Can not make replication to work

larand54 · 2023-10-05 10:04:15

Only when the master server is restarted the sync works but only once.

In the slave log I can see the following repeated five times:

2023-10-05 09:24:14.640	Debug	    mormot.rest.sqlite3.TRestServerDB(035da1e0) RecordVersionSynchronizeSlaveStart(TORMUser) current=19 Subscribe(036ec488)
2023-10-05 09:24:14.640	Enter	    mormot.soa.client.TServiceFactoryClient(036fac98).InternalInvoke IServiceRecordVersion.Subscribe("User",19,1) 
2023-10-05 09:24:14.640	Enter	       mormot.rest.http.client.TRestHttpClientWebsockets(03d93730).InternalUri POST
2023-10-05 09:24:14.640	Trace	          mormot.rest.http.client.TRestHttpClientWebsockets(03d93730) InternalRequest POST calling THttpClientWebSockets(03d939a0).Request
2023-10-05 09:24:14.640	Client	          mormot.rest.http.client.TRestHttpClientWebsockets(03d93730) POST DHSSync/ServiceRecordVersion.Subscribe status=200 len=18 state=1
2023-10-05 09:24:14.640	Leave	       00.003.082
2023-10-05 09:24:14.640	Service return	       mormot.soa.client.TServiceFactoryClient(036fac98) {"result":[false]}

and then I get an error:

2023-10-05 09:24:14.704	Error	    mormot.rest.sqlite3.TRestServerDB(035da1e0) RecordVersionSynchronizeSlaveStart(TORMUser): retry failure

The code in the slave looks like this:

procedure TForm5.btnSynchronizeClick(Sender: TObject);
  function setUpSyncServer: TRestServerDB;
  begin
    result := TSQLRestServerDB.Create(CreateSyncModel, ChangeFileExt(Executable.ProgramFileName, '.db'));
    result.DB.Synchronous := smOff;
    result.DB.LockingMode := lmNormal;
    result.Server.CreateMissingTables;
  end;


begin
  if not fSyncRunning then
  begin
    btnSynchronize.Caption := 'Stopp Synk';
    fSyncServer := SetUpSyncServer;
    fHttpClientSync := TRestHttpClientWebSockets.Create('127.0.0.1', '8888', CreateSyncModel);

    fSyncServer.RecordVersionSynchronizeSlaveStart(TORMUser, fHttpClientSync);
    fSyncRunning := true;
  end
  else
  begin
    btnSynchronize.Caption := 'Synka';
    fSyncServer.RecordVersionSynchronizeSlaveStop(TORMUser);
    freeAndNil(fSyncServer);
    freeAndNil(fHttpClientSync);
    fSyncRunning := false;
  end;

end;

The master part:

function setUpOrmSyncServer: TRestServerDB;
begin
  result := TRestServerDB.Create(CreateSyncModel, ChangeFileExt(Executable.ProgramFileName, '.db'));
  result.DB.LockingMode := lmNormal;
end;

begin
  OrmSyncServer := setUpOrmSyncServer;
  HttpSyncServer := TRestHttpServer.Create('8888', [OrmSyncServer], '+', UseBidirSocket,4 );
  OrmSyncServer.RecordVersionSynchronizeMasterStart;

So I just wonder, What am I missing?

larand54 · 2023-10-13 11:14:35

No answer in a week, I hoped to find some anwer here at least a comment if some necessary information is missing.
I tried to find a solution myself and I feel that I've done what is needed but in spit of that, no success.
I don't believe that this function is incomplete or not functional in mORMot2 but it looks so to me.

Last edited by larand54 (2023-10-13 11:20:58)

ab · 2023-10-13 15:21:38

With such partial code, we can't reproduce your problem.

Take a look at the regression tests, you will see how master/slave replication is supposed to be used.
See TestMasterSlaveRecordVersion() procedure in
https://github.com/synopse/mORMot2/blob … 7C1-L627C1

larand54 · 2023-10-21 09:44:53

Hello ab,
I've already checked out that code and I did a new attempt with a small testproject but still fail.
I have this project available as a zip-file but I don't find any way to share that. PasteBin doesn't seem to to be used with anything but sourcefiles.
Any idea how I can share this file?

I have the project on GITLAB if it could work?
https://gitlab.com/GIT-Testing/test_mor … cation.git

I made a small program that more or less copies the code you have in your test suite.

https://paste.ee/p/cZ9sA

That code works but the difference is that I don't use services here. When simulating changes in the master table I do it directly through the TRestServerDB instance.

But in the real world I need to use services and then I need 2 different http-channels, one for update the table on the master and one for the replication.
And this case don't work for me. See the the GITLAB-project above.
I'm sure that I have misunderstood how to do this correct but I'm also sure it must be someone, that have a working solution of a similar system like mine, that could see what I've done wrong or..?

Otherwise I have to develop a compleatly different solution on my own :-(
Please help.

Last edited by larand54 (2023-11-02 10:54:01)

larand54 · 2023-11-02 10:59:32

Please see my updated reply above.

It seems that it only works once after that I erase the user table first and then start the slave.
The data is copied from master to the slave just after the call:

fSlave.RecordVersionSynchronizeSlaveStart(TOrmUser, fMasterClient, nil);

But not after.

Very strange or...?

Last edited by larand54 (2023-11-02 12:58:49)

larand54 · 2023-11-06 12:32:59

I have another version written for Lazarus if that could be easier for someone to checkout.
https://gitlab.com/GIT-Testing/mormot-r … th-lazarus

This version works as bad as any other of my attempts to find a working solution.

Looks that it is not possible to have the real-time sync with this library.
//LG

ab · 2023-11-07 08:19:25

Sorry I was not able to find time yet to look into this issue.

mORMot Open Source

#1 2023-10-05 10:04:15

Can not make replication to work

#2 2023-10-13 11:14:35

Re: Can not make replication to work

#3 2023-10-13 15:21:38

Re: Can not make replication to work

#4 2023-10-21 09:44:53

Re: Can not make replication to work

#5 2023-11-02 10:59:32

Re: Can not make replication to work

#6 2023-11-06 12:32:59

Re: Can not make replication to work

#7 2023-11-07 08:19:25

Re: Can not make replication to work

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