How to correctly unsubscribe from EventStoreStreamCatchUpSubscription

EventStoreDB
#1

I am trying to unsubscribe from the stream using subscription handler Stop method:

EventStoreCatchUpSubscription subscription = null;

        subscription = connection.SubscribeToStreamFrom(stream, position, false, (s, e) =>

            {

               if (IsTheOne(e))

               {

                   DoSomething(e);

                   try {

                      subscription.Stop(TimeSpan.FromSeconds(30));

                   } catch (Exception exc) {

                       Log(exc);

                   }

               }

            });

But every time after the wait timer elapses in Stop method i receive ‘System.TimeoutException: Couldn’t stop EventStoreStreamCatchUpSubscription in time’. What am I doing wrong?

#2

If you call it from outside of your handler does it stop properly? Just curious.

Greg

#3

Also do you know if you’re in the “live” subscription part of your stream or reading history?

#4

yes, that was it. Transferred Stop part to another thread, and it works now. Don’t know if this is ok.

EventStoreCatchUpSubscription subscription = null;

        subscription = connection.SubscribeToStreamFrom(stream, position, false, (s, e) =>

            {

               if (IsTheOne(e))

               {

                   DoSomething(e);

                   Task.Factory.StartNew(() => {

                                try {

                                    subscription.Stop(TimeSpan.FromSeconds(10));

                                } catch (TimeoutException exc) {

                                    log.Error(exc);

                                }});

               }

            });
#5

My guess is its waiting on your handler to finish to actually stop :slight_smile:

#6

yes, I am in a live subscription. I simply wait for the answer to the command I’ve sent.

#7

The relevant code is here: https://github.com/EventStore/EventStore/blob/dev/src/EventStore.ClientAPI/EventStoreCatchUpSubscription.cs#L141

And yes its waiting for your handler to end. I will add an overload that marks stop but does not block on it that you can use in your handler.

Cheers,

Greg

#8

yes, that would be much better.

#9

Done. https://github.com/EventStore/EventStore/pull/153

#10

cool, thanks. cloning…

#11

returning to that question.

Is this really safe to stop the subscription from the handler? Won’t there be a situation when the subscription variable will be null? I mean the situation when handler will be called earlier than the SubscribeToStreamFrom will return.

EventStoreCatchUpSubscription subscription = null;

        subscription = connection.SubscribeToStreamFrom(stream, position, false, (s, e) =>

            {

               if (IsTheOne(e))

               {

                   DoSomething(e);

                   subscription.Stop();

               }

            });
#12

discard this question :slight_smile: just saw the EventStoreCatchUpSubscription is passed to the handler… don’t know how I missed that :slight_smile:

#13

what about disconnecting from catch-up mode (reading history)? Stop methods seems to work only for live subscription.

#14

It appears a check got taken out in a refactor somewhere along the way. This PR should resolve the issue.

https://github.com/EventStore/EventStore/pull/160

Someone else should approve it quickly to dev (we generally don’t self accept prs :)). Feel free to pull it and test though.

Cheers,

Greg

#15

Doesn’t build :). _stoped is private and cannot be accessed in inherited class.

#16

check now not sure how half the change was there.

#17

still requires some changes:

  • wrong loop condition, should be - while (!done && !_stop) :slight_smile:

  • this should be also applied for EventStoreAllCatchUpSubscription class as well, not only EventStoreStreamCatchUpSubscription

R.

#18

Hi Raimondas,

See commit 84ad492 - this should now be doing what you need.

Cheers,

James

#19

Great, thanks. Will check it.