#+TITLE: 8sync NEWS
-: Copyright (C) 2015 Christopher Allan Webber
+: Copyright (C) 2015-2016 Christopher Allan Webber
:
: Copying and distribution of this file, with or without modification, are
: permitted in any medium without royalty provided the copyright notice
: and this notice are preserved.
+* 8sync 0.4
+** Actors are now "center stage"
+
+You can now import a toplevel (8sync) module, and this module includes
+the full actor model system. The actor model is now *the* way to
+handle concurrent synchronization in 8sync. So, 8sync is officially
+less about its event loop, and more about the actor model. (It is
+even possible that in the future, 8sync's actor model will be able to
+run on another event loop.)
+
+** New 8sync tutorial
+
+The manual as been expanded with a full tutorial, walking from
+extending an existing actor by writing an irc bot, to writing your own
+basic actors, to writing network actors.
+
+** Better error propagation
+
+When actors wait on other procedures, the "wait" handling code happens
+within the actor's message handler, rather than skipping execution
+from the outside. This means it's possible to catch a general purpose
+error named 'hive-unresumable-coroutine within the message handler
+itself.
+
+(The name of the symbol in the thrown exception may change in a future
+release.)
+
+** IRC bot is now an actor
+
+The irc bot code officially has become actor'ified, under the
+<irc-bot> class.
+
+** REPL handling via an actor
+
+The cooperative REPL code now also is handled via an actor. See
+<repl-manager>.
+
+** Major simplifications/cleanup of the agenda
+
+The agenda is significantly less bloated than it was; with actors
+taking center stage, many previous (and somewhat wonkily written)
+chunks of code have been removed or simplified.
+
+** "from" actor is now implicit in sending a message in <-foo procedures
+
+For the various <- style procedures, the actor is now explicitly
+gathered from a parameter managed via the Hive.
+
+** New procedures: <-*, <-reply*
+
+<-* and <-reply* have been added, which like <-wait* and <-reply-wait*
+are like their non-starred equivalents, except they can take some
+additional options.
+
+** New implicit '*init* and '*cleanup* action handlers.
+
+There are now action handlers for '*init* and '*cleanup* which are
+automatically invoked on actor initialization and destruction.
+
+
+* 8sync 0.3
+
+** 8sync now targets Guile 2.2, Guile 2.0 dropped
+
+In order to take advantage of Guile 2.2's suspendable ports facilities,
+Guile 2.0 support has been dropped from 8sync. (The Guile 2.1.X series is
+the Guile 2.2 preview series. A minimum of Guile 2.1.4 is required.)
+
+While this may make 8sync slightly harder to install before major free
+software distributions catch up (Guix users should have no problem), there
+are major benefits to be found as well; networked code will be
+significantly easier to write. For more information, read on.
+
+
+** Suspendable ports overhaul
+
+Previous 8sync networked code required hooking up a "port request" to the
+scheduler, which would assign a port listening on a read or write event
+with a callback. By making use of Guile 2.2's new [[https://www.gnu.org/software/guile/docs/master/guile.html/Non_002dBlocking-I_002fO.html][suspendable ports]] code,
+network enabled code mostly is completely straightforward to write. If a
+port is set to be nonblocking, attempting to read or write to a port that
+would normally block will automatically suspend to 8sync's scheduler. When
+that port is discovered to be ready to read or write, the agenda will
+automatically resume the suspended code. As such, writing nonblocking code
+looks almost exactly like writing blocking code in Guile... very little
+extra work needs to be done.
+
+8sync's internal demos and subsystems have also been updated to this
+feature.
+
+Not all ports will work with the new behavior, but most involving a file
+descriptor will, which is the vast majority of I/O facilities. Hopefully
+over time the range of ports which are available to take advantage of this
+feature will grow.
+
+** Overhaul of the "8sync" and "8sync-*" macros / procedures
+
+The previous 8sync macro was realized to be a flawed design, more or less
+emulating a synchronous call stack while providing the main feature of
+yielding. Thus 8sync, and several related macros (8sync-run-at, 8sync-run,
+8sync-delay, 8sync-run-delay) have been removed, and 8sync-nowait has been
+renamed to 8sync.
+
+This leads to the question, "what is the primary coordination mechanism in
+8sync between asynchronous processes?" At least for now, this is the actor
+subystem. (While 8sync core continues to not require the actor subsystem,
+for the reasons just described, many users will want to use it.)
+
+** Actor system overhaul
+
+Given its increased role in 8sync, the actor system has also received
+several major updates:
+
+*** send-message and friends deprecated in favor of <- and friends
+
+send-message, send-message-wait, reply-message, and reply-message-wait have
+all been removed in favor of what was previously their aliases: <-, <-wait,
+<-reply, and <-reply-wait. The semantics are the same.
+
+*** Message body now "applied" to a procedure
+
+Previously to access a message body's contents, you used message-ref,
+since a message body was merely a key-value property list. There was
+a special purpose message handler to make accessing the contents of a
+message's body easier, with define-mhandler. Now this is no more,
+since invoking a message handler will call the procedure more or less
+like so:
+
+#+BEGIN_SRC scheme
+(apply this-message-handler actor message (message-body this-message))
+#+END_SRC
+
+"Waiting" for a reply message continues to return the message as
+before, but to access its body, the message is likewise applied, using
+either "receive-message" or "call-with-message".
+
+*** New %current-actor parameter
+
+*** Default message handler now "inheritable"
+
+The default message handler now looks at the actor slot of the actor
+and its predecessors, which must have #:allocation #:class or
+#:each-subclass. The #:init-value of the actor slot is just an alist
+of (action-symbol . message-handler). There is convenient sugar for
+defining this alist named "build-actions". Use it!
+
+If for some reason you want to control the way messages are handled
+in some way that is different than the general pattern, you may
+customize the message-handler slot of your actor.
+
+** New yield procedure
+
+Allows asynchronously executing code to voluntarily yield to the scheduler.
+
+** New procedure: 8usleep
+
+Like usleep, but asynchronous.
+
+* 8sync 0.2
+
+The primary update to this release is the inclusion of a new actor
+model subsystem.
+
* 8sync 0.1
This is the first release of 8sync. Welcome to 8sync!
The following features are present already in this very first release:
- An asynchronous event loop
- - Delimited continuation support via the (%8sync) command
+ - Delimited continuation support via the (8sync) command
+ - IRC bot demo
projects / 8sync.git / blobdiff