try to get an agreement to use the code of one of such tools as base for "official" one.

But this should happen only after NY.

(Nov 23 '10 at 04:31) Alex Yakunin Alex%20Yakunin's gravatar image

but if you don't open a new session (not a new transaction??) nothing is logged.

No, that's not correct: if you add log records in the same transaction, obviously, only logs of successful transactions will be there, and nothing will be stored of these ones that failed.

(Nov 23 '10 at 04:34) Alex Yakunin Alex%20Yakunin's gravatar image

import many records records, continue and log failures, without rollback of the complete import process.

Ah, clear. You mean, in some cases you must avoid rolling back of the outermost transaction when exception occurs?

If so, the best option is to use transactional batched import.

(Nov 23 '10 at 04:56) Alex Yakunin Alex%20Yakunin's gravatar image

Example batch import code:

int batchSize = 16;
var items = ...; // IEnumerable of large set of items to import
foreach (var batch = items.Batch(batchSize)) {
  var excludedItems = new HashSet<TItem>();

  Func<bool> batchImporter = () => {
    using (var tx = session.OpenTransaction()) {
      foreach (var item in batch) {
        try {
          ImportItem(session, item);
        }
(Nov 23 '10 at 04:57) Alex Yakunin Alex%20Yakunin's gravatar image

Continuing:

        catch {
          Log.Error(e); // Btw, try using our logging framework, it's cool :)
          excludedItems.Add(item);
          return false;
        }
      }
      tx.Commit();
    }
    return true;
  };

  while (!batchImporter.Invoke()) {
    // Nothing to do, we must just retry
  };
}
(Nov 23 '10 at 04:57) Alex Yakunin Alex%20Yakunin's gravatar image

Maybe you could convert the Petshop sample and show all of the features of DO.

We'll publish more modern one for ASP.NET MVC (hopefully, ~ in February). PetShop doesn't use AJAX and is based on regular ASP.NET. Also, it is almost useless as the application itself. We'd like to publish something that people reaslly can use as basis - i.e. extend and ship it.

(Nov 23 '10 at 05:01) Alex Yakunin Alex%20Yakunin's gravatar image
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Asked: Nov 20 '10 at 05:34

Seen: 3,610 times

Last updated: Nov 23 '10 at 05:03

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