TOleDBConnection and multithread

mpv · 2012-04-25 12:28:13

Refer to ticket http://synopse.info/fossil/tktview?name=213544b2f5.
The problem is more complex:
Call to TSQLDBConnectionPropertiesThreadSafe.ThreadSafeConnection usually made from inside HTTPserver thread, and corresponding CoInitialize call in HTTPserver thread context.
Call to TSQLDBConnectionPropertiesThreadSafe.Destroy is made from main thread, therefor call to CoUnInitialize is not made from thread in witch CoInitialize called.
As result we have "Missing TOleDBConnection.Destroy call in" in SynOleDB.finalization

The solution is to define event like THttpServerGeneric.OnHTTPThreadTerminate. (OnTerminate is unusable because of Synchronize)

With such type of event a write something like:

procedure MyServer_OnHTTPThreadTerminate(sender: TObject);
begin
  fMyCnnProp.EndCurrentThread;
end;

Arnaud, I sent patched SynCrtSock.pas for you.

ab · 2012-04-25 14:30:36

Nice catch.

I've added a new THttpServerGeneric.OnHttpThreadTerminate event, available to clean-up any process in the thread context, when it is terminated (to call e.g. TSQLDBConnectionPropertiesThreadSafe.EndCurrentThread in order to call CoUnInitialize from thread in which CoInitialize was initialy made).
See http://synopse.info/fossil/info/b2e16aae7d

I guess in this case, the assert(OleDBCoinitialized>0) in SynOleDB.CoUninit is not triggered any more, right?
I've made the assertion message much more explicit, in order to state that there is an error in the thread implementation, and the new THttpServerGeneric.OnHttpThreadTerminate event should be used, if necessary.

Thanks a lot for the feedback!

mpv · 2012-04-25 15:15:56

Yes, now all OK. Thanks!

mpv · 2012-07-06 15:04:34

AB, Hi!
I found some problems in mORMot when use TSQLDBConnectionProperties.GetFields and other database-structure related methods with TSQLDBConnectionPropertiesThreadSafe descendants.
These methods use MainConnection to get database structure, but in multithread (TSQLDBConnectionPropertiesThreadSafe ) it's not good, even with OleDB.
The solution I propose is to make function TSQLDBConnectionProperties.GetMainConnection virtual and override it in

function TSQLDBConnectionPropertiesThreadSafe.GetMainConnection: TSQLDBConnection;
begin
  Result := ThreadSafeConnection;
end;

This will solve problem in easiest way.

I write a ticket for tracking.

ab · 2012-07-06 15:40:23

@mpv
Nice solution.

See http://synopse.info/fossil/info/0bc48ff9a0

畅雨 · 2013-11-02 15:29:04

ad,
I do not use THttpServerGeneric ,only use olednconnection ,how can i free it?
help

code:
...
fDefaultConnectionProperties:=TOleDBMSSQL2012ConnectionProperties.Create('.','database','sa','');
fDefaultConnectionProperties.Execute(sql,param);
freeandnil(fDefaultConnectionProperties) ;
....

When exit application, the process can not be terminated.

Last edited by 畅雨 (2013-11-02 16:40:25)

ab · 2013-11-02 22:32:35

The statement interface should be released before freeing connection properties.

畅雨 · 2013-11-03 01:38:10

Oh，but ，not do it ：(
When exit application, sometime the process can not be terminated, sometime trancing to here：
---->
assert(OleDBCoinitialized>0,'You should call TOleDBConnection.Free from the same '+
'thread which called its Create: i.e. call MyProps.EndCurrentThread from an '+
'THttpServerGeneric.OnHttpThreadTerminate event - see ticket 213544b2f5');
dec(OleDBCoinitialized);
if OleDBCoinitialized=0 then
CoUninitialize;

畅雨 · 2013-11-03 01:47:52

My test code (delphi7):

unit Unit1;

interface

uses
  Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
  Dialogs,synoledb, StdCtrls;

type
  TForm1 = class(TForm)
    Button1: TButton;
    procedure FormCreate(Sender: TObject);
    procedure Button1Click(Sender: TObject);
    procedure FormDestroy(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
    MSSQL2012OLEDB:TOleDBMSSQL2012ConnectionProperties;
  end;

var
  Form1: TForm1;

implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
begin
   MSSQL2012OLEDB:=TOleDBMSSQL2012ConnectionProperties.Create('.','dh1pmip','sa','');
end;

procedure TForm1.Button1Click(Sender: TObject);
begin
  MSSQL2012OLEDB.Execute('select 1 as  aa',[]);
end;

procedure TForm1.FormDestroy(Sender: TObject);
begin
  MSSQL2012OLEDB.Free;
end;

Click button1, run MSSQL2012OLEDB.Execute,
When exit application, the process can not be terminated.

ab · 2013-11-04 18:02:55

I just performed tests for MS SQL Server, with no problem.
I used SQLExpress 2008 R2 via OleDB.
It is now supported by the "15 - External DB performance" sample.
Performance is pretty amazing.
See http://blog.synopse.info/post/2013/11/0 … ing-MS-SQL

Also fixed some issues with the SQL generated by the ORM for index creation.
See http://synopse.info/fossil/info/63b6db715d

mORMot Open Source

#1 2012-04-25 12:28:13

TOleDBConnection and multithread

#2 2012-04-25 14:30:36

Re: TOleDBConnection and multithread

#3 2012-04-25 15:15:56

Re: TOleDBConnection and multithread

#4 2012-07-06 15:04:34

Re: TOleDBConnection and multithread

#5 2012-07-06 15:40:23

Re: TOleDBConnection and multithread

#6 2013-11-02 15:29:04

Re: TOleDBConnection and multithread

#7 2013-11-02 22:32:35

Re: TOleDBConnection and multithread

#8 2013-11-03 01:38:10

Re: TOleDBConnection and multithread

#9 2013-11-03 01:47:52

Re: TOleDBConnection and multithread

#10 2013-11-04 18:02:55

Re: TOleDBConnection and multithread

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