Adapter snapshot lifecycle

[rajesh.palanisamy]

Hi,
I just wanted to clarify when the snapshot items will be discarded by the kernel. what is the timeout or lifecycle for it.

My understanding
1. once all active subscriptions for that item is unsubscribed - does it happens the next second or we have a timeout for it
2. explicitly calling the clearSnapshot method.

Thanks
Rajesh

[DarioCrivelli]

Hi Rajesh,
Your understanding is correct, but point 1 deserves some clarifications.
In general, when all subscriptions for an item are terminated through unsubscriptions, the subscription is no longer maintained by the Server, which implies three consequences:

• unsubscribe() is invoked to the Data Adapter;
• the item snapshot is discarded;
• upon the next subscription, subscribe() will be invoked to the Data Adapter.

This is done immediately, with no timeout.
However, if a session is terminated without explicit unsubscriptions of the item, a timeout is applied to each of these items, which can be configured through the <subscription_timeout_millis> element.
Note that, in some cases, a timeout is applied to an unresponsive session before stating that it is terminated (see <session_timeout_millis> and <session_recovery_millis>). In this case, the longer of the two timeouts is applied to the items.

[rajesh.palanisamy]

Thank you , I am clear now.