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From Richard Davidson <richard.davidson...@gmail.com>
Subject Re: OsgiServiceRegistry caching service references, why?
Date Thu, 11 Feb 2016 00:05:51 GMT
No I plan to only proxy the service if it is available in the camel
OsgiServiceRegistry and therefore not using blueprint. That way it can
change in the background.
Beans that are obtained in the BlueprintContainer registry will have a
blueprint proxy and will be unchanged from what they where before.

Thanks,
Richard

On Wed, Feb 10, 2016 at 11:55 PM, Quinn Stevenson <
quinn@pronoia-solutions.com> wrote:

> If I’m understanding this correctly, you’re suggesting a proxy around the
> references for ALL services - whether Blueprint has already proxied them or
> not.  Am I understanding you correctly?  If I am, it seems a bit wasteful
> to re-do what Blueprint is already doing for us.
>
> The other really strange part was when I brought the Bean Component into
> the mix.  If I didn’t inject the reference into the route building and then
> called the bean using to( “bean://..” ), I’d get the
> ServiceUnavailableException I expect.  But just injecting the reference
> breaks the behavior - even when use the Bean Component.
>
> I have some other strange examples of what works and what doesn’t if
> they’d help.  I didn’t put them in the ticket because I didn’t want to
> confuse matters.
>
>
> > On Feb 10, 2016, at 8:15 AM, Richard Davidson <
> richard.davidson.uk@gmail.com> wrote:
> >
> > Yes I agree. Creating a proxy like blueprint which wraps a service
> tracker
> > is the best option as it allows other beans in the context to keep the
> > reference to the service. Otherwise the beans would need to be totally
> > stateless and lookup the registry every time.
> >
> > On Wed, Feb 10, 2016 at 2:55 PM, Christian Schneider <
> > chris@die-schneider.net> wrote:
> >
> >> Hi Richard,
> >>
> >> I thought the issue was created by you but it was by Quinn.
> >>
> >> I think we really have to avoid caching services. Especially as this can
> >> cause problems with classloader cleanup when a bundle is uninstalled.
> >> So I think we either need to put a proxy into the service registry like
> in
> >> blueprint or we need to react on the event when the service is removed
> and
> >> clean it from the registry.
> >>
> >> Christian
> >>
> >>
> >> On 10.02.2016 15:49, Richard Davidson wrote:
> >>
> >>> Hi Christian,
> >>>
> >>> The original ticket was not logged by me, I just commented on the
> >>> behaviour. The original issue described at the start of the ticket in
> >>> which
> >>> the service object is being cached exists for scenario 2 and scenario
> 3.
> >>> Both these scenarios find the bean in the OsgiServiceRegistry, so the
> >>>  BlueprintContainerRegistry is not used.
> >>>
> >>>
> >>>
> >>> On Wed, Feb 10, 2016 at 1:47 PM, Christian Schneider <
> >>> chris@die-schneider.net> wrote:
> >>>
> >>> Hi Richard,
> >>>>
> >>>> now I understand your problem. So the problem is only with Scenario
3.
> >>>> Can you update the issue to reflect this?
> >>>>
> >>>> So does the example you mentioned in the issue (which would probably
> be
> >>>> scenario4) really not work?
> >>>> I am pretty sure it should work.
> >>>>
> >>>> Christian
> >>>>
> >>>>
> >>>> On 10.02.2016 12:51, Richard Davidson wrote:
> >>>>
> >>>> Hi.
> >>>>>
> >>>>> Sorry, I may have caused more confusion!. You are correct that if
the
> >>>>> blueprint registry is used, it will create a proxy, and the service
> can
> >>>>> come and go in the background without any issues. The issue on this
> >>>>> ticket
> >>>>> is to do with the OsgiServiceRegistry in camel. When camel tries
to
> >>>>> lookup
> >>>>> a component it goes to its registry. This is typically a composite
> >>>>> registry
> >>>>> which looks up a chain of other registries. When using camel through
> >>>>> blueprint the chain is:
> >>>>>
> >>>>> OsgiServiceRegistry -> BlueprintContainerRegistry
> >>>>>
> >>>>> The OsgiServiceRegistry does not use blueprint in any way and looks
> up
> >>>>> services in the actual OSGi registry using
> BundleContext.getService().
> >>>>> It
> >>>>> uses the 'name' as the interface to lookup. As the camel
> >>>>> OsgiServiceRegistry is first in the chain it will always be checked
> >>>>> first.
> >>>>> If it can't get the service, it will return null and the blueprint
> >>>>> registry
> >>>>> will be called. The examples below describe the behaviour:
> >>>>>
> >>>>> For each scenario I have exported an OSGI service with the interface
> >>>>> 'com.test.camel.test.Hello'.
> >>>>>
> >>>>> <b>Scenario 1</b>
> >>>>> If I use the following blueprint, the blueprint registry is used
and
> the
> >>>>> service is therefore a proxy:
> >>>>> <raw>
> >>>>> <reference id="helloBean" interface="com.test.camel.test.Hello"
/>
> >>>>>
> >>>>> <camelContext id="blueprintContext" trace="false"
> >>>>> xmlns="http://camel.apache.org/schema/blueprint">
> >>>>> <route id="timerToLog">
> >>>>> <from uri="timer:foo?period=1000" />
> >>>>> <setBody>
> >>>>> <method ref="helloBean" method="hello" />
> >>>>> </setBody>
> >>>>> <log loggingLevel="INFO" message="The message contains ${body}"
/>
> >>>>> </route>
> >>>>> </camelContext>
> >>>>> </raw>
> >>>>>
> >>>>> <b>Scenario 2</b>
> >>>>> If I use the following route the OSGi registry is used and a direct
> >>>>> reference to the bean in the OSGI registry is obtained via the
> >>>>> OSGIServiceRegistry in camel.
> >>>>> <raw>
> >>>>> <camelContext id="blueprintContext" trace="false"
> >>>>> xmlns="http://camel.apache.org/schema/blueprint">
> >>>>> <route id="timerToLog">
> >>>>> <from uri="timer:foo?period=1000" />
> >>>>> <setBody>
> >>>>> <method ref="com.test.camel.test.Hello" method="hello" />
> >>>>> </setBody>
> >>>>> <log loggingLevel="INFO" message="The message contains ${body}"
/>
> >>>>> </route>
> >>>>> </camelContext>
> >>>>> </raw>
> >>>>>
> >>>>> <b>Scenario 3</b>
> >>>>> If I lookup up a bean name that is available in both registries
then
> I
> >>>>> will
> >>>>> use the OsgiServiceRegistry, and I will not get a blueprint proxy.
> >>>>> <raw>
> >>>>>
> >>>>> <reference id="com.test.camel.test.Hello"
> >>>>> interface="com.test.camel.test.Hello" />
> >>>>>
> >>>>> <camelContext id="blueprintContext" trace="false"
> >>>>> xmlns="http://camel.apache.org/schema/blueprint">
> >>>>> <route id="timerToLog">
> >>>>> <from uri="timer:foo?period=1000" />
> >>>>> <setBody>
> >>>>> <method ref="com.test.camel.test.Hello" method="hello" />
> >>>>> </setBody>
> >>>>> <log loggingLevel="INFO" message="The message contains ${body}"
/>
> >>>>> </route>
> >>>>> </camelContext>
> >>>>>
> >>>>> </raw>
> >>>>>
> >>>>>
> >>>>>
> >>>>> The OsgiServiceRegistry currently caches the service object so if
the
> >>>>> bundle exporting com.test.camel.test.Hello restarts, then I think
the
> >>>>> route
> >>>>> will fail, but I have not tested this.
> >>>>>
> >>>>> So I think there are two potential issues:
> >>>>> 1. The OsgiServiceRegistry needs to track services.
> >>>>> 2. I think the BlueprintContainerRegistry should be first in the
> chain
> >>>>> before the OsgiServiceRegistry. This will mean if the service /
bean
> is
> >>>>> present in blueprint it will always take predence over the bean
in
> the
> >>>>> OsgiServiceRegistry.
> >>>>>
> >>>>> On Wed, Feb 10, 2016 at 8:01 AM, Christian Schneider <
> >>>>> chris@die-schneider.net> wrote:
> >>>>>
> >>>>> If you inject a blueprint reference to a service into a RouteBuilder
> >>>>> class
> >>>>>
> >>>>>> then I would expect that the camel registry is not involved
at all
> >>>>>> and you would be able to use the service proxy injected by blueprint
> >>>>>> inside the route.
> >>>>>>
> >>>>>> When the service disappears the blueprint proxy should run into
> >>>>>> ServiceUnavailableException.
> >>>>>>
> >>>>>> @Claus: Can you confirm this or am I overlooking something?
> >>>>>> This is related to this issue
> >>>>>> https://issues.apache.org/jira/browse/CAMEL-9570
> >>>>>>
> >>>>>> Christian
> >>>>>>
> >>>>>>
> >>>>>> On 09.02.2016 20:32, Quinn Stevenson wrote:
> >>>>>>
> >>>>>> In reference to the Blueprint proxy - if I use the Camel Bean
> component
> >>>>>>
> >>>>>>> to call the service (i.e. to( “bean://my-bean” ), and
I do NOT
> inject
> >>>>>>> the
> >>>>>>> service reference into the route builder, I get the dynamic
swap of
> >>>>>>> the
> >>>>>>> service implementation.  That (along with reading the Blueprint
> specs)
> >>>>>>> lead
> >>>>>>> to me to believe that the service proxy isn’t swapped
- just the
> >>>>>>> underlying
> >>>>>>> service reference.
> >>>>>>>
> >>>>>>>
> >>>>>>> --
> >>>>>>>
> >>>>>> Christian Schneider
> >>>>>> http://www.liquid-reality.de
> >>>>>>
> >>>>>> Open Source Architect
> >>>>>> http://www.talend.com
> >>>>>>
> >>>>>>
> >>>>>>
> >>>>>> --
> >>>> Christian Schneider
> >>>> http://www.liquid-reality.de
> >>>>
> >>>> Open Source Architect
> >>>> http://www.talend.com
> >>>>
> >>>>
> >>>>
> >>
> >> --
> >> Christian Schneider
> >> http://www.liquid-reality.de
> >>
> >> Open Source Architect
> >> http://www.talend.com
> >>
> >>
>
>

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