EWS Managed API: PullSubscription - is Unsubscribe call enough?

Question

We are doing some optimization of our app that heavily uses EWS and one point is about cleaning subscriptions that are no longer needed. We are using PullSubscription type so naturally first thing I did was to make sure there is a Unsubscribe method call for each of subscriptions that should be removed.

To my surprise according to Exchange performance counters number of subscriptions after Unsibscribe calls decreases only by several subscriptions not to 0 (for testing purposes I call Unsubscribe for all of open subscriptions). Like we have 200 mailboxes, for each 3 subscriptions (each for different kind of items: emails, appointments, etc.) which equals 600 active subscriptions. And after Unsubscribe calls (for all 600 of them) counters show that only 10 or so subscriptions were removed. If we run our app few times number of subscriptions grows each time.

So does Exchange somehow buffer or delay or do whatever with those subscriptions? Is Unsubscribe call enough or should I do something additional to be sure that subscription is removed and not hanging on server eating resources? Or maybe it is something about config of server and how EWS service works?

Of course EWS documentation is so vocal about it as in most other cases (which means only basic class reference, no possible problems solutions, nothing useful in solving issues) so I hope somebody here will throw me some hints.

Answer 1

You cannot do more than unsubscribe from all subscriptions. Exchange should handle that and discard old subscriptions over time...