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<tobias.schoessle..mail.com> 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 <
> tobias.schoessle..mail.com> wrote:
>
>> Thanks everyone for the posts.
>>
>>..ike, 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?
>>
>>..alcolm, 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 <malcolm.edga..mail.com>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<mkienen..mail.com>
>>> 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<tobias.schoessle..mail.com> 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 <mkienen..mail.com
>>> >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<tobias.schoessle..mail.com> 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 <
>>> mkienen..mail.com
>>> >>> >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<tobias.schoessle..mail.com> 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
>>> >>> >> >
>>> >>> >>
>>> >>> >
>>> >>>
>>> >>
>>> >
>>>
>>
>>
>
This archive was generated by hypermail 2.0.0 : Thu Jul 30 2009 - 17:34:14 EDT