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https://issues.apache.org/jira/browse/FELIX-5114?page=com.atlassian.jira.plugin.system.issuetabpanels:all-tabpanel
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Pierre De Rop closed FELIX-5114.
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> Schedule configuration update in Component executor synchronously
> -----------------------------------------------------------------
>
> Key: FELIX-5114
> URL: https://issues.apache.org/jira/browse/FELIX-5114
> Project: Felix
> Issue Type: Improvement
> Components: Dependency Manager
> Affects Versions: org.apache.felix.dependencymanager-r5
> Reporter: Pierre De Rop
> Assignee: Pierre De Rop
> Priority: Minor
> Fix For: org.apache.felix.dependencymanager-r6
>
>
> Currently, all external events are handled through the Component queue
> (Executor). This allows to provide a nice thread model, where no
> synchronization is required inside DM, and also the user benefits from this
> because, because all component lifecycle callbacks and all dependency
> injections are also performed using the internal Component queue. So, in some
> situation, this model make life easier for the developer.
> But there is an exception to all this: the Configuration Dependency is
> currently handled from the Configuration Admin dispatcher thread, in other
> words, a component update callback can be called while a component "bind"
> method is called from another thread (if a service dependency is injected
> dynamically from another thread).
> We do this because Configuration Admin requires to throw a
> ConfigurationException from the update thread, in case there is a
> configuration error.
> The intent of this issue is simply to stay synchronous (we still throw a
> ConfigurationException from the CM update thread), but instead of calling the
> component "updated" callback from the CM thread, we schedule the update
> callback through the Component internal queue, and we wait for the update
> callback to be executed (using a simple Callbable associated with a
> FutureTask.
> This trick will allow to call the component "updated" callback safely, and
> return any configuration errors to the CM update thread.
> So, basically, instead of doing this in the
> ConfigurationDependencyImpl.updated callback
> {code}
> try {
> invokeUpdated(settings); // either the callback instance or the
> component instances, if available.
> } catch (ConfigurationException e) {
> logConfigurationException(e);
> throw e;
> }
> {code}
> then schedule the update invocation in the component executor and wait for
> the result like this:
> {code}
> Callable<ConfigurationException> result = new
> Callable<ConfigurationException>() {
> @Override
> public ConfigurationException call() throws Exception {
> try {
> invokeUpdated(settings); // either the callback instance
> or the component instances, if available.
> } catch (ConfigurationException e) {
> return e;
> }
> return null;
> }
> };
> FutureTask<ConfigurationException> ft = new FutureTask<>(result);
> m_component.getExecutor().execute(ft);
>
> try {
> ConfigurationException confError = ft.get(UPDATE_MAXWAIT,
> TimeUnit.MILLISECONDS);
> if (confError != null) {
> logConfigurationException(confError);
> throw confError;
> }
> }
> catch (Throwable error) {
> logConfigurationException(error);
> throw new ConfigurationException(null, "Could not handle
> configuration update", error);
> }
> {code}
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