Hi Tobias, I've not used the cache synchronization before, but I was under the impression that the main overhead is when inserts/updates/deletes are done, not when selects are done. When you do an insert/update/delete, that information must be broadcast, but selects do not. I'm sure someone will correct me if I am wrong on this. :-)
mrg On Thu, Jul 30, 2009 at 5:23 PM, Tobias Schoessler<[email protected]> wrote: > So thank you for all the suggestions. The solution we finally ended up with > was the one Mike actually suggested intitially. We got our multicast ip, > dropped the latest Jgroups.jar into both webapps lib directories, selected > Jgroups as the Syncronisation mechanism in the cayenne modeller, used the > default jgroups udp.xml config file patched with our multicast ip address > and 'snapp' the contexts were synchronized. Very satisfying - Cayenne > rocks.! :) > > Before this I went down the route of trying to make cayenne use the global > JVM scope to store the shared cache. I moved the cayenne.jar up on the > tomcat shared lib directory, out of the two web app lib folders. This did > not work out well, I got stuck at the point where one web app worked fine > the other one threw class cast exception on the mapping objects saying it > cannot cast the types on itself. I assume this is due to the fact that both > webapps had their own copies of the mapping classes. I tried moving them up > into the shared tomcat lib aswell, but then they could not see the web app > specific classes anymore. So anyway I am happy with our Jgroups solution > now. > > The documentation reads lthis setup has some overhead. Does anybody have > experience/numbers how much performance you loose when using jgroups > syncronised caches compared to local cache? > > thanks again everyone. > > On Thu, Jul 30, 2009 at 10:47 AM, Tobias Schoessler < > [email protected]> wrote: > >> Thanks everyone for the posts. >> >> @Mike, I am still not convinced that using the Remote Notification Feature >> is really nessecary here. After all, there seems to be a JVM shared between >> webapps in Tomcat and the article posted seems to proof that there is a >> possiblity to share information between the webapps on a JVM level. So I >> think that using Remote Notification, which I understand to be designed for >> Cross JVM notification creates too much overhead. >> >> You mentioned the possibility of sharing the DataContext between the >> webapps. I think I have to explore this possibility first, as this would >> have less overhead compared to the notification based solution. >> Currently I am using the >> org.objectstyle.cayenne.conf.ServletUtil.getSessionContext(request.getSession()) >> to obtain my DataContexts per request. >> If I could change the scope the DataContexts are stored to cross web app >> scope instead of session scope I could share the DataContexts between the >> two web apps. Assuming that I can setup the two webapps to share the same >> session Ids as described in the article. >> >> This might be a no go for me as the two contexts use different >> authentication realms - I have to check this. But even then wouldn't it be >> possbile to configure the cayenne shared cache to use this cross web context >> scope for its shared cache. Then I could use >> org.objectstyle.cayenne.conf.ServletUtil.getSessionContext(session) in the >> two web apps transparently and cayenne would refresh the DataContext from >> this shared cache in the background. Could somebody point me to where this >> shared cayenne cache is configured to have its scope? I assume it uses JVM >> static scope? >> >> @Malcolm, thanks for suggesting this alternative. If I understand you >> correctly you suggest to switch off the cayenne cache alltogether and use >> the jsptag based caching of the OScache project? The problem with this is >> that not all my responses are generated from jsptags. I have many ajax >> requests generating json responses without bothering the jsp container. >> >> Tobias >> >> >> On Thu, Jul 30, 2009 at 3:00 AM, Malcolm Edgar >> <[email protected]>wrote: >> >>> You can also use OSCache with Cayenne and have the cached queries >>> expire frequently, i.e. after 30 seconds >>> >>> regards Malcolm Edgar >>> >>> On Thu, Jul 30, 2009 at 6:36 AM, Mike Kienenberger<[email protected]> >>> wrote: >>> > Before you make your own custom solution, you might want to read up on >>> > Javagroup. It might not be a problem to use it in your environment. >>> > >>> > The main page starts off with this: >>> > >>> > http://www.jgroups.org/ >>> > ================================== >>> > JGroups is a toolkit for reliable multicast communication. >>> > (Note that this doesn't necessarily mean IP Multicast, JGroups can >>> > also use transports such as TCP). >>> > >>> > [...] >>> > >>> > JGroups comes with a number of protocols (but anyone can write their >>> > own), for example >>> > * Transport protocols: UDP (IP Multicast), TCP, JMS >>> > >>> > ================================== >>> > >>> > So even if the TCP version doesn't do what you need, you might find it >>> > easier to write your own Jgroup protocol than to write your own >>> > cayenne event bridge. It's more likely to be documented and there >>> > will be more examples/end users to ask questions of. There might even >>> > be a tomcat shared session protocol out there somewhere. >>> > >>> > >>> > On Wed, Jul 29, 2009 at 4:16 PM, Tobias >>> > Schoessler<[email protected]> wrote: >>> >> well i am reading this from the documentation: >>> >> >>> >> "... At the minimum, JMS setup requires a JMS server running, and >>> subjects >>> >> for each of the DataDomains to be configured. JavaGroups is >>> peer-to-peer >>> >> library that is embedded into applications. Default configuration >>> provided >>> >> by CayenneModeler will work out of the box, provided that IP multicast >>> is >>> >> enabled on the network." >>> >> >>> >> for the JMS solution the JMS server setup is a problem >>> >> for the JavaGroups setup the "IP multicast is enabled on the network." >>> is a >>> >> problem >>> >> >>> >> so for the custom tranport mechanism that you mentioned I stumbled >>> upon >>> >> this here >>> >> >>> >> >>> http://jee-bpel-soa.blogspot.com/2009/06/session-sharing-in-apache-tomcat.html >>> >> >>> >> which seems to describe cross context data sharing on tomcat web >>> contexts >>> >> >>> >> but is there any code to look at to see how a custom transport >>> mechanism can >>> >> be setup? >>> >> >>> >> Tobias >>> >> >>> >> >>> >> On Wed, Jul 29, 2009 at 8:28 PM, Mike Kienenberger <[email protected] >>> >wrote: >>> >> >>> >>> I've never set it up, but it's easily configurable. >>> >>> >>> >>> If you don't like the javagroups or JMS methodologies, you can define >>> >>> your own -- I don't know what tomcat app-data-sharing ability is >>> >>> available -- it probably depends on the container, but I don't >>> >>> remember reading about any in the past. >>> >>> >>> >>> However, the docs seem to indicate that using Javagroups is pretty >>> >>> painless with no external configuration to deal with. >>> >>> >>> >>> I have a Cayenne 1.1.x application I wrote that used remote >>> >>> notification internally to broadcast events between sessions, so I >>> >>> know it's not difficult to set up and define your own event >>> >>> broadcaster. My guess is that doing it for javagroups is pretty easy >>> >>> since it sounds like a matter of just filling in the forms on the >>> >>> modeler. >>> >>> >>> >>> On Wed, Jul 29, 2009 at 2:15 PM, Tobias >>> >>> Schoessler<[email protected]> wrote: >>> >>> > Thanks Mike, >>> >>> > >>> >>> > so the answer is yes, this can only be done using remote >>> notification? is >>> >>> > this correct? >>> >>> > >>> >>> > Isn't there a way to share the cache among two web application >>> scopes >>> >>> > without going through the hassle of setting up remote notification? >>> >>> > >>> >>> > When the two webapps are running on the same physical machine, >>> inside the >>> >>> > same application server this seems overkill. >>> >>> > >>> >>> > Tobias >>> >>> > >>> >>> > On Wed, Jul 29, 2009 at 6:50 PM, Mike Kienenberger < >>> [email protected] >>> >>> >wrote: >>> >>> > >>> >>> >> Yes, >>> >>> >> >>> >>> >> Here's a Cayenne 2.0 document on it: >>> >>> >> >>> >>> >> http://cayenne.apache.org/doc20/configuring-caching-behavior.html >>> >>> >> >>> >>> >> For 3.0: >>> >>> >> >>> >>> >> http://cayenne.apache.org/doc/configuring-caching-behavior.html >>> >>> >> >>> >>> >> On Wed, Jul 29, 2009 at 12:46 PM, Tobias >>> >>> >> Schoessler<[email protected]> wrote: >>> >>> >> > Hi, >>> >>> >> > >>> >>> >> > is it possible to sync the cayenne cache of two web applications >>> >>> running >>> >>> >> in >>> >>> >> > the same tomcat? >>> >>> >> > >>> >>> >> > I observe one web app showing outdated data when the other is >>> >>> committing >>> >>> >> > updates. Both apps are using the same mapping configuration. >>> >>> >> > >>> >>> >> > Do I need to use remote notification for this? >>> >>> >> > >>> >>> >> > thanks >>> >>> >> > >>> >>> >> > Tobias >>> >>> >> > >>> >>> >> >>> >>> > >>> >>> >>> >> >>> > >>> >> >> >
