dependencymanager/docs/whatsnew.mdtext - onos-felix - Gitiles

 # What's new in DependencyManager 4.0

 DependencyManager 4.0 has been significantly reworked to improve support for concurrency. The following principles form the basis of the new concurrency model in DM4.

  * All external events that influence the state of dependencies are recorded and given to the serial executor of the component. We record whatever data comes in, so when the actual job is run by the serial executor, we still have access to the original data without having to access other sources whose state might have changed since.
  * The serial executor of a component will execute a job immediately if it is being called by the thread that is already executing jobs.
  * If the serial executor of a component had not yet started a job, it will queue and start it on the current thread.
  * If the serial executor gets invoked from a different thread than the one currently executing jobs, the job will be put at the end of the queue. As mentioned before, any data associated with the event will also be recorded so it is available when the job executes.
  * State in the component and dependency can only be modified via the serial executor thread. This means we don't need explicit synchronization anywhere.

 DependencyManager 4 now also supports parallel execution of component wiring.

 Added support for parallelism: To allow components to be started and handled in parallel, you can now register in the OSGi service registry a ComponentExecutorFactory service that is used to get an Executor for the management of all components dependencies/lifecycle callbacks. See javadoc from the org.apache.felix.dm.ComponentExecutorFactory interface for more information.

 You can also take a look at the the org.apache.felix.dependencymanager.samples project, which is registering a ComponentExecutorFactory from org.apache.felix.dependencymanager.samples.tpool bundle.

 See also the following property in the org.apache.felix.dependencymanager.samples/bnd.bnd

 	org.apache.felix.dependencymanager.parallel=\
 		'!org.apache.felix.dependencymanager.samples.tpool, *',\

 Here, all components will be handled by Executors provided by the ComponentExecutorFactory, except those having a package starting with "org.apache.felix.dependencymanager.samples.tpool" (because the threadpool is itself defined using the Dependency Manager API).
	# What's new in DependencyManager 4.0

	DependencyManager 4.0 has been significantly reworked to improve support for concurrency. The following principles form the basis of the new concurrency model in DM4.

	* All external events that influence the state of dependencies are recorded and given to the serial executor of the component. We record whatever data comes in, so when the actual job is run by the serial executor, we still have access to the original data without having to access other sources whose state might have changed since.
	* The serial executor of a component will execute a job immediately if it is being called by the thread that is already executing jobs.
	* If the serial executor of a component had not yet started a job, it will queue and start it on the current thread.
	* If the serial executor gets invoked from a different thread than the one currently executing jobs, the job will be put at the end of the queue. As mentioned before, any data associated with the event will also be recorded so it is available when the job executes.
	* State in the component and dependency can only be modified via the serial executor thread. This means we don't need explicit synchronization anywhere.

	DependencyManager 4 now also supports parallel execution of component wiring.

	Added support for parallelism: To allow components to be started and handled in parallel, you can now register in the OSGi service registry a ComponentExecutorFactory service that is used to get an Executor for the management of all components dependencies/lifecycle callbacks. See javadoc from the org.apache.felix.dm.ComponentExecutorFactory interface for more information.

	You can also take a look at the the org.apache.felix.dependencymanager.samples project, which is registering a ComponentExecutorFactory from org.apache.felix.dependencymanager.samples.tpool bundle.

	See also the following property in the org.apache.felix.dependencymanager.samples/bnd.bnd

	org.apache.felix.dependencymanager.parallel=\
	'!org.apache.felix.dependencymanager.samples.tpool, *',\

	Here, all components will be handled by Executors provided by the ComponentExecutorFactory, except those having a package starting with "org.apache.felix.dependencymanager.samples.tpool" (because the threadpool is itself defined using the Dependency Manager API).