Unexpected update for item - why is it necessary to log it as WARN?

pluczak

Hi,
judging by Mone's post which I found here:
http://http://www.lightstreamer.com/vb/showthread.php?t=323
the message

< WARN> Unexpected update for item xyz

is displayed when Lightstreamer is provided with an update for an item which has not been subscribed to.
Given the fact, that "subscribtion" in this case means "presence of a client", I assume that this warning will be generated each time there is no actual client trying to get that particular xyz item. Now, two quick questions:
1. do I understand this subscription mechanism correctly?
2. if the answer to question 1. is "yes" then why would a lack of clients be reported as a WARN? After all, it's possible that no one is currently visiting my site (I use HTML clients along with java adapters), which is perefctly ok. Why would I need to be warned about that?
Thanks

Giuseppe Corti

When no more clients are still subscribing for an item Lightstreamer server send a unsubscribe call for that item to the appropriate Data Adapter; since then no updates for that item will be expected.

In fact, the Data Adapter should not interact with the server as if it were a bus, sending data as a continuous flow, but must interact with the server in response to subscribe and unsubscribe requests.
When a Data Adapter receives a subscribe request it starts to send possibly snapshots and then all the updates, when it receives an unsubscribe request it must stops sending updates, and be ready to repeat the cycle when a new subscribe request arrives.