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  1. #1
    Member
    Join Date
    Mar 2012
    Location
    Frankfurt am Main
    Posts
    7

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

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

  2. #2
    Administrator
    Join Date
    Feb 2012
    Location
    Milano
    Posts
    190
    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.

 

 

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