Is that true of all extension of the
org.eclipse.core.runtime.applications extension point, that they don’t
start until the platform has been initialized? Even when they run in any
thread and not just the main?
I would be happy enough to be able to say:
if you declare your services in this way, we will wait for those to be
initialized before we start, otherwise we won’t guarantee your service
will be available. I was hopping to be able to do that through DS, so waiting
for the DS thread to stop seems fine, although it would be nice to have a more
formal way to do this, through public API.
In our application, we don’t expect
bundles to be started and stopped dynamically (at least not too often), so we
are really only worried about knowing what services there are at the initial
startup.
I was trying to figure out a good way to
safeguard against the dynamism of the services. I don’t think there
is an issue with the services which require 0..1 or 1..1 instances of another service,
but I don’t know what to do about the services which require 0..n and
1..n because you don’t really know how many more services there might be
without doing what DS seems to already do, look through the manifests and find the
declared services. I suppose you could also wait for the platform to stop
starting bundles, but then DS could still be running so I’d still need a
way to know when it was done.
Thanks,
Otto
From:
equinox-dev-bounces@xxxxxxxxxxx [mailto:equinox-dev-bounces@xxxxxxxxxxx] On Behalf Of Thomas Watson
Sent: Wednesday, September 03,
2008 1:30 PM
To: Equinox development mailing
list
Subject: RE: [equinox-dev] When is
DS done loading services?
I think part of the problem here is the term
"application". In this case we are talking about an RCP application
which is defined as an Eclipse extension to the org.eclipse.core.runtime.applications
extension point. When launching Eclipse the default application is started
after the platform has been initialized and the start-level has reached the
final state.
RCP applications have historically depended on the platform to be "fully
booted" and ready before their application is started. This mentality does
not mix well with the dynamic nature of OSGi services. When DS is added to the
mix the boot sequence become less predictable because services are not
registered synchronously as bundles get started during the bootup process
(incrementing the start-level). Currently the Eclipse application container
just assumes the application is ready to launch after the the platform has been
initialized and the final start-level has been reached.
To work around the issue you will need to do something like BJ says and make
the application handle dynamic service registrations. The problem you will run
into is that the Eclipse application container has no idea that your Eclipse
application depends on services before it is ready to launch. So in addition to
making your application handle dynamic services, you will also need to handle
waiting for your "required" services to be available in your
application start method before allowing your application start method to
continue to bring up your application. Or you can simply allow your application
to start and put safeguards in to handle when a service is not available yet.
It would be great if we could figure out a better way to mix the use of
extensions and services together in an Eclipse application.
Tom
BJ
Hargrave---09/03/2008 02:04:43 PM---But even DS only knows about started
bundles. If a bundle is started after DS has processed some bundle, then new
services can
|
From:
|
BJ
Hargrave/Austin/IBM@IBMUS
|
|
To:
|
Equinox development
mailing list <equinox-dev@xxxxxxxxxxx>
|
|
Date:
|
09/03/2008 02:04 PM
|
|
Subject:
|
RE: [equinox-dev]
When is DS done loading services?
|
But even DS only knows about started bundles. If a bundle is started after DS
has processed some bundle, then new services can be registered. There is no way
for DS to know about all possible services being ready since some may come from
bundles yet to be started. The best DS could tell you is that it is done
processing services from bundles that are currently started.
It is far better in the long run for the application to handle dynamism.
Anything you do today to try and enforce some ordering will likely fail in the
future when some thing changes about the set of installed bundles.
--
|
From:
|
"Cortez, Otto"
<OttoCortez@xxxxxxxxxxxxx>
|
|
To:
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"Equinox development mailing list" <equinox-dev@xxxxxxxxxxx>
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Date:
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2008/09/03 02:48 PM
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Subject:
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RE: [equinox-dev] When is DS done loading services?
|
It is more important for us to know what functionality is installed and
available before parts of the application execute then it is for us to support
dynamism. I would like to keep the dynamism if we can, but to do that and
provide reliable execution I think the application would need to guarantee that
all services known through the bundle manifests will be initialized before we
start processing. I guess using extensions might be a better fit.
I’m not sure if we need DS to synchronously register services as much as
some way to listen to DS events or know its state, like is it just sitting
around waiting for more bundles to be activated or deactivated. I was focused
on services being managed by DS since I thought DS would know weather it was
done initializing all services listed in the active bundles’ manifest
files and then we would be able to say to users which may supply functionality,
well if you use DS then we could guarantee that we wouldn’t start until
DS had initialized your services.
Thanks,
Otto
From:
equinox-dev-bounces@xxxxxxxxxxx [mailto:equinox-dev-bounces@xxxxxxxxxxx] On Behalf Of BJ Hargrave
Sent: Wednesday, September 03, 2008 7:22 AM
To: Equinox development mailing list
Subject: Re: [equinox-dev] When is DS done loading services?
The whole point of services is that the are dynamic. The fact the DS is
"processing" them on behalf of some bundle does not mean that another
bundle should know or observe that.
Bundles which depend upon a service need to deal with that service's dynamism.
You can't assume a bundle's activator or starting a bundle will synchronously
register some services. I would not support an option for DS to synchronously
register services during bundle start as this means people will improperly use
that.
You may also be seeing an impedance mismatch between the lifecycle of
extensions and services. Extensions become active when the bundle is resolved
while services become active only when the bundle is started. Switching to use
extensions will not allow for dynamism (unless you want to write all the code
to use the extension registry API to do so.)
You may be able to use startlevels to mitigate the issue (make sure all bundles
providing service B are started before bundles using B), but this is also a
hack. It would be better if service A dealt with the dynamics of service B such
that service A has a dynamic dependency on service B and is able to accept B's
being registered and unregistered at any time.
--
|
From:
|
Stoyan Boshev <s.boshev@xxxxxxxxxxx>
|
|
To:
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Equinox development mailing list <equinox-dev@xxxxxxxxxxx>
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Date:
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2008/09/03 07:51 AM
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Subject:
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Re: [equinox-dev] When is DS done loading services?
|
Hi Otto,
I guess your problem is connected to the asynchronous processing of the
DS services.
As far as I understand the situation is: your application bundles are
started, then your application is started but at this moment not all of
the DS services are inited yet because they are being asynchronously
processed.
Unfortunately currently there is no way to find out when DS completes
the DS services processing.
I think if there was an option that DS bundle process the DS services in
the started bundles synchronously, it would solve your problem. So I
will open bug(enhancement) about that and hopefully this will be
implemented soon.
As a possible workaround you could observe the running threads and when
the thread with name "Component Resolve Thread" disappears this would
mean that DS bundle has no more work to do and eventually all of your DS
services are processed. I realize this is not a clean solution (that's
why I call it workaround) but at this moment I cannot find out a more
appropriate working solution without modifications in the DS bundle.
Stoyan
Cortez, Otto wrote:
> I made a post to the Eclipse newcomers group a few weeks ago, but did
> not get a response. I don’t know if this is the appropriate place
for
> this question, but hopefully someone can point me in the right direction.
>
>
>
> We are building a headless RCP application and we would like to use DS
> to make functionality available. The problem we are running into is
> that not all of the services we declared through DS get loaded and are
> visible before our application executes.
>
>
>
> For example, I have a service A which needs 0..n instances of another
> service B. The issue I'm running into is that if the implementations of
> service B are spread across several bundles, then the service A will not
> have seen all instances of service B when it is called since the
> application starts (and sometimes ends) running before DS is done
> looking through all the bundles and registering all the services in the
> active bundles.
>
> Is there a way to know when declarative services is done looking through
> the active bundles and loading the services found in them? Am I missing
> something?
>
>
>
> It seems that using the plug-in registry may solve this issue. Is that
> perhaps a better way to go?
>
>
>
> Thanks,
> Otto
>
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--
---------------------------------------------------------
dipl. eng. Stoyan Boshev . Department manager
ProSyst Labs EOOD
1606 Sofia, Bulgaria . 48 Vladajska Str.
Tel. +359 2 953 05 88; Fax +359 2 953 26 17
Mobile: +359 88
898 29 17
http://www.prosyst.com .
s.boshev@xxxxxxxxxxx
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