Subscribing to a stream before it is created

EventStoreDB
1

Hi all,

I’m in a situation where I am writing to a stream for all user events but have projections enabled so a stream is created per user id. If a new user is added to the system hence a stream for that user doesn’t exist before I write the first
event, what would happen if I subscribed to that non-existent stream—I need to wait for an event to be written to the new users stream before returning to the caller, is this possible?

Any help appreciated.

Kind regards

Sean.

2

Sean,

I hit the same problem and as far as I know (happy to be wrong) the stream has to be there.

My “ConnectToSubscription” method is like this:

        try
        {
            await connectToPersistentSubscriptionAsync();
        }
        catch(Exception e)
        {
            if (e.InnerException != null && e.InnerException.Message == "Subscription not found")
            {
                //Create the Group
                await this.CreatePersistentSubscriptionFromBeginningAsync(stream, groupName);

                await connectToPersistentSubscriptionAsync();
            }
            else
            {
                throw;
            }
        }

``

3

What kind of subscription?

4

Hi,

Probably a persistent subscripting, although I'm looking at a cachup, so any advice would be appreciated.
Kind regards
Sean.

5

For either you should be able to just set metadata on the original
stream (eg set {foo : bar} etc and they should work. I believe catchup
can work without this (will retry) but would need to test