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Posted to dev@felix.apache.org by "Anders Engström (JIRA)" <ji...@apache.org> on 2016/03/20 21:48:33 UTC
[jira] [Commented] (FELIX-5199) Race condition in
HttpServiceFactory.getService() causing exception
[ https://issues.apache.org/jira/browse/FELIX-5199?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=15203515#comment-15203515 ]
Anders Engström commented on FELIX-5199:
----------------------------------------
While investigating FELIX-5219 I ran into some issues that I believe is related to this patch.
If a {{ServiceTracker}} is opened and listening for {{HttpService}} (*before* {{HttpServiceFactory#start}} have been called) the {{active}} flag in {{HttpServiceFactory#getService}} will never be {{!= null}} (and the returned service will be {{null}}.
The reason is that the ServiceTracker will get a callback to {{addingService}} synchronously when the service-factory is registered (line 114 in {{HttpServiceFactory}}. At this point the {{active}} flag is still {{false}} (it's set to {{true}} right after the registration. If the ServiceTracker tries to resolve the service-reference in its {{addingService}} this will call into {{HttpServiceFactory#getService}} - but {{active}} is false, so no service is returned.
I tried setting {{active}} to true just before registering the HttpServiceFactory, and this seemed to work - but perhaps that will lead to similar race conditions as in the original code before this patch?
> Race condition in HttpServiceFactory.getService() causing exception
> -------------------------------------------------------------------
>
> Key: FELIX-5199
> URL: https://issues.apache.org/jira/browse/FELIX-5199
> Project: Felix
> Issue Type: Bug
> Components: HTTP Service
> Affects Versions: http.base-3.0.6
> Reporter: David Bosschaert
> Assignee: David Bosschaert
> Fix For: http.base-3.0.8
>
> Attachments: felix-5199.patch
>
>
> The HttpServiceFactory.getService() is as follows:
> {code}
> public HttpService getService(final Bundle bundle, final ServiceRegistration<HttpService> reg)
> {
> final ServletContext servletContext = this.context;
> if ( servletContext != null ) {
> return new PerBundleHttpServiceImpl(bundle,
> this.sharedHttpService,
> this.context,
> this.contextAttributeListenerManager,
> this.sharedContextAttributes,
> this.requestListenerManager,
> this.requestAttributeListenerManager);
> }
> return null;
> }{code}
> However it is possible that this.context is set to {{null}} after the check for {{null}} is done but before the constructor is called causing a null servlet context to be passed to {{PerBundleHttpServiceImpl}}
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