mORMot Open Source

Kabiri

Member

Registered: 2024-06-22

Posts: 63

mORMot + PostgreSQL: "lost synchronization with server" when switching

I'm using mORMot with PostgreSQL, and I suddenly started getting this error:

Project Vi.exe raised exception class ESqlDBPostgres with message:
TSqlDBPostgresLib Exec failed:
[lost synchronization with server: got message type "lost synchronization with server: got message type"]

After this error occurs, the application can no longer connect to the database unless restarted.

Here is how I initialize the connection:

Model := CreateViModel;
DBProps := TSqlDBPostgresConnectionProperties.Create(
  Host, DBName, DBUser, DBPass
);

DBProps.UseCache := False;
DBProps.ReconnectAfterConnectionError := True;

VirtualTableExternalRegister(Model, TOrmTenant, DBProps);
...

Additional details:

The issue seems to happen when rapidly switching between menus in the client (HTMX-based UI).
It looks like multiple concurrent requests may be involved.
After the error, even reconnection does not recover properly.

Questions:

Could this be related to connection reuse or thread safety in mORMot?
Should I be using a connection pool or per-thread connection instead?
Is there a known issue with PostgreSQL driver synchronization in such scenarios?

Any guidance or similar experiences would be appreciated.

Last edited by Kabiri (Yesterday 07:24:36)

ab

Administrator

From: France

Registered: 2010-06-21

Posts: 15,436

Website

Re: mORMot + PostgreSQL: "lost synchronization with server" when switching

If I understand correctly https://www.postgresql.org/message-id/1 … nabble.com
it sounds like the server closed the connection due to too big/slow request.
Look at the request itself, and the full error message.

It may be more tied to the request and server itself that with mORMot.

There is a per-thread connection pool in mORMot.
So nothing is to be configured here.
Just don't create too many threads in your code.

Kabiri

Member

Registered: 2024-06-22

Posts: 63

Re: mORMot + PostgreSQL: "lost synchronization with server" when switching

I was using PostgreSQL 17.6-2. I’ll upgrade to PostgreSQL 18.3-2 and test it.
Maybe the issue was related to this: https://www.postgresql.org/message-id/2 … .pgh.pa.us

Kabiri

Member

Registered: 2024-06-22

Posts: 63

Re: mORMot + PostgreSQL: "lost synchronization with server" when switching

@ab
I updated it and everything was working fine.
After some time—without rapidly switching between menus and without any errors—everything stopped working.

The application reaches this line but never returns from it:

u := TOrmUser.Create;
try
  if not Self.Server.Orm.Retrieve('Email=?',[],[Email],u) then

Kabiri

Member

Registered: 2024-06-22

Posts: 63

Re: mORMot + PostgreSQL: "lost synchronization with server" when switching

Isn’t there any solution?
It’s really frustrating. Right now, even during testing with no users, it keeps getting stuck and I have to restart the service. What should I do when there are many users?