Re: [osgi-dev] Double config
Hi Neil, Thanks for the tips. > With regard to "testing bouncing", there are two sides to this question: the > component being bounced, and the other components that may be exposed to it > bouncing. > > The component itself should never actually know that it is being, or has > been, bounced. SCR always creates a new instance for each activation… Yeah, that was one of my learnings during this iteration. The simplicity of using a static component cannot be understated. By removing as much threading and dynamic components as possible, it makes the system **MUCH** more easy to reason, and at least in my case with no perceptible performance loss. > The harder question is about components that deliberately expose themselves > to the bouncing of other components – in other words, they have dynamic > service references – and/or expose themselves to dynamic configuration > changes by having a modified method. Tim talked about components that require > heavyweight initialisation... to implement such a component you might write a > modify method to accept dynamic config changes and then internally implement > some kind of damping mechanism. This gets you into some slightly hairy > multithreading code. Yeah… I’m trying to avoid that when possible. > I don't have a good answer myself yet for testing this kind of code, it seems > like even the best available practices are still quite primitive and > probabilistic, e.g. running the same code thousands of times and hoping to > find an error. I would love to find something better. I get the impression that the only thing to do is reason about the code. I am finding that there are two places where there is potential for things to go wrong: (1) concurrency due to “regular” multithreading and (2) when using promises. Concurrency is a little easier to reason, at least for me. I have tried to limit exposure to these risks as much as possible. I think I have this pretty much under control, but since I am relying on my ability to reason and don’t have a conclusive means of testing, I have no guarantee that I have not reasoned incorrectly. As for promises, the bigger challenge is protecting against services that come and go. I am finding that dealing with these dynamics is more challenging than concurrency. However, by reducing multithreading (accepting synchronous processing as much as possible instead of worrying too much in advance about performance), I have greatly reduced these risks and, at least for now, the timing problems I was having. Although I understand that it is not good practice to linger too long in, for example, an activate method, by moving back “long” processes (in the order of a second or so) synchronously into the same thread, I have greatly simplified my system, at the expense of a startup time that is about 5-10 seconds slower. I can certainly live with that. KISS Thanks again. =David ___ OSGi Developer Mail List osgi-dev@mail.osgi.org https://mail.osgi.org/mailman/listinfo/osgi-dev
Re: [osgi-dev] Double config
>> Unless maybe there is a bug in SCR for some edge case (felix version 2.0.2). > > This is indeed my suspicion based on what you have described. Have you tried > using a later SCR implementation, just in case it's a bug that's already been > fixed? Thanks, Neil! I updated to 2.0.14, and the problem has gone away. As an extra bonus, there is no more bouncing, either. I could never figure out why the system was bouncing, so I guess this explains it. :-) Cheers, =David ___ OSGi Developer Mail List osgi-dev@mail.osgi.org https://mail.osgi.org/mailman/listinfo/osgi-dev
Re: [osgi-dev] Double config
On Sun, Aug 26, 2018 at 1:35 AM David Leangen via osgi-dev <
osgi-dev@mail.osgi.org> wrote:
>
> Hi,
>
> Thank you again for all the great tips in this thread. I have taken the
> time to review concurrency, reread all the blogs, articles, and email
> messages in detail, and I have done a fairly thorough review of all my
> code. I have identified a lot of places where there was potential for
> concurrency errors, and I made a lot of simplifications (mostly by
> eliminating any clever use of concurrency or synchronization when it wasn’t
> really providing any tangible benefit, and only introducing risk). I also
> reviewed again the DS lifecycle, as well as Trackers. I am pretty confident
> that my understanding of the concurrent issues, and consequently my system,
> are now in good shape. I think I can handle the dynamics now in a robust
> way (though I still don’t know how to test for it to confirm).
>
> However, I am experiencing one problem on startup still that baffles me.
>
> Take this component:
>
>
> @Component(
> factory = ...,
> configurationPid = ...,
> configurationPolicy = ConfigurationPolicy.REQUIRE)
> public class D
> implements Descriptor
> {
> @Reference( scope = ReferenceScope.PROTOTYPE_REQUIRED )
> private WriterFactory.JsonWriterFactory factory;
>
> @Activate
> void activate( Configuration.Config config )
> {
> ...
> }
>
> ...
> }
>
>
> There is really nothing more to the component that this. One static
> reference (which is satisfied), and a required config (which is available).
>
> The factory basically looks like this (called from a different component
> that instantiates this tracker):
>
>
> public class ComponentFactoryTracker
> extends ServiceTracker
> {
> public ConfinementAwareComponentFactoryTracker( BundleContext context,
> Filter filter )
> {
> super( context, filter, null );
> }
>
> @Override
> public ComponentInstance addingService(
> ServiceReference reference )
> {
> final ComponentFactory cf = context.getService( reference );
> final Dictionary properties = new Hashtable<>();
> properties.put( ... );
> final ComponentInstance instance = cf.newInstance( properties );
> return instance;
> }
>
> @Override
> public void removedService( ServiceReference
> reference, ComponentInstance instance )
> {
> context.ungetService( reference );
> instance.dispose();
> }
> }
>
> Fairly simple.
>
> The system starts up, and the D component (and others like it) also
> starts. Then bouncing happens. When things finally settle down after one
> bounce, D (and others like it) gets deactivated. This is where I start
> pulling my hair out. **Why** does it get deactivated???
>
I can't explain this either. The only suggestions I can make are:
1) Write a deactivate method, stick a breakpoint on it and look at the
stack. That might give you a clue as to why and how you got there.
2) Create a demonstrator project and raise a bug against the SCR
implementation.
>
> —> The one and only static reference is available. Check.
>
> —> The configuration is available. Check.
>
> —> The ComponentFactory services are enabled. Check.
>
> However, despite all the prerequisites being available, D (and others) are
> getting deactivated. I even created an immediate service that references D
> (and others) to ensure that somebody was calling it. Nothing. Nada. All
> that I can validate is that as D (and others) get deactivated, they are
> unbound from this test service.
>
> If I restart any bundle that causes D to refresh, then the state of the
> system comes up correctly. It is only upon initial startup that this
> problem occurs.
>
> If I try injecting some service that potentially changes startup order,
> sometimes it works, but I have not yet figured out the pattern. In any
> case, since the prerequisites for the service are available, I don’t see
> why on Earth that should matter, anyway. Unless maybe there is a bug in SCR
> for some edge case (felix version 2.0.2).
>
This is indeed my suspicion based on what you have described. Have you
tried using a later SCR implementation, just in case it's a bug that's
already been fixed?
Neil
>
>
> I am at a loss...
>
>
> Cheers,
> =David
>
>
>
> On Jul 14, 2018, at 4:05, David Leangen via osgi-dev <
> osgi-dev@mail.osgi.org> wrote:
>
>
> Hi Tim,
>
> What is a good way to test for robustness against this phenomenon?
>
>
> Again, I wish to go on record as saying that bouncing does not mean that
> anything is wrong, nor is it intrinsically bad.
>
>
> Thanks. Understood. I did not mean to imply anything about “goodness” or
> “badness”, but it is good to have that on record.
>
> So, my question was: knowing that this happens, is there a good way to
> test against it? My understanding is that currently there is not.
>
>
> Cheers,
> =David
>
> ___
> OSGi
Re: [osgi-dev] Double config
With regard to "testing bouncing", there are two sides to this question: the component being bounced, and the other components that may be exposed to it bouncing. The component itself should never actually know that it is being, or has been, bounced. SCR always creates a new instance for each activation, so unless you are storing state in static fields (hopefully you don't need me to tell you that would be a bad idea!) your component only needs to deal with a straightforward start/stop lifecycle. For example when it starts, it may as well be the only time it has ever started. If you have specified optional configuration or any optional service references then you need to deal with the possibility that config/services may be null, and you should write unit tests for all combinations of config/services being unbound and unbound. Obviously you don't want too many optional references because the number of required test cases rises exponentially. The harder question is about components that deliberately expose themselves to the bouncing of other components – in other words, they have dynamic service references – and/or expose themselves to dynamic configuration changes by having a modified method. Tim talked about components that require heavyweight initialisation... to implement such a component you might write a modify method to accept dynamic config changes and then internally implement some kind of damping mechanism. This gets you into some slightly hairy multithreading code. I don't have a good answer myself yet for testing this kind of code, it seems like even the best available practices are still quite primitive and probabilistic, e.g. running the same code thousands of times and hoping to find an error. I would love to find something better. Hope this helps, Neil On Fri, Jul 13, 2018 at 8:05 PM David Leangen via osgi-dev < osgi-dev@mail.osgi.org> wrote: > > Hi Tim, > > >> What is a good way to test for robustness against this phenomenon? > > > > Again, I wish to go on record as saying that bouncing does not mean that > anything is wrong, nor is it intrinsically bad. > > Thanks. Understood. I did not mean to imply anything about “goodness” or > “badness”, but it is good to have that on record. > > So, my question was: knowing that this happens, is there a good way to > test against it? My understanding is that currently there is not. > > > Cheers, > =David > > ___ > OSGi Developer Mail List > osgi-dev@mail.osgi.org > https://mail.osgi.org/mailman/listinfo/osgi-dev ___ OSGi Developer Mail List osgi-dev@mail.osgi.org https://mail.osgi.org/mailman/listinfo/osgi-dev
Re: [osgi-dev] Double config
David,
In my own journey I have had (and still does have) my share of moments
where I'm not sure what's happening. We are still on Equinox/PDE (can't
wait to switch to BND but that will have to wait a bit), and there I have
used the tracing to get insight into the service registry events. With
Equinox you can turn tracing under o.e.osgi. The keys are debug and
debug/services. This activates the tracing from Felix SCR, so that is not
limited to Equinox, but I'm not sure how you would activate it if not using
Equinox.
HTH,
Alain
On Sat, Aug 25, 2018 at 8:35 PM David Leangen via osgi-dev <
osgi-dev@mail.osgi.org> wrote:
>
> Hi,
>
> Thank you again for all the great tips in this thread. I have taken the
> time to review concurrency, reread all the blogs, articles, and email
> messages in detail, and I have done a fairly thorough review of all my
> code. I have identified a lot of places where there was potential for
> concurrency errors, and I made a lot of simplifications (mostly by
> eliminating any clever use of concurrency or synchronization when it wasn’t
> really providing any tangible benefit, and only introducing risk). I also
> reviewed again the DS lifecycle, as well as Trackers. I am pretty confident
> that my understanding of the concurrent issues, and consequently my system,
> are now in good shape. I think I can handle the dynamics now in a robust
> way (though I still don’t know how to test for it to confirm).
>
> However, I am experiencing one problem on startup still that baffles me.
>
> Take this component:
>
>
> @Component(
> factory = ...,
> configurationPid = ...,
> configurationPolicy = ConfigurationPolicy.REQUIRE)
> public class D
> implements Descriptor
> {
> @Reference( scope = ReferenceScope.PROTOTYPE_REQUIRED )
> private WriterFactory.JsonWriterFactory factory;
>
> @Activate
> void activate( Configuration.Config config )
> {
> ...
> }
>
> ...
> }
>
>
> There is really nothing more to the component that this. One static
> reference (which is satisfied), and a required config (which is available).
>
> The factory basically looks like this (called from a different component
> that instantiates this tracker):
>
>
> public class ComponentFactoryTracker
> extends ServiceTracker
> {
> public ConfinementAwareComponentFactoryTracker( BundleContext context,
> Filter filter )
> {
> super( context, filter, null );
> }
>
> @Override
> public ComponentInstance addingService(
> ServiceReference reference )
> {
> final ComponentFactory cf = context.getService( reference );
> final Dictionary properties = new Hashtable<>();
> properties.put( ... );
> final ComponentInstance instance = cf.newInstance( properties );
> return instance;
> }
>
> @Override
> public void removedService( ServiceReference
> reference, ComponentInstance instance )
> {
> context.ungetService( reference );
> instance.dispose();
> }
> }
>
> Fairly simple.
>
> The system starts up, and the D component (and others like it) also
> starts. Then bouncing happens. When things finally settle down after one
> bounce, D (and others like it) gets deactivated. This is where I start
> pulling my hair out. **Why** does it get deactivated???
>
> —> The one and only static reference is available. Check.
>
> —> The configuration is available. Check.
>
> —> The ComponentFactory services are enabled. Check.
>
> However, despite all the prerequisites being available, D (and others) are
> getting deactivated. I even created an immediate service that references D
> (and others) to ensure that somebody was calling it. Nothing. Nada. All
> that I can validate is that as D (and others) get deactivated, they are
> unbound from this test service.
>
> If I restart any bundle that causes D to refresh, then the state of the
> system comes up correctly. It is only upon initial startup that this
> problem occurs.
>
> If I try injecting some service that potentially changes startup order,
> sometimes it works, but I have not yet figured out the pattern. In any
> case, since the prerequisites for the service are available, I don’t see
> why on Earth that should matter, anyway. Unless maybe there is a bug in SCR
> for some edge case (felix version 2.0.2).
>
>
> I am at a loss...
>
>
> Cheers,
> =David
>
>
>
> On Jul 14, 2018, at 4:05, David Leangen via osgi-dev <
> osgi-dev@mail.osgi.org> wrote:
>
>
> Hi Tim,
>
> What is a good way to test for robustness against this phenomenon?
>
>
> Again, I wish to go on record as saying that bouncing does not mean that
> anything is wrong, nor is it intrinsically bad.
>
>
> Thanks. Understood. I did not mean to imply anything about “goodness” or
> “badness”, but it is good to have that on record.
>
> So, my question was: knowing that this happens, is there a good way to
> test against it? My understanding is that currently there is not.
>
>
> Che
Re: [osgi-dev] Double config
Hi,
Thank you again for all the great tips in this thread. I have taken the time to
review concurrency, reread all the blogs, articles, and email messages in
detail, and I have done a fairly thorough review of all my code. I have
identified a lot of places where there was potential for concurrency errors,
and I made a lot of simplifications (mostly by eliminating any clever use of
concurrency or synchronization when it wasn’t really providing any tangible
benefit, and only introducing risk). I also reviewed again the DS lifecycle, as
well as Trackers. I am pretty confident that my understanding of the concurrent
issues, and consequently my system, are now in good shape. I think I can handle
the dynamics now in a robust way (though I still don’t know how to test for it
to confirm).
However, I am experiencing one problem on startup still that baffles me.
Take this component:
@Component(
factory = ...,
configurationPid = ...,
configurationPolicy = ConfigurationPolicy.REQUIRE)
public class D
implements Descriptor
{
@Reference( scope = ReferenceScope.PROTOTYPE_REQUIRED )
private WriterFactory.JsonWriterFactory factory;
@Activate
void activate( Configuration.Config config )
{
...
}
...
}
There is really nothing more to the component that this. One static reference
(which is satisfied), and a required config (which is available).
The factory basically looks like this (called from a different component that
instantiates this tracker):
public class ComponentFactoryTracker
extends ServiceTracker
{
public ConfinementAwareComponentFactoryTracker( BundleContext context,
Filter filter )
{
super( context, filter, null );
}
@Override
public ComponentInstance addingService( ServiceReference
reference )
{
final ComponentFactory cf = context.getService( reference );
final Dictionary properties = new Hashtable<>();
properties.put( ... );
final ComponentInstance instance = cf.newInstance( properties );
return instance;
}
@Override
public void removedService( ServiceReference reference,
ComponentInstance instance )
{
context.ungetService( reference );
instance.dispose();
}
}
Fairly simple.
The system starts up, and the D component (and others like it) also starts.
Then bouncing happens. When things finally settle down after one bounce, D (and
others like it) gets deactivated. This is where I start pulling my hair out.
**Why** does it get deactivated???
—> The one and only static reference is available. Check.
—> The configuration is available. Check.
—> The ComponentFactory services are enabled. Check.
However, despite all the prerequisites being available, D (and others) are
getting deactivated. I even created an immediate service that references D (and
others) to ensure that somebody was calling it. Nothing. Nada. All that I can
validate is that as D (and others) get deactivated, they are unbound from this
test service.
If I restart any bundle that causes D to refresh, then the state of the system
comes up correctly. It is only upon initial startup that this problem occurs.
If I try injecting some service that potentially changes startup order,
sometimes it works, but I have not yet figured out the pattern. In any case,
since the prerequisites for the service are available, I don’t see why on Earth
that should matter, anyway. Unless maybe there is a bug in SCR for some edge
case (felix version 2.0.2).
I am at a loss...
Cheers,
=David
> On Jul 14, 2018, at 4:05, David Leangen via osgi-dev
> wrote:
>
>
> Hi Tim,
>
>>> What is a good way to test for robustness against this phenomenon?
>>
>> Again, I wish to go on record as saying that bouncing does not mean that
>> anything is wrong, nor is it intrinsically bad.
>
> Thanks. Understood. I did not mean to imply anything about “goodness” or
> “badness”, but it is good to have that on record.
>
> So, my question was: knowing that this happens, is there a good way to test
> against it? My understanding is that currently there is not.
>
>
> Cheers,
> =David
>
> ___
> OSGi Developer Mail List
> osgi-dev@mail.osgi.org
> https://mail.osgi.org/mailman/listinfo/osgi-dev
___
OSGi Developer Mail List
osgi-dev@mail.osgi.org
https://mail.osgi.org/mailman/listinfo/osgi-dev
Re: [osgi-dev] Double config
Hi Tim, >> What is a good way to test for robustness against this phenomenon? > > Again, I wish to go on record as saying that bouncing does not mean that > anything is wrong, nor is it intrinsically bad. Thanks. Understood. I did not mean to imply anything about “goodness” or “badness”, but it is good to have that on record. So, my question was: knowing that this happens, is there a good way to test against it? My understanding is that currently there is not. Cheers, =David ___ OSGi Developer Mail List osgi-dev@mail.osgi.org https://mail.osgi.org/mailman/listinfo/osgi-dev
Re: [osgi-dev] Double config
h.com <http://www.bosch.com/> >>>> Tel. +49 7153 666-1155 | dirk.fa...@de.bosch.com >>>> <mailto:dirk.fa...@de.bosch.com> >>>> >>>> Sitz: Stuttgart, Registergericht: Amtsgericht Stuttgart, HRB 14000; >>>> Aufsichtsratsvorsitzender: Franz Fehrenbach; Geschäftsführung: Dr. Volkmar >>>> Denner, >>>> Prof. Dr. Stefan Asenkerschbaumer, Dr. Michael Bolle, Dr. Rolf Bulander, >>>> Dr. Stefan Hartung, Dr. Markus Heyn, >>>> Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Peter Tyroller >>>> >>>> >>>> Von: osgi-dev-boun...@mail.osgi.org >>>> <mailto:osgi-dev-boun...@mail.osgi.org> >>>> [mailto:osgi-dev-boun...@mail.osgi.org >>>> <mailto:osgi-dev-boun...@mail.osgi.org>] Im Auftrag von Tim Ward via >>>> osgi-dev >>>> Gesendet: Donnerstag, 12. Juli 2018 10:22 >>>> An: Peter Kriens mailto:peter.kri...@aqute.biz>>; >>>> OSGi Developer Mail List >>> <mailto:osgi-dev@mail.osgi.org>> >>>> Betreff: Re: [osgi-dev] Double config >>>> >>>> Hi David, >>>> >>>> >>>> This is a gift! :-) It means your code is not handling the dynamics >>>> correctly and now you know it! >>>> >>>> I’m not sure that there’s quite enough evidence to come to this >>>> conclusion. It could simply be that everything is working fine with a >>>> static policy, and working the way that DS is supposed to. In general a DS >>>> component being bounced like this is nothing to worry about, it’s just a >>>> change rippling through the system, and it’s typically resolved in very >>>> short order. If you do want to reason about why, however, then there are >>>> several places to look. >>>> >>>> For some reason, the Component gets activated, deactivated, then activated >>>> again, which is not desirable. >>>> ... >>>> 1. How can I figure out why this is happening. I have tried many >>>> approaches, but can’t seem to get a clue as to why this is happening. >>>> Since it generally doesn’t seem to happen for other configured components, >>>> I am assuming that it is not a Configurator problem. >>>> >>>> From the rest of your email it is clear that the configured component >>>> provides a service. This will make it lazy by default. You have also >>>> stated that you’re using has a required configuration policy. Therefore it >>>> will only be activated when: >>>> >>>> There is a configuration present >>>> All of the mandatory services are satisfied >>>> Someone is actually using the service >>>> >>>> The component will then be deactivated when any of these things are >>>> no-longer true, and so this means that your component may be being bounced >>>> for several reasons, only one of which is to do with configuration. >>>> >>>> While it seems unlikely to me, you seem to be fairly convinced that the >>>> configuration is at fault so lets start there. >>>> >>>> Does the generated XML file in your bundle actually say that the >>>> configuration is required. This is the configuration used by DS (not the >>>> annotations) at runtime. It’s unlikely that this has gone wrong, but it’s >>>> an easy check >>>> Do you have more than one way of putting configuration into the runtime? >>>> If you are also using File Install, or some other configuration management >>>> agent, then it’s entirely possible that you’re seeing a configuration >>>> update occurring. >>>> Do you have multiple configuration bundles which both contain a >>>> configuration for this component? The configurator will process these one >>>> at a time, and it will result in configuration bouncing >>>> Is it possible that something is forcing a re-resolve of your >>>> configuration bundle or the configurator? This could easily trigger the >>>> configurations to be reprocessed. >>>> >>>> Now in my view the most likely reason for this behaviour is that the >>>> configured component isnot being bounced due to a configuration change. >>>> The most likely suspect is that the component is simply not being used at >>>> that time, and so it is being disposed (DS lazy behaviour). This could >&
Re: [osgi-dev] Double config
On the topic of bouncing… What is a good way to test for robustness against this phenomenon? Is there some kind of Monkey Testing [1] framework to help with this? [1] https://en.wikipedia.org/wiki/Monkey_testing <https://en.wikipedia.org/wiki/Monkey_testing> > On Jul 12, 2018, at 23:11, Peter Kriens wrote: > > Well, OSGi has a tendency to punish short cuts. In the long run this is very > valuable, I’ve seen too many software disasters to sleep well at night. > However, for a developer behind his screen and a looming deadline the long > term goals are unfortunately not so urgent :-( > > Kind regards, > > Peter Kriens > > > >> On 12 Jul 2018, at 13:38, David Leangen via osgi-dev > <mailto:osgi-dev@mail.osgi.org>> wrote: >> >> >> As always, thank you VERY much to all of you for your great suggestions. I >> will look into this from tomorrow. I didn’t know the concept of “bouncing”. >> That is interesting. Now that I am aware, I will give more thought to it. >> >> One thing I have seen stated before on this list is that OSGi is indeed >> complex, but it is not accidental complexity. It is simply making complexity >> explicit, and providing the tools to work with complexity. I completely >> agree with this statement. >> >> I am still learning all the time, and am always amazed that there is still >> so much deeper to go. Thanks for helping me along this journey. >> >> >> Cheers, >> =David >> >> >> >>> On Jul 12, 2018, at 17:42, Fauth Dirk (AA-AS/EIS2-EU) via osgi-dev >>> mailto:osgi-dev@mail.osgi.org>> wrote: >>> >>> If it is a bouncing problem, than you could also try to configure the >>> behavior using the property >>> >>> ds.delayed.keepInstances=true >>> >>> From the Apache Felix documentation: >>> >>> Whether or not to keep instances of delayed components once they are not >>> referred to any more. The Declarative Services specifications suggests that >>> instances of delayed components are disposed off if there is not used any >>> longer. Setting this flag causes the components to not be disposed off and >>> thus prevent them from being constantly recreated if often used. Examples >>> of such components may be EventHandler services. The default is to dispose >>> off unused components. See FELIX-3039 >>> <https://issues.apache.org/jira/browse/FELIX-3039> for details. >>> >>> http://felix.apache.org/documentation/subprojects/apache-felix-service-component-runtime.html >>> >>> <http://felix.apache.org/documentation/subprojects/apache-felix-service-component-runtime.html> >>> >>> Equinox DS had this set by default, while the default in Felix SCR is >>> false. With the usage of Felix SCR in Eclipse we needed to explicitly set >>> this parameter to true so the previous behavior persists. >>> >>> Mit freundlichen Grüßen / Best regards >>> >>> Dirk Fauth >>> >>> Automotive Service Solutions, ESI application (AA-AS/EIS2-EU) >>> Robert Bosch GmbH | Postfach 11 29 | 73201 Plochingen | GERMANY | >>> www.bosch.com <http://www.bosch.com/> >>> Tel. +49 7153 666-1155 | dirk.fa...@de.bosch.com >>> <mailto:dirk.fa...@de.bosch.com> >>> >>> Sitz: Stuttgart, Registergericht: Amtsgericht Stuttgart, HRB 14000; >>> Aufsichtsratsvorsitzender: Franz Fehrenbach; Geschäftsführung: Dr. Volkmar >>> Denner, >>> Prof. Dr. Stefan Asenkerschbaumer, Dr. Michael Bolle, Dr. Rolf Bulander, >>> Dr. Stefan Hartung, Dr. Markus Heyn, >>> Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Peter Tyroller >>> >>> >>> Von: osgi-dev-boun...@mail.osgi.org <mailto:osgi-dev-boun...@mail.osgi.org> >>> [mailto:osgi-dev-boun...@mail.osgi.org >>> <mailto:osgi-dev-boun...@mail.osgi.org>] Im Auftrag von Tim Ward via >>> osgi-dev >>> Gesendet: Donnerstag, 12. Juli 2018 10:22 >>> An: Peter Kriens mailto:peter.kri...@aqute.biz>>; >>> OSGi Developer Mail List >> <mailto:osgi-dev@mail.osgi.org>> >>> Betreff: Re: [osgi-dev] Double config >>> >>> Hi David, >>> >>> >>> This is a gift! :-) It means your code is not handling the dynamics >>> correctly and now you know it! >>> >>> I’m not sure that there’s quite enough evidence to come to this conclusion. >>> It could simply be that everythin
Re: [osgi-dev] Double config
Well, OSGi has a tendency to punish short cuts. In the long run this is very valuable, I’ve seen too many software disasters to sleep well at night. However, for a developer behind his screen and a looming deadline the long term goals are unfortunately not so urgent :-( Kind regards, Peter Kriens > On 12 Jul 2018, at 13:38, David Leangen via osgi-dev > wrote: > > > As always, thank you VERY much to all of you for your great suggestions. I > will look into this from tomorrow. I didn’t know the concept of “bouncing”. > That is interesting. Now that I am aware, I will give more thought to it. > > One thing I have seen stated before on this list is that OSGi is indeed > complex, but it is not accidental complexity. It is simply making complexity > explicit, and providing the tools to work with complexity. I completely agree > with this statement. > > I am still learning all the time, and am always amazed that there is still so > much deeper to go. Thanks for helping me along this journey. > > > Cheers, > =David > > > >> On Jul 12, 2018, at 17:42, Fauth Dirk (AA-AS/EIS2-EU) via osgi-dev >> mailto:osgi-dev@mail.osgi.org>> wrote: >> >> If it is a bouncing problem, than you could also try to configure the >> behavior using the property >> >> ds.delayed.keepInstances=true >> >> From the Apache Felix documentation: >> >> Whether or not to keep instances of delayed components once they are not >> referred to any more. The Declarative Services specifications suggests that >> instances of delayed components are disposed off if there is not used any >> longer. Setting this flag causes the components to not be disposed off and >> thus prevent them from being constantly recreated if often used. Examples of >> such components may be EventHandler services. The default is to dispose off >> unused components. See FELIX-3039 >> <https://issues.apache.org/jira/browse/FELIX-3039> for details. >> >> http://felix.apache.org/documentation/subprojects/apache-felix-service-component-runtime.html >> >> <http://felix.apache.org/documentation/subprojects/apache-felix-service-component-runtime.html> >> >> Equinox DS had this set by default, while the default in Felix SCR is false. >> With the usage of Felix SCR in Eclipse we needed to explicitly set this >> parameter to true so the previous behavior persists. >> >> Mit freundlichen Grüßen / Best regards >> >> Dirk Fauth >> >> Automotive Service Solutions, ESI application (AA-AS/EIS2-EU) >> Robert Bosch GmbH | Postfach 11 29 | 73201 Plochingen | GERMANY | >> www.bosch.com <http://www.bosch.com/> >> Tel. +49 7153 666-1155 | dirk.fa...@de.bosch.com >> <mailto:dirk.fa...@de.bosch.com> >> >> Sitz: Stuttgart, Registergericht: Amtsgericht Stuttgart, HRB 14000; >> Aufsichtsratsvorsitzender: Franz Fehrenbach; Geschäftsführung: Dr. Volkmar >> Denner, >> Prof. Dr. Stefan Asenkerschbaumer, Dr. Michael Bolle, Dr. Rolf Bulander, Dr. >> Stefan Hartung, Dr. Markus Heyn, >> Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Peter Tyroller >> >> >> Von: osgi-dev-boun...@mail.osgi.org <mailto:osgi-dev-boun...@mail.osgi.org> >> [mailto:osgi-dev-boun...@mail.osgi.org >> <mailto:osgi-dev-boun...@mail.osgi.org>] Im Auftrag von Tim Ward via osgi-dev >> Gesendet: Donnerstag, 12. Juli 2018 10:22 >> An: Peter Kriens mailto:peter.kri...@aqute.biz>>; >> OSGi Developer Mail List > <mailto:osgi-dev@mail.osgi.org>> >> Betreff: Re: [osgi-dev] Double config >> >> Hi David, >> >> >> This is a gift! :-) It means your code is not handling the dynamics >> correctly and now you know it! >> >> I’m not sure that there’s quite enough evidence to come to this conclusion. >> It could simply be that everything is working fine with a static policy, and >> working the way that DS is supposed to. In general a DS component being >> bounced like this is nothing to worry about, it’s just a change rippling >> through the system, and it’s typically resolved in very short order. If you >> do want to reason about why, however, then there are several places to look. >> >> For some reason, the Component gets activated, deactivated, then activated >> again, which is not desirable. >> ... >> 1. How can I figure out why this is happening. I have tried many approaches, >> but can’t seem to get a clue as to why this is happening. Since it generally >> doesn’t seem to happen for other configured components, I am
Re: [osgi-dev] Double config
As always, thank you VERY much to all of you for your great suggestions. I will look into this from tomorrow. I didn’t know the concept of “bouncing”. That is interesting. Now that I am aware, I will give more thought to it. One thing I have seen stated before on this list is that OSGi is indeed complex, but it is not accidental complexity. It is simply making complexity explicit, and providing the tools to work with complexity. I completely agree with this statement. I am still learning all the time, and am always amazed that there is still so much deeper to go. Thanks for helping me along this journey. Cheers, =David > On Jul 12, 2018, at 17:42, Fauth Dirk (AA-AS/EIS2-EU) via osgi-dev > wrote: > > If it is a bouncing problem, than you could also try to configure the > behavior using the property > > ds.delayed.keepInstances=true > > From the Apache Felix documentation: > > Whether or not to keep instances of delayed components once they are not > referred to any more. The Declarative Services specifications suggests that > instances of delayed components are disposed off if there is not used any > longer. Setting this flag causes the components to not be disposed off and > thus prevent them from being constantly recreated if often used. Examples of > such components may be EventHandler services. The default is to dispose off > unused components. See FELIX-3039 > <https://issues.apache.org/jira/browse/FELIX-3039> for details. > > http://felix.apache.org/documentation/subprojects/apache-felix-service-component-runtime.html > > <http://felix.apache.org/documentation/subprojects/apache-felix-service-component-runtime.html> > > Equinox DS had this set by default, while the default in Felix SCR is false. > With the usage of Felix SCR in Eclipse we needed to explicitly set this > parameter to true so the previous behavior persists. > > Mit freundlichen Grüßen / Best regards > > Dirk Fauth > > Automotive Service Solutions, ESI application (AA-AS/EIS2-EU) > Robert Bosch GmbH | Postfach 11 29 | 73201 Plochingen | GERMANY | > www.bosch.com <http://www.bosch.com/> > Tel. +49 7153 666-1155 | dirk.fa...@de.bosch.com > <mailto:dirk.fa...@de.bosch.com> > > Sitz: Stuttgart, Registergericht: Amtsgericht Stuttgart, HRB 14000; > Aufsichtsratsvorsitzender: Franz Fehrenbach; Geschäftsführung: Dr. Volkmar > Denner, > Prof. Dr. Stefan Asenkerschbaumer, Dr. Michael Bolle, Dr. Rolf Bulander, Dr. > Stefan Hartung, Dr. Markus Heyn, > Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Peter Tyroller > > > Von: osgi-dev-boun...@mail.osgi.org [mailto:osgi-dev-boun...@mail.osgi.org] > Im Auftrag von Tim Ward via osgi-dev > Gesendet: Donnerstag, 12. Juli 2018 10:22 > An: Peter Kriens ; OSGi Developer Mail List > > Betreff: Re: [osgi-dev] Double config > > Hi David, > > > This is a gift! :-) It means your code is not handling the dynamics correctly > and now you know it! > > I’m not sure that there’s quite enough evidence to come to this conclusion. > It could simply be that everything is working fine with a static policy, and > working the way that DS is supposed to. In general a DS component being > bounced like this is nothing to worry about, it’s just a change rippling > through the system, and it’s typically resolved in very short order. If you > do want to reason about why, however, then there are several places to look. > > For some reason, the Component gets activated, deactivated, then activated > again, which is not desirable. > ... > 1. How can I figure out why this is happening. I have tried many approaches, > but can’t seem to get a clue as to why this is happening. Since it generally > doesn’t seem to happen for other configured components, I am assuming that it > is not a Configurator problem. > > From the rest of your email it is clear that the configured component > provides a service. This will make it lazy by default. You have also stated > that you’re using has a required configuration policy. Therefore it will only > be activated when: > > There is a configuration present > All of the mandatory services are satisfied > Someone is actually using the service > > The component will then be deactivated when any of these things are no-longer > true, and so this means that your component may be being bounced for several > reasons, only one of which is to do with configuration. > > While it seems unlikely to me, you seem to be fairly convinced that the > configuration is at fault so lets start there. > > Does the generated XML file in your bundle actually say that the > configuration is required. This is the configuration used by DS (not the
Re: [osgi-dev] Double config
If it is a bouncing problem, than you could also try to configure the behavior using the property ds.delayed.keepInstances=true From the Apache Felix documentation: Whether or not to keep instances of delayed components once they are not referred to any more. The Declarative Services specifications suggests that instances of delayed components are disposed off if there is not used any longer. Setting this flag causes the components to not be disposed off and thus prevent them from being constantly recreated if often used. Examples of such components may be EventHandler services. The default is to dispose off unused components. See FELIX-3039<https://issues.apache.org/jira/browse/FELIX-3039> for details. http://felix.apache.org/documentation/subprojects/apache-felix-service-component-runtime.html Equinox DS had this set by default, while the default in Felix SCR is false. With the usage of Felix SCR in Eclipse we needed to explicitly set this parameter to true so the previous behavior persists. Mit freundlichen Grüßen / Best regards Dirk Fauth Automotive Service Solutions, ESI application (AA-AS/EIS2-EU) Robert Bosch GmbH | Postfach 11 29 | 73201 Plochingen | GERMANY | www.bosch.com<http://www.bosch.com> Tel. +49 7153 666-1155 | dirk.fa...@de.bosch.com<mailto:dirk.fa...@de.bosch.com> Sitz: Stuttgart, Registergericht: Amtsgericht Stuttgart, HRB 14000; Aufsichtsratsvorsitzender: Franz Fehrenbach; Geschäftsführung: Dr. Volkmar Denner, Prof. Dr. Stefan Asenkerschbaumer, Dr. Michael Bolle, Dr. Rolf Bulander, Dr. Stefan Hartung, Dr. Markus Heyn, Dr. Dirk Hoheisel, Christoph Kübel, Uwe Raschke, Peter Tyroller Von: osgi-dev-boun...@mail.osgi.org [mailto:osgi-dev-boun...@mail.osgi.org] Im Auftrag von Tim Ward via osgi-dev Gesendet: Donnerstag, 12. Juli 2018 10:22 An: Peter Kriens ; OSGi Developer Mail List Betreff: Re: [osgi-dev] Double config Hi David, This is a gift! :-) It means your code is not handling the dynamics correctly and now you know it! I’m not sure that there’s quite enough evidence to come to this conclusion. It could simply be that everything is working fine with a static policy, and working the way that DS is supposed to. In general a DS component being bounced like this is nothing to worry about, it’s just a change rippling through the system, and it’s typically resolved in very short order. If you do want to reason about why, however, then there are several places to look. For some reason, the Component gets activated, deactivated, then activated again, which is not desirable. ... 1. How can I figure out why this is happening. I have tried many approaches, but can’t seem to get a clue as to why this is happening. Since it generally doesn’t seem to happen for other configured components, I am assuming that it is not a Configurator problem. From the rest of your email it is clear that the configured component provides a service. This will make it lazy by default. You have also stated that you’re using has a required configuration policy. Therefore it will only be activated when: * There is a configuration present * All of the mandatory services are satisfied * Someone is actually using the service The component will then be deactivated when any of these things are no-longer true, and so this means that your component may be being bounced for several reasons, only one of which is to do with configuration. While it seems unlikely to me, you seem to be fairly convinced that the configuration is at fault so lets start there. 1. Does the generated XML file in your bundle actually say that the configuration is required. This is the configuration used by DS (not the annotations) at runtime. It’s unlikely that this has gone wrong, but it’s an easy check 2. Do you have more than one way of putting configuration into the runtime? If you are also using File Install, or some other configuration management agent, then it’s entirely possible that you’re seeing a configuration update occurring. 3. Do you have multiple configuration bundles which both contain a configuration for this component? The configurator will process these one at a time, and it will result in configuration bouncing 4. Is it possible that something is forcing a re-resolve of your configuration bundle or the configurator? This could easily trigger the configurations to be reprocessed. Now in my view the most likely reason for this behaviour is that the configured component is not being bounced due to a configuration change. The most likely suspect is that the component is simply not being used at that time, and so it is being disposed (DS lazy behaviour). This could easily happen if one of the dependent services that you mention starts using your component, and then is bounced (by a configuration update or whatever) which causes your component to be released. If nobody else is using your component at the time then it will b
Re: [osgi-dev] Double config
Hi David, > This is a gift! :-) It means your code is not handling the dynamics correctly > and now you know it! I’m not sure that there’s quite enough evidence to come to this conclusion. It could simply be that everything is working fine with a static policy, and working the way that DS is supposed to. In general a DS component being bounced like this is nothing to worry about, it’s just a change rippling through the system, and it’s typically resolved in very short order. If you do want to reason about why, however, then there are several places to look. >> For some reason, the Component gets activated, deactivated, then activated >> again, which is not desirable. >> ... >> 1. How can I figure out why this is happening. I have tried many approaches, >> but can’t seem to get a clue as to why this is happening. Since it generally >> doesn’t seem to happen for other configured components, I am assuming that >> it is not a Configurator problem. From the rest of your email it is clear that the configured component provides a service. This will make it lazy by default. You have also stated that you’re using has a required configuration policy. Therefore it will only be activated when: There is a configuration present All of the mandatory services are satisfied Someone is actually using the service The component will then be deactivated when any of these things are no-longer true, and so this means that your component may be being bounced for several reasons, only one of which is to do with configuration. While it seems unlikely to me, you seem to be fairly convinced that the configuration is at fault so lets start there. Does the generated XML file in your bundle actually say that the configuration is required. This is the configuration used by DS (not the annotations) at runtime. It’s unlikely that this has gone wrong, but it’s an easy check Do you have more than one way of putting configuration into the runtime? If you are also using File Install, or some other configuration management agent, then it’s entirely possible that you’re seeing a configuration update occurring. Do you have multiple configuration bundles which both contain a configuration for this component? The configurator will process these one at a time, and it will result in configuration bouncing Is it possible that something is forcing a re-resolve of your configuration bundle or the configurator? This could easily trigger the configurations to be reprocessed. Now in my view the most likely reason for this behaviour is that the configured component is not being bounced due to a configuration change. The most likely suspect is that the component is simply not being used at that time, and so it is being disposed (DS lazy behaviour). This could easily happen if one of the dependent services that you mention starts using your component, and then is bounced (by a configuration update or whatever) which causes your component to be released. If nobody else is using your component at the time then it will be deactivated and released. The easiest way to verify this is to make your component immediate. This will remove the laziness, and you will get a good idea as to whether the bounce is caused by things that you depend on, or by things that depend on you. If making your component immediate removes the “problem” then it proves that this isn’t a problem at all (and you can then remove the immediate behaviour again). If making your component immediate doesn’t stop the bouncing then the third set of things to check is the list of services that your component depends on. Is it possible that one of them is being bounced due to a configuration update, or perhaps one of their service dependencies being unregistered/re-registered? As I mentioned before, bouncing of DS components is simply the way that updates propagate through the system when services use a static policy. It isn’t inherently a bad thing, but if you want to avoid it you have to be dynamic all the way down the dependency graph. Usually this is a lot more effort than it’s worth! I hope this helps, Tim > On 12 Jul 2018, at 08:39, Peter Kriens via osgi-dev > wrote: > > This is a gift! :-) It means your code is not handling the dynamics correctly > and now you know it! > > The cause is that that the DS starts the components before the Configurator > has done its work. The easiest solution seems to be to use start levels. If > your code CAN handle the dynamics, then this is one of the few legitimate > places where startlevels are useful. I usually oppose it because people do > not handle the dynamics correctly and want a short cut. This is fine until it > is not. And the ‘not’ happens guaranteed one day. So first fix the dynamics, > and then think of solutions that improve the experience. > > For this purpose, enRoute Classic had a > ‘osgi.enroute.configurer.api.ConfigurationDone’ service. If you made an > @Reference to C
Re: [osgi-dev] Double config
This is a gift! :-) It means your code is not handling the dynamics correctly and now you know it! The cause is that that the DS starts the components before the Configurator has done its work. The easiest solution seems to be to use start levels. If your code CAN handle the dynamics, then this is one of the few legitimate places where startlevels are useful. I usually oppose it because people do not handle the dynamics correctly and want a short cut. This is fine until it is not. And the ‘not’ happens guaranteed one day. So first fix the dynamics, and then think of solutions that improve the experience. For this purpose, enRoute Classic had a ‘osgi.enroute.configurer.api.ConfigurationDone’ service. If you made an @Reference to ConfigurationDone then you were guaranteed to not start before the Configurer had done its magic. Since you did not want to depend on such a specific service for reasons of cohesion, I developed AggregateState. One of the aggregated states was then the presence of the ConfigurationDone service. Although this is also not perfectly cohesive it at least aggregates all the uncohesive things in one place and it is configurable. Although this works the customer still is not completely happy since also the Aggregate State feels uncohesive. So we’ve been discussing a new angle. I want to try to make the Configuration Records _transient_. In Felix Config Admin you can provide a persistence service (and it was recently made useful). I was thinking of setting a special property in the configuration (something like ‘:persistence:transient’). The persistence layer would then _not_ persist it. I.e. after a restart there would be no configuration until the Configurer sets it. This will (I expect) seriously diminish the bouncing caused for these kind of components. And if you’re asking why I am still on the enRoute classic Configurer. Well, it has ‘precious’ fields and they solved a nasty problem. We needed to use a well defined value but if the user set one of those values, we wanted to keep the user’s value. Quite a common scenario. With `precious` fields you rely on default values (so no value for a precious field in the configurer’s input) but copy the previous value to the newer configuration, if present. Works quite well. I think `transient` and `precious` could be nice extensions to the new Configurator for R8. Hope this helps. Kind regards, Peter Kriens > On 12 Jul 2018, at 00:48, David Leangen via osgi-dev > wrote: > > > Hi! > > A question about component configuration. > > I have a component that has a required configuration policy. Using a (pre R7) > Configurator to configure the component. For some reason, the Component gets > activated, deactivated, then activated again, which is not desirable. > > Questions: > > 1. How can I figure out why this is happening. I have tried many approaches, > but can’t seem to get a clue as to why this is happening. Since it generally > doesn’t seem to happen for other configured components, I am assuming that it > is not a Configurator problem. > > 2. Is there a way to prohibit this from happening? > > > In the meantime, I will make the dependent services more dynamic so they are > not thrown off by this change, but their behavior is actually correct: the > expectation is that the configured service should only get instantiated once, > so a static @Reference is correct. > > > Thanks! > =David > > > ___ > OSGi Developer Mail List > osgi-dev@mail.osgi.org > https://mail.osgi.org/mailman/listinfo/osgi-dev ___ OSGi Developer Mail List osgi-dev@mail.osgi.org https://mail.osgi.org/mailman/listinfo/osgi-dev
[osgi-dev] Double config
Hi! A question about component configuration. I have a component that has a required configuration policy. Using a (pre R7) Configurator to configure the component. For some reason, the Component gets activated, deactivated, then activated again, which is not desirable. Questions: 1. How can I figure out why this is happening. I have tried many approaches, but can’t seem to get a clue as to why this is happening. Since it generally doesn’t seem to happen for other configured components, I am assuming that it is not a Configurator problem. 2. Is there a way to prohibit this from happening? In the meantime, I will make the dependent services more dynamic so they are not thrown off by this change, but their behavior is actually correct: the expectation is that the configured service should only get instantiated once, so a static @Reference is correct. Thanks! =David ___ OSGi Developer Mail List osgi-dev@mail.osgi.org https://mail.osgi.org/mailman/listinfo/osgi-dev
