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Architecture introspection is required when the system doesn't work as expected. In this case, having a quick access to instances states and interconnection is a stringent requirement. The arch command allows getting these data from the Felix Shell and , from the Equinox shell and Gogo.

Note : The Gogo commands are not yet released but are available from the iPOJO trunk.

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Download

The Felix command commands is available from the download page and in the arch folder of the iPOJO trunk http://svn.apache.org/repos/asf/felix/trunk/ipojo/arch/.
The Equinox command sources are available http://svn.apache.org/repos/asf/felix/sandbox/clement/ipojo-utils/arch-equinox/. To compile sources, just launch the mvn clean install and deploy the resulting bundle.

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Installation

Once you get the bundle, just install and start it in the OSGi Framework shell:

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install file:/BUNDLE_URL.jar
Bundle X installed
start X

install file:/ARCH_GOGO_URL.jar
Bundle X installed
start X

Equinox and Felix Shells

Then, you can use it to introspect the system by launching the arch command.

arch => displays instances name & state (equivalent to arch \-instances)
arch -instance $instance_name => displays complete information about the instance $instance_name
arch -factories => display the list of available factories
arch -factory $factory_name => display complete information about the factory $factory_name
arch -handlers => list available handlers

Gogo Shell Commands

The set of commands available from Gogo is a little bit different:

• ipojo:instances (or just instances) lists the instances and state
• ipojo:instance $instance_name (or just instance $instance_name) displays the complete information about the specified $instance_name
• ipojo:factories (or just factories) lists the available public factories
• ipojo:factory $factory_name (or just factory $factory_name) displays complete information about the factory $factory_name
• ipojo:handlers (or just handlers lists available handlers

Reading instance architecture

When you launch the arch command (or instances on Gogo), the list of created instances (enabling architecture introspection) is displayed.

-> arch
Instance ArchCommand -> valid
Instance spell.english.EnglishDictionary-0 -> valid
Instance spell.checker.SpellCheck-0 -> valid
Instance spell.gui.SpellCheckerGui-0 -> valid

$ instances
Instance ArchCommand -> valid
Instance spell.english.EnglishDictionary-0 -> valid
Instance spell.checker.SpellCheck-0 -> valid
Instance spell.gui.SpellCheckerGui-0 -> valid

To get more information on an instance, launch arch -instance the_instance_name (or instance the_instance_name on Gogo)

-> arch -instance spell.checker.SpellCheck-0                                    
instance component.type="spell.checker.SpellCheck" state="valid" bundle="8" name="spell.checker.SpellCheck-0"
	handler state="valid" name="org.apache.felix.ipojo.handlers.dependency.DependencyHandler"
		requires optional="false" aggregate="false" state="resolved" binding-policy="dynamic" specification="spell.services.DictionaryService"
	handler state="valid" name="org.apache.felix.ipojo.handlers.providedservice.ProvidedServiceHandler"
		provides service.id="36" state="registered" specifications="[spell.services.SpellChecker]"
			property value="spell.checker.SpellCheck" name="factory.name"
			property value="spell.checker.SpellCheck-0" name="instance.name"
	handler state="valid" name="org.apache.felix.ipojo.handlers.architecture.ArchitectureHandler"

$ipojo:instance spell.checker.SpellCheck-0                                    
instance component.type="spell.checker.SpellCheck" state="valid" bundle="8" name="spell.checker.SpellCheck-0"
	handler state="valid" name="org.apache.felix.ipojo.handlers.dependency.DependencyHandler"
		requires optional="false" aggregate="false" state="resolved" binding-policy="dynamic" specification="spell.services.DictionaryService"
	handler state="valid" name="org.apache.felix.ipojo.handlers.providedservice.ProvidedServiceHandler"
		provides service.id="36" state="registered" specifications="[spell.services.SpellChecker]"
			property value="spell.checker.SpellCheck" name="factory.name"
			property value="spell.checker.SpellCheck-0" name="instance.name"
	handler state="valid" name="org.apache.felix.ipojo.handlers.architecture.ArchitectureHandler"

Instance architecture is organized as follows:
On the first line, are displayed the component type (i.e. factory), the instance state (valid or invalid), the bundle from which the instance is created, and the instance name.
Then, the information is organized handler by handler (a piece of container). For each handler plugged on the instance can participate to the instance architecture. For each handler its name (such as {{ org.apache.felix.ipojo.handlers.dependency.DependencyHandler}} for iPOJO service dependencies, {{ org.apache.felix.ipojo.handlers.providedservice.ProvidedServiceHandler}} for iPOJO service providing...) and the state (either valid or invalid are displayed. Remember that an instance is valid only and only if all plugged handlers are valid.
The org.apache.felix.ipojo.handlers.dependency.DependencyHandler provides data on service dependencies and more precisely on the state of service dependencies. In the previous example, the dependency on {{ spell.services.DictionaryService}} was resolved. On the following example, the same dependency is no more resolved:

instance component.type="spell.checker.SpellCheck" state="invalid" bundle="8" name="spell.checker.SpellCheck-0"
	handler state="invalid" name="org.apache.felix.ipojo.handlers.dependency.DependencyHandler"
		requires optional="false" aggregate="false" state="unresolved" binding-policy="dynamic" specification="spell.services.DictionaryService"
	handler state="valid" name="org.apache.felix.ipojo.handlers.providedservice.ProvidedServiceHandler"
		provides state="unregistered" specifications="[spell.services.SpellChecker]"
			property value="spell.checker.SpellCheck" name="factory.name"
			property value="spell.checker.SpellCheck-0" name="instance.name"
	handler state="valid" name="org.apache.felix.ipojo.handlers.architecture.ArchitectureHandler" 

Notes that, the instance also becomes invalid and that the provided service is unregistered.
If the provider comes back, the dependency becomes resolved and the instance becomes valid
If an instance begins to use a service, the bound providers are described in the instance architecture:

-> arch -instance spell.checker.SpellCheck-0 
instance component.type="spell.checker.SpellCheck" state="valid" bundle="8" name="spell.checker.SpellCheck-0"
	object name="spell.checker.SpellCheck@e222eb"
	handler state="valid" name="org.apache.felix.ipojo.handlers.dependency.DependencyHandler"
		requires optional="false" aggregate="false" state="resolved" binding-policy="dynamic" specification="spell.services.DictionaryService"
			uses service.id="41" instance.name="spell.english.EnglishDictionary-0"
	handler state="valid" name="org.apache.felix.ipojo.handlers.providedservice.ProvidedServiceHandler"
		provides service.id="42" state="registered" specifications="[spell.services.SpellChecker]"
			property value="spell.checker.SpellCheck" name="factory.name"
			property value="spell.checker.SpellCheck-0" name="instance.name"
	handler state="valid" name="org.apache.felix.ipojo.handlers.architecture.ArchitectureHandler"

$instance spell.checker.SpellCheck-0 
instance component.type="spell.checker.SpellCheck" state="valid" bundle="8" name="spell.checker.SpellCheck-0"
	object name="spell.checker.SpellCheck@e222eb"
	handler state="valid" name="org.apache.felix.ipojo.handlers.dependency.DependencyHandler"
		requires optional="false" aggregate="false" state="resolved" binding-policy="dynamic" specification="spell.services.DictionaryService"
			uses service.id="41" instance.name="spell.english.EnglishDictionary-0"
	handler state="valid" name="org.apache.felix.ipojo.handlers.providedservice.ProvidedServiceHandler"
		provides service.id="42" state="registered" specifications="[spell.services.SpellChecker]"
			property value="spell.checker.SpellCheck" name="factory.name"
			property value="spell.checker.SpellCheck-0" name="instance.name"
	handler state="valid" name="org.apache.felix.ipojo.handlers.architecture.ArchitectureHandler"

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To list available factories (i.e. component types), launch the arch -factories command (or factories on Gogo):

-> arch -factories
Factory spell.checker.SpellCheck (VALID)
Factory spell.gui.SpellCheckerGui (VALID)
Factory spell.english.EnglishDictionary (VALID)

$factories
Factory spell.checker.SpellCheck (VALID)
Factory spell.gui.SpellCheckerGui (VALID)
Factory spell.english.EnglishDictionary (VALID)

For each available (public) factories,the name and the sate are displayed. A factory is valid if and only if all required handlers are available. To get more information on a factory launch the arch -factory factory_name (or factory factory_name on Gogo) command:

factory implementation-class="spell.english.EnglishDictionary" state="valid" bundle="7" name="spell.english.EnglishDictionary"
	provides specification="spell.services.DictionaryService"
	missinghandlers list="[]"
	requiredhandlers list="[org.apache.felix.ipojo:provides, org.apache.felix.ipojo:architecture]"

On the first line, you get the implementation class of the type, the state of the factory, the bundle declaring the type and the name of the type. Then you You also get the list of required and missing handlers.

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You can also list available handlers with the arch -handlers (or handlers on Gogo) command.

-> arch -handlers
Handler org.apache.felix.ipojo:controller (VALID)
Handler org.apache.felix.ipojo:callback (VALID)
Handler org.apache.felix.ipojo:requires (VALID)
Handler org.apache.felix.ipojo:provides (VALID)
Handler org.apache.felix.ipojo:properties (VALID)
Handler org.apache.felix.ipojo:architecture (VALID)
Handler org.apache.felix.ipojo.handler.whiteboard:wbp (VALID)

$handlers
Handler org.apache.felix.ipojo:controller (VALID)
Handler org.apache.felix.ipojo:callback (VALID)
Handler org.apache.felix.ipojo:requires (VALID)
Handler org.apache.felix.ipojo:provides (VALID)
Handler org.apache.felix.ipojo:properties (VALID)
Handler org.apache.felix.ipojo:architecture (VALID)
Handler org.apache.felix.ipojo.handler.whiteboard:wbp (VALID)

Handlers with the org.apache.felix.ipojo namespace (section before :) are core handlers (provided by the iPOJO bundlecore bundles). Others are external handlers (provided by others bundles).