Re: [weld-dev] BeanManagerImpl permits multiple Contexts per scope type: why?

On Fri, Nov 2, 2018 at 1:25 AM Martin Kouba <mkouba(a)redhat.com <mailto:mkouba@redhat.com>> wrote: The spec is very clear that this should be possible. See for example 6.5.1. The active context object for a scope: "The container must search for an active instance of Context associated with the scope type." Not so sure about the "very clear" part :-) but yes, you can read it this way and clearly that's the intent so that's good enough for me! Follow-up question: a Context's "activeness" is defined per-thread (section 6.2 <http://docs.jboss.org/cdi/spec/2.0/cdi-spec.html#context>): "At a particular point in the execution of the program a context object may be active with respect to the current thread." So when I ask the BeanManager for the (singular) Context-that-is-active-with-respect-to-the-current-thread by giving it a scope annotation, I get back a Context whose isActive() method returned true at some point during the implementation of the BeanManager#getContext(Class) method <http://docs.jboss.org/cdi/api/2.0/javax/enterprise/inject/spi/BeanManager...;. And certainly I'd hope that once I receive this Context its isActive() method would return true. But this is just a "best effort" area of the specification, right?

Consider a (hypothetical, thought-experiment) stupid Context that tracks whether it's active or not for a given Thread (using a Map of Threads-to-booleans or something similar).  Then pretend solely for discussion purposes that it has a daemon Thread in it that randomly and periodically sets its activeness to true or false for a given Thread. So sometimes a caller of its isActive() method gets true back, and sometimes it gets false based on the random activeness-toggling actions of the internal daemon thread.  Again, this is a thought experiment, not proposed or useful code.  :-) All the BeanManager can do in this (stupid but legal?) case is make a /best effort/: at the time it selects the Context for returning from its getContext(Class) method, the Context must have returned true from its isActive() method (otherwise it would not be a candidate for returning), but the caller of BeanManager#getContext(Class) receiving this stupid Context may invoke isActive() and discover that suddenly it is returning false because of the actions of its stupid embedded daemon thread.  Is this thought-experiment scenario correct and permitted by the laws of the specification? Another way to ask this: is the following statement true or false?  I believe it is true:     There is no requirement that the activeness of a BeanManager-vended Context be immutable with respect to the calling thread.

(It seems this statement must be true or the fact that a Context can throw ContextNotActiveException from its methods would seemingly make no sense.) I'm just trying to understand this area very deeply, particularly with respect to threading.  Thanks as always for your time. Best, Laird