This is the perfect example of something that is very easy to do in Java
API but becomes overly complex in GFSH.
In the Java API, you can instantiate as many instances of the same
CacheListener class as you want, add them and then remove that specific
instance by passing it in to public void removeCacheListener(CacheListener
cl) on Region (specifically org.apache.geode.cache.AttributesMutator).
Translating that level of complexity to GFSH commands results in an
explosion of options and reference ids.
For example, if I add the same CacheListener class 3 times, then 1st one is
reference id 1, 2nd is reference id 2, etc (or zero-based if you prefer).
The amount of work required to add that in probably isn't worth it for two
reasons: 1) it's probably not that common of a use case, 2) the user could
instead write a Function or custom mbean that is deployed to the cache
server that'll keep references to the CacheListeners and handle calls to
addCacheListener and removeCacheListener for you. For that matter, you
could deploy a custom GFSH command that then triggers the addCacheListener
and removeCacheListener calls in a deployed Function. Given the ability to
do this pretty easily in a customized way is probably better than trying to
make the command overly flexible (which translates to overly complex).
I would favor improving the docs and blogging new articles that provide
details on how the user can plugin their own GFSH commands and mbeans.
On Thu, Jan 5, 2017 at 7:57 AM, Deepak Dixit <deepakdixit2...@gmail.com>
wrote:
> I would like to suggest, adding "add-cache-listener" option in addition to
> "remove-cache-listener."
> As adding listeners is as difficult as removing when doing alter region.
>
> So alter region will have following options,
>
> 1) add-cache-listener - Will add provided cache listener to existing list.
> 2) remove-cache-listener - Will remove provided cache listeners. (Here we
> may consider passing empty list will remove all listeners)
>
> And old option of cache-listeners will be removed to eliminate confusion.
>
> On Thu, Jan 5, 2017 at 5:51 PM, Zhang Xiawei <zhang_xia...@hotmail.com>
> wrote:
>
> > Not sure whether I misunderstand/miss something or not, but isn't it
> > possible that you have multiple instances of the same type of
> > CacheListener? like 2 of ListenerTypeA and 3 of ListenerTypeB, so either
> > way shown below modifies at a "category" level?
> >
> > -Xiawei
> >
> > > On 5 Jan 2017, at 1:25 AM, Anthony Baker <aba...@pivotal.io> wrote:
> > >
> > > Another consideration is that gfsh commands should be easily
> scriptable,
> > IMO.
> > >
> > > If I want to remove just one of the N listeners using this approach, I
> > would need to acquire the list of existing listeners, remove the
> deselected
> > listener, format the list, then pass it to this command. Is there a way
> to
> > do this in one simple command?
> > >
> > > Anthony
> > >
> > >> On Jan 3, 2017, at 11:08 AM, Kirk Lund <kl...@apache.org> wrote:
> > >>
> > >> +1 I'm for the approach you're proposing. As long as it's documented
> in
> > >> user docs (it's not currently) then this provides a straightforward
> use
> > of
> > >> the existing gfsh syntax without introducing too many new command
> > options.
> > >>
> > >> Create the region with two cache listeners:
> > >> $ create region --name=data
> > >> --cache-listener="my.package.ListenerTypeA,my.package.ListenerTypeB"
> > >>
> > >> Change my mind and decide to remove one of the cache listeners:
> > >> $ alter region --name=data --cache-listener="my.package.
> ListenerTypeB"
> > >>
> > >> -Kirk
> > >>
> > >>
> > >>> On Tue, Jan 3, 2017 at 10:52 AM, Kevin Duling <kdul...@pivotal.io>
> > wrote:
> > >>>
> > >>> Is this an intuitive User Experience?
> > >>>
> > >>> Given these two classes:
> > >>>
> > >>> public class ListenerTypeA extends CacheListenerAdapter implements
> > >>> Declarable
> > >>>
> > >>> and
> > >>>
> > >>> public class ListenerTypeB extends CacheListenerAdapter implements
> > >>> Declarable
> > >>>
> > >>> And they are programmatically added to a region:
> > >>>
> > >>> CacheListener listener1 = new ListenerTypeA();
> > >>>
> > >>> CacheListener listener2 = new ListenerTypeB();
> > >>>
> > >>> Region region = cache.<String,
> > >>> Customer>createClientRegionFactory(ClientRegionShortcut.CACHING_
> PROXY)
> > >>>
> > >>> .initCacheListeners(new CacheListener[]{listener1,
> > >>> listener2}).create("regionA");
> > >>>
> > >>>
> > >>> What would the expected gfsh command to remove them. Should we
> remove
> > the
> > >>> listeners via omission? For example, removing listener1 might be:
> > >>>
> > >>> alter region --name=data --cache-listener='my.package.ListenerTypeB'
> > >>>
> > >>>
> > >>> By only listing the listeners I want...either to keep and/or to add,
> > >>> listener1 which is a ListenerTypeA, would be removed.
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>
> > >>>> On Tue, Dec 20, 2016 at 2:11 PM, Kevin Duling <kdul...@pivotal.io>
> > wrote:
> > >>>>
> > >>>> I'm looking at GEODE-2236
> > >>>> <https://issues.apache.org/jira/browse/GEODE-2236> and protecting
> > >>> against
> > >>>> the NPE is trivial. But the question is, what is the right way to
> do
> > >>>> this? What is the syntax people would expect to use?
> > >>>>
> > >>>>
> > >>>> What if there are multiple listeners and you wanted to delete one or
> > more
> > >>>> of them?
> > >
> >
>
>
>
> --
> From:
>
> Deepak D Dixit
> deepakdixit2...@gmail.com
> +919028507537
>
