Present: Alessandro, Francesco, Kris (minutes), Vito
Excused: Francois, Marc
Francesco and Marc received a mail from Softwired (today) in which they announce a new version coming out soon and which implements many of the features which we asked for: Administration GUI, wildcards for subjects, JDBC interface etc. Francesco will forward the mail to everybody. The asked if we are interested in field-testing it.
Another news item from Marc (on training today) was, that the SmartSocket implementation will be available at the end of the year.
The general opinion was that we have to take our decision based on the evaluation of the official product release rather than a pre-release. Sonic also has a new version (3.0) in beta.
Since the ONLY product which can be seen as operational and stable NOW is SonicMQ, we select it, as it was required in the Milestone Plan. We will order 4 licenses to have a broker with a hot stand-by installed both in SL and PS. The orders will be made separately in SL and PS.
It has to be stressed that this is a preliminary choice as it is a fast-moving technology and we may reevaluate the products in 6-12 months. The investment is not very big as the products are rather inexpensive.
Alessandro explained that if the MOM has to be used in the PS operation next year, a static subscription to Front-Ends from the MOM Agent is not sufficient. If he had to make a static subscription to all subscribable properties this would result in thousands of data items (each property multiplied by the number of PLS lines) to be updated every 2.1 second. This would put an unacceptable load on the relatively slow Front-Ends. (Kris remark: It would be good to make an test to justify this statement and also to test the limits of the MOM approach).
The discussion went on how to implement "temporary subscription" via the MOM. The only approach which we know that it can be easilly implemented is to use a special "admin" topic to notify the MOM Agent about the monitorOn/monitorOff. Kris pointed out that such approach is not sufficient as it cannot be guaranteed that the monitorOff will be notified to the Agent. Vito believes that this is guaranteed by the Java finalize. Kris maintains that the count of clients subscribed to a device/property will became wrong after days or weeks of Agent operation as JVM can crash and network can become temporary unavailable. In his opinion MOM is excellent for loosely coupled systems and many clients and CORBA callback is an adequate solution where subscriptions are sparse. Francesco proposed to introduce periodic re-subscription to cope with the problem of lost monitorOff indication. Alessandro and Francesco will meet and propose a solution.
In the current CMW API the subscription is directed in a static way either to the CORBA implementation or to the MOM implementation. Vito will introduce an environment variable to control this. MOM will be default. Kris proposed to choose dynamically by resolving device name in the integration layer.
Alessandro is worried that he may not be available for a period for 4 weeks in the next 2-month as he has to undergo a knee operation. Therefore the MOM solution has to be rock-solid during this time. He said that one possibility for the PS would be to use CORBA for device/property subscription and MOM for the topic subscription. To be confirmed.
This subject was only briefly discussed due to lack of time. Francesco proposed a public API couple of month ago but we are lacking experience as for it's use. Vito proposed to adopt it as it is and extend it later. Kris said that the public API's shall be stable. It appears that it is not clear what should be the functionality covered by this API (simple pub/sub or shall other facilities as point-to-point, guaranteed delivery etc. be covered as well. Francesco insisted that the semantics of the public CMW MOM API shall be restricted as compared to the general JMS API. We will discuss Public topic API in the next CMW meeting next wednesday.