mORMot Open Source

Unfortunately, this wouldn't work for us.

We need to control the database transaction on the server-side.

We have multiple mormot servers running in parallel (AWS AutoScaling) and receiving the load from a Elastic Load Balancer, so, client requests can hit different servers.

The problem that we are trying to solve is this: A client made a destructive call to the server (Insert/Delete/Update) but the connection was interrupted (client timeout, etc.). In that case, the client would assume that none of the changes are applyed on the database, so, we would like to rollback the transaction if anything goes wrong.

that will work, but, I will have more than a thousand channels with potentialy more than 5k callbacks, it would be slow, don't you think? A hashlist would be much more efficient.

Not sure, but will end up in the same problem, I think.

Thanks Daniel,

I was able to change the headers by overriding the InternalRequest on TSQLHttpClient.

function InternalRequest(const url, method: RawUTF8; var Header, Data, DataType: RawUTF8): Int64Rec; override;

The major problem is that the load balancer (AWS ELB) will send the request to any of the servers and it is not predictable. So, I can't rely on any in-memory information/session on the server side.

This server will serve a ton of clients with a low usage per client, so, I'm using sicPerThread.

In this case, I want to serialize the ClientDataSet Data and Delta properties.

The problem with DatasetToJSON danielkuettner is the JSON, in first place, I would prefer something more optimized for speed. The other problem is that I don't have a method that does the inverse. JSONToClientDataSet dose'n work because of the blobs base64 encoding, as stated on the first post.

I was able to make it work with SynDBDataset. Thanks.

Thank you, I will take a look in SynDBRemote.

still have the same problem:

  produto.FillPrepareMany(DatabaseServer, 'Dest.Codigo=?', [], ['1000']);

Error: 'no such column: Dest.A.Codigo'

I had this same problem today! It's unfortunate.

I solved getting the type of the "First" method.

Rtti.GetType(ObjectList.ClassInfo).GetMethod('First').ReturnType

I know, it's very strange. But so far I have not found a better way.

Today I ran the same software again and got some new errors. I have the latest mORMot version (updated-to:   21a1dd69da94b5736f090f533681abeefcb8460b 2013-07-29 16:18:35 UTC)

When running the test with 4 threads i'm getting this message:
{
"ErrorCode": 408
"ErrorText": "Request Timeout"
}

Thanks

Only found this option. Is that correct?

TSQLDBSQLite3Connection(Props.MainConnection).DB.Backup('teste.bkp');

Is there any way to restore this backup in the framework?

It has some class that provides a method similar to BackupGz with compression?

I'll wait for the new results.

Something very strange happened here.

I set up an environment for remote debugging with Delphi 6 and Wine to try to identify this problem (Never thought it would work, but it works! ).
I removed all of the mORMot units and the application continued not starting.

I removed all the code from the project, it was just the Form. And nothing.
I recreated the project from scratch, including the same things of the previous design. And it worked!

I have no idea what happened.

Sorry. I thought was in last version. But there were some read-only sources (my fault).  When performing "Fossil Update" he did not warned me. I thought it was updated, but it was not.

I'm trying to do some tests to compare the performance of SQLite vs Firebird Embedded.

I wish the two worked with the same kind of synchronization.
According to this article (http://blog.synopse.info/post/2013/06/1 … cking-mode) I should use this:

better Security:
Client.Server.DB.LockingMode := lmExclusive;
Client.Server.DB.Synchronous := smFull;

best Performance
Client.Server.DB.LockingMode := lmNormal;
Client.Server.DB.Synchronous := smOff;

Is that right?

The first problem is that I have not found the property "DB.LockingMode".

Have any way to set the framework to work the same way with the two databases? To be a fair test!

thank you very much!

I have a problem. What am I doing wrong?

I have this code (Using OmniThread Library):

procedure TForm1.FormCreate(Sender: TObject);
begin
  Model := CreateSampleModel;
  Database := TSQLRestServerDB.Create(Model, ChangeFileExt(paramstr(0),'.db3'));
  TSQLRestServerDB(Database).CreateMissingTables(0);
end;

procedure TForm1.AddValues;
var Rec: TSQLSampleRecord;
  i: Integer;
begin
  for i:=0 to 100 do
  begin
      Rec := TSQLSampleRecord.Create;
    try
      Rec.Name := GetCurrentThreadId().ToString + GetCurrentTime.ToString + i.Tostring;
      Rec.Question := StringToUTF8('TESTE - '+GetCurrentThreadId().ToString + GetCurrentTime.ToString + ' Loop:'+i.ToString);
      if Database.Add(Rec,true)=0 then
        raise exception.create('Error adding the data');
    finally
      Rec.Free;
    end;
  end;
end;

procedure TForm1.BtnParallelClick(Sender: TObject);
var
  i: Integer;
begin
  for i := 0 to 20 do
    Parallel.Async(AddValues);
end;

Sometimes when running BtnParallelClick I encounter this error: ESQLite3Exception with message 'database is locked';

Thank you Arnaud. I'll test.

That is ok. I agree.

Certainly any of these methods would already be great. Some of them already exist?
How I have not found this method in class TSQLHttpClient, I deduce not!

I like the implementation with generics, but as it only works in the newer versions of Delphi is not very useful for us.
An even simpler implementation without generics, might look like:

Client.GetService(ICalculator,Calculator);

with generics:

Calculator := Client.GetService<ICalculator>;

Sometimes I do not know if you're for or against my implementation.  Let's try to clarify.

I think there may be cases where the client has access to all the classes available on the server. But that's okay. Let's say that the model (SQLModel) client has only a part of the classes that are on the server model. This will slightly change my implementation. But it is still possible.

I do not understand what you mean by "Use case of the TSQLModel instance is to be defined in a given object context.";

My implementation does not differ so much from the implementation you used in the "CreateSampleModel". However, the "CreateSampleModel" has only one entity. In case you have multiple entities the implementation would be slightly different, I guess. And if not, the unit SampleData.pas (Ex 04) would have to know all the entities.

When you say that my implementation will add a dependency, you mean that all entities will depend on another unit, in my case, EntidadesPublicas.pas?
Regard this entities will have to be shared between several projects. Create a dependency of another unit, also shared, is a problem?

What would you change in my implementation?
You would drive EntidadesPublicas.pas know all the entities and create the model from them?

I'm sorry, but this demo is very confusing.

Got it. I'm thinking of a way to facilitate the use of interfaces for developers. But not reached a conclusion yet. Imagine that developers who make the server are not the same that will implement the client.

Another thing. I'm not pleased about having to use an identifier of type String to get the service. Like that:

var
  Calculator: ICalculator;
begin
  Client.Services['Calculator'].Get(Calculator);
end;

It would not be possible to have something like this?

var
  Calculator: ICalculator;
begin
  Client.GetService(Calculator);
end;

Maybe we can get the identifier via RTTI, what do you think?