DependencyManager may miss service registrations
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Key: FELIX-1044
URL: https://issues.apache.org/jira/browse/FELIX-1044
Project: Felix
Issue Type: Bug
Components: Declarative Services (SCR)
Affects Versions: scr-1.0.6
Reporter: Felix Meschberger
Assignee: Felix Meschberger
Fix For: scr-1.0.8
Instances of the DependencyManager class are used to track component references
and to call the bind/unbind methods as appropriate.
There are timing issues, which may cause instances of this class to miss
services.
The serviceAdded method checks whether the component is active before handling
a service registration. Generally this works because the activation of the
component will call the bind() method for all dependency managers. The problem
arises if the service is registered _after_ the DependencyManager has bound
registered services but before the component is fully active (e.g. while the
activate() method is still running): In this case the service is received but
not bound because the component is activating and because the dependency
manager has already been called to bind to registered services, the registering
service is lost.
An approach to explore is to ignore the component state when deciding on
whether to handle the event or not but to add a flag: The flag indicates
whether the DependencyManager.bind method has already been called and hence
future events should be handled. When the DependencyManager.unbind method is
called, the flag should be cleare to prevent event handling. In other words:
* Add boolean flag "open"
* Add open(Object) method to be called during activation. This binds
existing services and sets the "open" flag
* Rename undinb(Object) called during deactivation to close(Object) . This
unbinds all bound services and clears the "open" flag
* Add a check for the "open" flag to the serviceChanged method
* Remove the "handleEvent" method, whose functionality is replaced by the
"open" flag
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