Instead of isTerminated we now use death watch on subscribers.
! Breaking change - ActorClassification based event buses now require
and actor system. Previously no actors were involved, but now someone
has to `watch` the subscribers. The unsubscriber is an system actor,
and won't be stopped automagically if a bus stops to be used (hard to
determine what "stops being used" is)
* Replaced isTerminated checks with watching actors
* backing structure for ActorClassification swaped from
ConcurrentHashMap to immutable.Map with CAS operations on it. This is
required to avoid races and guarantee register/unregister ordering
(messages sent with proper sequence numbers) to the unsubscriber.
Performance tested it and still above 1.3million subscribe+unsubscribe
ops per second (mac i7, retina), where as the CHM version was
4 million - but that one could only work in the presence of
itTerminated - so we pay the price here for removing it.
* `ActorClassification` starts the unsubscriber instance by itself,
the unsubscriber is an system actor, and can be stopped via
`ActorClassification#shutdown`
* Will unregister from unsubscriber, when no more subscriptions for
given subscriber are left in this bus.
* Added missing "Java API: " for some types
* Updated docs to point out the automatic subscriber purging (on terminated)
* because it is not referentially transparent; normally we reserved parens for
side-effecting code but given how people thoughtlessly close over it we revised
that that decision for sender
* caller can still omit parens
* Added LogEvent subclasses with new field for transporting the MDC custom values.
* Slf4jLogger now takes MDC values from new LogEvent field, puts all in MDC before appending the log, and removes all after.
* New trait DiagnosticLoggingAdapter was introduced, which extends LoggingAdapter and adds MDC support with methods to get, set and clear MDC values.
* New factory method added to Logging for getting loggers with MDC support.
* BusLogging was changed to create new LogEvents including the MDC values.
* Actors can mixin with DiagnosticActorLogging which defines a diagnostic logger "log", has a hook to override for defining MDC values per message, and overrides aroundReceive for setting and clearing MDC around receive execution.
* Proper documentation was added for Scala and Java under the Logging/Slf4j section.
The idea is to filter the sources, replacing @<var>@ occurrences with
the mapping for <var> (which is currently hard-coded). @@ -> @. In order
to make this work, I had to move the doc sources one directory down
(into akka-docs/rst) so that the filtered result could be in a sibling
directory so that relative links (to _sphinx plugins or real code) would
continue to work.
While I was at it I also changed it so that WARNINGs and ERRORs are not
swallowed into the debug dump anymore but printed at [warn] level
(minimum).
One piece of fallout is that the (online) html build is now run after
the normal one, not in parallel.
