I was not 100% precise: it's happening if the services interface extends
"Runnable", rather than just implementing it.
This is ok:
public interface AnyService {
void anything();
}
public class AnyServiceImpl implements AnyService, Runnable {
// ..
}
This will cause the bug:
public interface AnyService extends Runnable {
void anything();
}
Am 27.11.2012 um 17:30 schrieb Christian Riedel:
> Hi everyone,
>
> I wrote about this bug a while ago already, but can't find the original post.
> After lots of debugging I found the reason for a bug in our app. The symptoms
> were that all contributions annotated with @Startup (also the ones from
> Tapestry internal modules) were executed a second time as soon as the app has
> been hit by its first request, i.e. some services got realized.
>
> Now I found the reason and I'm not sure whether it's a real bug in Tapestry
> or if it's a less known side effect of Tapestry's design…
>
> Custom services that implement "Runnable" and have any contributions will
> cause Tapestry to assume all of RegistryStartup's contributions to be
> matching as well, so they'll be executed as soon as that custom service's
> contributions are executed. If you have some execute-one-time-only
> startup-contributions you might get into troubles!
>
> Debug here:
> org.apache.tapestry5.ioc.internal.ModuleImpl#markerMatched(ServiceDef
> serviceDef, Markable markable)
>
> "markable" may be any contribution for RegistryStartup.
> Then "markable.getServiceInterface()" will return the "Runnable" interface,
> which is assignable to your custom service and further down that method the
> contribution that was supposed to be for RegistryStartup will be considered
> as "ContributionDef".
>
> Sure the fixing the bug is easy:
> Just NEVER let any of your services implement Runnable. Why did we do that in
> the first place? Because we wanted to add a job to Tapestry's
> PeriodicExecutor after our custom service got realized, to prevent some
> timing issues. So our services wanted to be a PeriodicExecutor-job.
>
> Another fix for the bug could be to give RegistryStartup its own interface
> and prevent collisions with internal services altogether!
>
> Hope to read some thoughts of committers on that issue.
>
>
> Cheers
> Christian
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