On Feb 26, 2011, at 9:36 AM, Sergiu Dumitriu wrote: > On 02/26/2011 08:58 AM, Vincent Massol wrote: >> Hi Sergiu, >> >> On Feb 26, 2011, at 12:00 AM, sdumitriu (SVN) wrote: >> >>> Author: sdumitriu >>> Date: 2011-02-26 00:00:44 +0100 (Sat, 26 Feb 2011) >>> New Revision: 34960 >>> >>> Added: >>> platform/core/trunk/xwiki-eventstream/ >>> platform/core/trunk/xwiki-eventstream/pom.xml >>> platform/core/trunk/xwiki-eventstream/src/ >>> platform/core/trunk/xwiki-eventstream/src/main/ >>> platform/core/trunk/xwiki-eventstream/src/main/java/ >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/ >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/ >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/ >>> >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/Event.java >>> >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/EventFactory.java >>> >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/EventGroup.java >>> >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/EventStream.java >>> >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/internal/ >>> >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/internal/DefaultEvent.java >>> >>> platform/core/trunk/xwiki-eventstream/src/main/java/org/xwiki/eventstream/internal/DefaultEventFactory.java >>> platform/core/trunk/xwiki-eventstream/src/main/resources/ >>> platform/core/trunk/xwiki-eventstream/src/main/resources/META-INF/ >>> >>> platform/core/trunk/xwiki-eventstream/src/main/resources/META-INF/components.txt >>> platform/core/trunk/xwiki-eventstream/src/test/ >>> platform/core/trunk/xwiki-eventstream/src/test/java/ >>> platform/core/trunk/xwiki-eventstream/src/test/java/org/ >>> platform/core/trunk/xwiki-eventstream/src/test/java/org/xwiki/ >>> platform/core/trunk/xwiki-eventstream/src/test/java/org/xwiki/eventstream/ >>> >>> platform/core/trunk/xwiki-eventstream/src/test/java/org/xwiki/eventstream/EventAndFactoryTest.java >>> >>> platform/core/trunk/xwiki-eventstream/src/test/java/org/xwiki/eventstream/EventGroupTest.java >>> Modified: >>> platform/core/trunk/pom.xml >>> Log: >>> XWIKI-6047: New EventStream component >> >> That was new to me. Was this discussed (it's possible I missed a mail on the >> list)? > > I needed a way to store user messages without depending on the activity > stream plugin. This is just a wrapper on top of the activity stream plugin. > > Now that you mentioned it, I'm not sure the "Event" term is 100% > compatible with "user message", WDYT? > >>> From the jira it seems this module is meant to be a replacement of the >>> ActivityStream plugin, right? If so what's the strategy to replace it >>> (timing, backward compat, etc)? > > At some point yes, but we need the storage module before that. Any ETA > for storage? > >> There seems to be a notion of Event similar to that of the Observation >> module. >> Maybe Event is not the right term here seems the javadoc says "A recorded >> event that happened at some point in the wiki". Maybe something like >> ArchiveEvent, PastEvent, SavedEvent, etc And maybe these events should >> extend the Observation Event and add new fields (date, etc)? Or maybe it's >> better to not extend but have a field that is the original Observation Event >> object? Or maybe not and it's better to have no relationship to the >> Observation module to be independent? In any case this should probably be >> discussed/explained. > > Events can come from other sources than observation events, so it's not > equivalent. Most activity events will be created at the same time as an > observation event is fired. > > Personally I don't like to relate them. They are both effects of some > activity in the wiki, but one can occur without the other and vice-versa. > - not all observation events are logged (none of the rendering events > are that interesting, storing them will just be a waste of database > storage; same with ActionExecutionEvents, that would be duplicating > analytics and statistics) > - not all activity events will be created through notifications.
hmm I'm not sure about this. I view it the other way around, ie all events must go through notifications and some get saved (not all of course). Although this puts more limitation it seems a stronger and simpler architecture to me: * all events are sent as observation events * this allows features such as remote events almost transparently * this allows saving events transparently too * allows adding lots of other feature in the future (logging of events for debug purpose/real time view of what's happening in the system, etc) IMO adding a xwiki-observation-history or -storage module makes the architecture more cohesive and makes the observation module as a whole more important. Having decoupling is good in general but has its limitations: * necessity to write bridges between systems (serialization, marshalling) * more ways for users to use them and thus needs more written best practices to give directions * makes it harder for a newcomer to use them Right now I'm more inclined to say that the new "eventstream" should be implemented as xwiki-observation-store/storage/history. But we need more input from other committers too. And this can be refactored later on if we flag the new module as experimental and unstable in the release notes for 3.0 to ensure people won't use it (that won't ensure anything but will cover ourselves a bit... hey didn't you read the release notes? ;)). We'd need to refactor it in 3.1 though if we want to go in that direction. > I see the relationship ObservationEvent->ActivityStreamEvent as a mere > technological evolution accident, and not something done on complete > purpose. Initially this was a way to decouple the ActivityStream plugin > from the core, since events were already being sent (the old > notification events), and there was no good reason to hardcore AS in the > core. Then Notifications were replaced by ObservationEvents, then more > events and more activities were added to support the new and improved > Activity widget, and now I'm introducing clean activity events to be > used for a wider range of events. What is a "wider range of events"? What kind of events wouldn't be handled by the Observation module? > The real relationship between the two > types of events should actually be the other way around. Something > happens in the wiki, so we: > 1/ store this for historical reasons (view the activity in the > dashboard, security audits, statistics, etc.) > 2/ let possible interested parties know about this, so they can clear > their caches, or compute some data, or send mails, or whatever it is > they want to do when something relevant happens. It's really the other way around. Events must be sent first and then listeners do what they want: store them, etc. This is the only performant and architecture-sound way I know to handle this. Otherwise it means you're considering storage a special action, which it doesn't have to be. It's an action like any other action that can happen on events. > And since geeks start counting at 0 and we have such a cool platform: > 0/ check that the activity is valid by sending a cancelable observation > event, and if someone doesn't like this, abort the whole process and > throw an error right in the user's face. > >> Maybe the Obervation module should be split in one more submodule called >> xwiki-observation-store or xwiki-observation-history? It seems to me this >> could be about historizing the events sent by the Observation managed. >> >> To be honest, I haven't really thought about it enough (would need to load >> the code in my IDE). >> >> I find that this commit happens quite late in the release cycle (3 days >> before end of milestone) and would have warranted some earlier discussion. > > It happens when it's ready, I couldn't have committed it before it was > done. There were discussions when the activity stream plugin was > designed, Marius did a good job from the start; I found it good enough > to use in the future, so I simply pruned the nasty part > (param1..param5), I updated some methods to current practices (replaced > strings with proper References), and I ironed out some method names. > Sprinkled a bit of Javadoc on top, and it's out without another couple > of weeks of discussions. It can be enhanced on the run, no need to halt > everything until it's perfect, because it never will be. Sure about not being perfect (this is not the issue), and I've not asked to stop anything. Thanks -Vincent > >> It's ok, I'm not asking to rollback, just saying that something this >> important from an architecture point of view should rather be done earlier >> and discussed. > > -- > Sergiu Dumitriu _______________________________________________ devs mailing list [email protected] http://lists.xwiki.org/mailman/listinfo/devs
