+1 to go with Greenwich time, or provide a option to turn it on when needed.
Counter would not work either as there can be some time between when event is created and receiver received it. I think we need to live with time stamp. If time accuracy is critical users should sync clocks of all machines with NTP. --Srinath On Wed, Nov 13, 2013 at 5:30 PM, Maninda Edirisooriya <[email protected]>wrote: > What about using the Greenwich time with the existing timestamp? When > there is a timezone critical solution, Greenwich time can be used as it is > the same. > > Anyway in practice I don't think timestamp is the best way to order the > messages as it may have so many synchronization problems. Although it may > not be a problem in millisecond range, clock drift can happen in highly > moving servers due to time change according to relativity unless they have > special clock synchronization mechanism. (e.g. Satellites) And it is not > possible to order the messages passed during a single millisecond if the > timestamp is in millisecond range as now. > > The only solution for the activity monitoring problem can be achieved by > maintaining an message counter in the data agent. The counter should be > incremented when each message is passed through the data agent and sent to > the BAM. But there also we have a problem. Since data agents exists there > in multiple threads the counter should be incremented as a atomic variable > which is an expensive mechanism. > > > *Maninda Edirisooriya* > Software Engineer > > *WSO2, Inc. *lean.enterprise.middleware. > > *Blog* : http://maninda.blogspot.com/ > *Phone* : +94 777603226 > > > On Wed, Nov 6, 2013 at 7:58 AM, Srinath Perera <[email protected]> wrote: > >> Instead, can we let users decide which timezone to be used across all BAM >> nodes? Problem is with timestamp + timezone, the time based queries get >> complicated and expensive. I think indexes will not work anymore. >> >> --Srinath >> >> >> On Tue, Nov 5, 2013 at 8:21 AM, Dunith Dhanushka <[email protected]> wrote: >> >>> Hi all, >>> >>> Currently BAM adds its current timestamp to the events that are being >>> persisted to Cassandra. But there can be situations like data publishers >>> and BAM instances are hosted in different timezones. >>> For instance APIM and BAM can be hosted in two data ceneters of two >>> different timezones. Events published from APIM will be stored in BAM with >>> BAM's current timestamp. >>> >>> So it is impossible to tell from BAM side that at what time a particular >>> event has occured in APIM. This means the time which event has been >>> published from APIM, not the time that received by BAM. >>> But if theres a way of BAM to save its timezone with events, that >>> informtion(timezone + timestamp) can be used to derive the time that events >>> had been published at APIM side. >>> >>> As a solution, in addition to timestamp we are going to store BAM's >>> system timezone alongside with events. Required changes will happen in >>> data-bridge componet. >>> >>> In fact, UTC offset of the system default timezone will be saved with >>> each event (UTC offset is the offset in milliseconds for the given time >>> zone to UTC, at the given time) so that it'd be easier for Hive queries to >>> manipulate numeric values rather than timezone name strings. >>> >>> Your feedback is highly appreciated! >>> >>> Thanks, >>> -- >>> Regards, >>> >>> Dunith Dhanushka, >>> Senior Software Engineer - BAM, >>> WSO2 Inc, >>> >>> Mobile - +94 71 8615744 >>> Blog - dunithd.wordpress.com <http://blog.dunith.com> >>> Twitter - @dunithd <http://twitter.com/dunithd> >>> >>> _______________________________________________ >>> Architecture mailing list >>> [email protected] >>> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture >>> >>> >> >> >> -- >> ============================ >> Srinath Perera, Ph.D. >> http://people.apache.org/~hemapani/ >> http://srinathsview.blogspot.com/ >> >> _______________________________________________ >> Architecture mailing list >> [email protected] >> https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture >> >> > > _______________________________________________ > Architecture mailing list > [email protected] > https://mail.wso2.org/cgi-bin/mailman/listinfo/architecture > > -- ============================ Srinath Perera, Ph.D. Director, Research, WSO2 Inc. Visiting Faculty, University of Moratuwa Member, Apache Software Foundation Research Scientist, Lanka Software Foundation Blog: http://srinathsview.blogspot.com/ Photos: http://www.flickr.com/photos/hemapani/ Phone: 0772360902
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