0 Replies Latest reply on Mar 4, 2004 9:26 AM by DevConUser NameToUpdate

    Web Services API FAQ

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      IIAPI Web Services FAQs

      Updated: 3/10/2004

      Questions:

      1: Should a client connect to any IMpact Manager cell before
      subscribing?
      2: Is there any way to know what the selector entry actually means so
      that the client can subscribe to that selector?
      3: What happens to the events when a polling client does not pull its
      messages from the server?
      4: Does the IMWS server provide guaranteed message delivery?
      5: What happens when a pub/sub client crashes without unsubscribing
      itself from the IMWS server?
      6: What happens to subscriptions when the server process crashes and
      re-starts?
      7: What happens to Impact Manager connections after the server crashes
      and re-starts?
      8: How does a client know about the Impact Manager in the case of
      subscribe pub/poll?
      9: Why does a client "Read time out" when it tried to fetch the query
      count?
      10: Can multiple clients connect to same Impact Manager?
      11: Can multiple clients connect to different Impact Manager cells?
      12: How does a client know about the cells that can to accessed via the
      IMWS server?
      13: What is WSCELL?
      14: Where is the WSCELL configuration?
      15: Can there be multiple IMWS server processes running on a box?
      16: Can multiple IMWS server processes share the same config, selector
      and trace files?
      17: What does the server admin have to do to create multiple WSCELL
      entries in the mcell.dir file and share the filel between multiple IMWS
      servers?
      18: Why does the mposter fail when sending events to WSCELL of the IMWS server?
      19: How many services can I run in my server?
      20: How can I chose to listen to one type of events and not the other?
      21: what is the build date for the web service API 1.1?


      Answers:


      1: Should a client connect to any IMpact Manager cell before
      subscribing?

      No. Subscribing to a selector does not require connection.

      2: Is there any way to know what the selector entry actually means so
      that the client can subscribe to that selector?

      No. A client can view the selector names only. It is recommended that
      the selector names are self-explanatory e.g "Security Events"

      3: What happens to the events when a polling client does not pull its
      messages from the server?

      The IMWS server maintains a limited number of events queued for a
      polling client. This number is configured by the server admin. The queue
      uses the "First Arrived Message" algorithm to replace an old event with
      the latest event.

      4: Does the IMWS server provide guaranteed message delivery?

      No, IMWS server does not provide a guaranteed message delivery.

      5: What happens when a pub/sub client crashes without unsubscribing
      itself from the IMWS server?

      The subscription is not removed from the server subscription table. The
      server will try to send message to that client with failure. There is no
      configuration to specify automatic unsubscribe after certain number of
      tries. The server does not persist any event that cannot be delivered to
      the client.

      6: What happens to subscriptions when the server process crashes and
      re-starts?

      All of the subscriptions are lost. Clients are required to re-subscribe
      if they get an "Client not subscribed" exception.

      7: What happens to Impact Manager connections after the server crashes
      and re-starts?

      They are lost and clients may get errors when they try to access Impact
      Manager operations using the old connection IDs.

      8: How does a client know about the Impact Manager in the case of
      subscribe pub/poll?

      The Impact Manager information may be in the event. In the case of
      modified events, this is not guaranteed.
      9: Why does a client "Read time out" when it tried to fetch the query
      count?

      Getting query count can take a while. In this case it is recommended
      that the client increase the value of its Read Time out HTTP parameter.

      10: Can multiple clients connect to same Impact Manager?

      Yes, multiple clients can connect to the same Impact Manager.

      11: Can multiple clients connect to different Impact Manager cells?

      Yes, multiple clients can connect to different Impact Manager cells.

      12: How does a client know about the cells that can to accessed via the
      IMWS server?

      A client can perform the getCellInfo operation to get a list of cells it
      can communicate with via the IMWS server.

      13: What is WSCELL?

      WSCELL is the default name of the message listener in the IMWS server
      that receives events and data from Impact Manager cells.

      14: Where is the WSCELL configuration?

      WSCELL configuration is in the mcell/mcell.dir file by default. The
      default port number that it binds on is 9999.

      15: Can there be multiple IMWS server processes running on a box?

      Yes, multiple IMWS server processes can be running on the same box
      provided they listen on different port numbers. The config for the IMWS
      server port number is in server/servercfg.xml file.

      16: Can multiple IMWS server processes share the same config, selector
      and trace files?

      Yes, they can share the files provided each process is started with a
      unique WSCELL information.

      17: What does the server admin have to do to create multiple WSCELL
      entries in the mcell.dir file and share the filel between multiple IMWS
      servers?

      The server admin must create different entries for e.g WSCELL, WSCELL1
      and assign unique port numbers for each of the entries. The admin is
      also responsible for specifying unique, unused WSCELL entry during the
      server start-up.

      18: Why does the mposter fail when sending events to WSCELL of the IMWS server?

      The WSCELL starts after the first client subscription. If the mposter
      failed to send an event, then it means that there is no subscription to
      that server yet.


      19: How many services can I run in my server?

      It's depend on the resource of your server. Generally you would want to run 1 service per server for performance purpose. You can chose to run multiple services on difference servers for scalability or for high availability. Each of these services can also handle difference events for load balancing.



      20: How can I chose to listen to one type of events and not the other?

      By subscribe to difference "selector type" or event type as setup by the service administrator. The service administrator are the only one that able to change the "selector types". The "selector type" cannot be change dynamically.

      21: what is the build date for the web service API 1.1?

      The build date for the WS release 1.1 is Feb 14th.