On Tue, Sep 29, 2009 at 2:35 AM, Stuart Roebuck <stuart.roeb...@gmail.com>wrote:
>
> Apologies if I've missed something obvious but my web search hasn't
> turned anything up...
>
> What are the Scala Actors instability issues? I'm in the process of
> doing some major Scala development work and this comment raises
> concerns that I'd like to understand.
>
The issues (with the Scala Actors in general and Lift's use of them) are:
- Scala Actors use a custom version of Doug Leah's Fork/Join library.
This was necessary for JDK 1.4 support. With JDK 1.5, the
java.util.concurrent stuff should have been used. I was led to understand
that this change was made in Scala 2.7.5, but it was not and even the Scala
2.8 stuff still contains fork-join. The FJ library has a memory retention
issue where it trades memory for non-locking performance and, with many
threads in a thread-pool, this leads to out of memory issues.
- The Scala Actor code is very brittle. See
http://erikengbrecht.blogspot.com/2009/01/refactoring-scala-actors.html
The code has not been materially refactored, which means that even in
2.8,
there will be significant potential problems with the Actors. Those
potential problems have manifest themselves as real problems in 2.7.x. I
have spent in aggregate nearly 3 weeks of my time since November 2008
working around the defects in the Actor library. It's easier to have our
own Actors (the current Actor library is about 2 days of work on my part and
the refactoring of Lift to work with the existing Actor library is another 2
days of work.)
- EPFL has been generally slow to respond to bug reports. I am very
frustrated and quite frankly tired of having to cajole EPFL into responding
to defects in one of the premier Scala libraries.
I would strongly suggest that you look at Akka. It's got a better view and
implementation of Actors than does the standard Scala distribution. Akka
includes support for distributed actors, etc.
Hope this helps.
>
> Best,
>
> Stuart
>
> On Sep 29, 3:30 am, David Pollak <feeder.of.the.be...@gmail.com>
> wrote:
> > Folks,
> >
> > Given the continued instability of Scala Actors, I've decided to remove
> them
> > from Lift.
> >
> > Specifically, I'm migrating CometActors to sit on top of Lift's Actors.
> > But, you'll also be able to use Akka Actors to power Lift's CometActors.
> > Specifically, I'm working with Jonas to make sure that we share a common
> > interface to Actors.
> >
> > I've gotten Lift nearly completely migrated over to Lift's Actors on the
> > dpp_wip_actorize branch. Seehttp://
> github.com/dpp/liftweb/tree/dpp_wip_actorize
> >
> > There will be some breaking changes to your applications. Specifically:
> >
> > - Box will be moved to a new package, net.liftweb.base (this is where
> the
> > interface for Actors will live as well)
> > - If you make any assumptions about your CometActors being Scala
> Actors
> > (e.g., using linking), you will have to rewrite this code
> > - Some methods in Lift that currently take Scala Actors as parameters
> > will take Lift Actors (e.g., ActorPing)
> >
> > There will be a parallel Maven repository with the new Lift Actor stuff
> in
> > it so you will be able to build you apps against the new code before the
> > official switch-over.
> >
> > Milestone 6 (which should be out next week) will be based on the existing
> > Actor model. After we get feedback from the community about the new
> Actor
> > stuff, we will switch -SNAPSHOT over to the new Actor stuff.
> >
> > Questions, thoughts, or comments?
> >
> > Thanks,
> >
> > David
> >
> > --
> > Lift, the simply functional web frameworkhttp://liftweb.net
> > Beginning Scalahttp://www.apress.com/book/view/1430219890
> > Follow me:http://twitter.com/dpp
> > Surf the harmonics
>
> >
>
--
Lift, the simply functional web framework http://liftweb.net
Beginning Scala http://www.apress.com/book/view/1430219890
Follow me: http://twitter.com/dpp
Surf the harmonics
--~--~---------~--~----~------------~-------~--~----~
You received this message because you are subscribed to the Google Groups
"Lift" group.
To post to this group, send email to liftweb@googlegroups.com
To unsubscribe from this group, send email to
liftweb+unsubscr...@googlegroups.com
For more options, visit this group at
http://groups.google.com/group/liftweb?hl=en
-~----------~----~----~----~------~----~------~--~---
