On Tuesday, 9 September 2014 at 22:34:09 UTC, Sean Kelly wrote:
On Monday, 8 September 2014 at 17:24:53 UTC, Marc Schütz wrote:
AFAICS, the documentation doesn't write about any ordering
guarantees of messages, but I can imagine that there are
implicit expectations. In particular prioritySend() could
break, if the implementation isn't done carefully.
The actor model imposes no requirement on the order of received
messages. However, I want to try and guarantee that messages
will be received from a given sender in the order that they were
sent. I think this is a much easier model to code to, and it's
what people expect.
This example from Andrei's TDPL certainly depends on it:
http://www.informit.com/articles/article.aspx?p=1609144&seqNum=7
It would be much more difficult to implement without an ordering
guarantee.
It may be that at some point in the future
for some desirable communication protocol it will not be
possible
to make this guarantee, but in that case the people who choose
to
use that protocol can make an informed decision concerning the
tradeoffs.
UDP comes to mind; it is neither reliable nor guarantees ordering.
I think there should be an explicit guarantee for those protocols
that can provide it. Otherwise it would just be an implementation
detail that cannot be relied upon, and people always have to
assume the worst.
