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From Christoph Gritschenberger <christoph.gritschenber...@gmail.com>
Subject Telling whether startup is really complete
Date Wed, 08 Aug 2012 18:43:57 GMT
Hi,

I had another meeting with a customer today who asked me: "How can I
tell whether it is started up completely?". ("It" being our karaf-based
product)

So I had a look at several alternatives how I could accomplish this and
had an idea I wanted to discuss.

I know that I can modify the Start-level of the Shell-bundle but I don't
think that's enough.
Recently Christian Schneider implemented something to delay the startup
of the shell until all bundles are active. I think that's a good start,
but does not solve the problem completely for me. I encountered several
issues with the approach:

1. There is a short delay between the point where all karaf-base-bundles
are loaded and the feature-installer starts installing features
specified in "featuresBoot". When starting up the first time, this
almost always happens

...
	[  45] [    Active] [    5] OPS4J Base - Lang (1.3.0)
	[  46] [  Resolved] [   20] Apache Aries Blueprint Core Compatiblity
Fragment Bundle (1.0.0), Hosts: 26
	[  47] [    Active] [   30] Apache Karaf :: System :: Shell Commands
(3.0.0.SNAPSHOT)
	[  48] [    Active] [   24] Apache Karaf :: Deployer :: Spring
(3.0.0.SNAPSHOT)
	karaf@root()>

After a few seconds the installing of the features commences:

...
	[  47] [    Active] [   30] Apache Karaf :: System :: Shell Commands
(3.0.0.SNAPSHOT)
	[  48] [    Active] [   24] Apache Karaf :: Deployer :: Spring
(3.0.0.SNAPSHOT)
	[  49] [ Installed] [   30] Apache Karaf :: ConfigAdmin :: Core
(3.0.0.SNAPSHOT)
	[  50] [ Installed] [   30] Apache Karaf :: ConfigAdmin :: Commands
(3.0.0.SNAPSHOT)
...

So the condition "all non-fragment bundles are ACTIVE" does not
necessarily mean "startup is complete".

2. Even if all features are installed completely and all bundles are
ACTIVE, they may contain a blueprint-file and the blueprint-container
might take even longer to start up.


So I had an idea, I wanted to discuss:
How about introducing an additional interface (like "StartupIndicator"
with a method "boolean isStartupComplete()" or "int
getStartupProgress()"). The FeatureService could implement this
interface and provide the Service be registered with this additional
interface.
The Shell-bundle could then pick up all "StartupIndicator"-services and
require all of them to return true before actually showing the prompt.
Another StartupIndicator could check for BlueprintContainers to be
available.

This way, the shell would not actually have a direct dependency to the
FeatureService, but could delay the prompt until all features are
installed and active.

Another advantage is, that users would be able to implement their own
"StartupIndicator"-services to introduce even more delays.

WDYT?

kind regards,
christoph


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