Hi Mathijs, I put that on the list, maybe others have feedback. Summary so far: You see an inconsistency: - methods which have a timeout value usually don't throw on a timeout (like: wait simply returns after timeout) - two exceptions so far: - stream::server.serve (timeout) throws Timeout if no client connected while waiting - close(timeout)/cancel(timeout) calls throw NoSuccess after that time if resources could not be released My opinion: Given that the close/cancel timeouts are less frequently used, those exceptions should probably be changed to TimeOut, to be in sync with stream::server.serve(). I don't think we can get rid off with the exceptions for the three listed calls altogether, at least not without changing semantics. Cheers Andre. Quoting [Mathijs den Burger] (Nov 19 2009):
Subject: Re: Timeout exception in SAGA? From: Mathijs den Burger <mathijs@cs.vu.nl> To: Andre Merzky <andre@merzky.net> Date: Thu, 19 Nov 2009 13:13:41 +0100
On Wed, 2009-11-18 at 21:50 +0100, Andre Merzky wrote:
Quoting [Mathijs den Burger] (Nov 18 2009):
On Tue, 2009-11-17 at 23:36 +0100, Andre Merzky wrote:
Hi Mathijs,
Quoting [Mathijs den Burger] (Nov 17 2009):
Hi Andre,
Page 23 of GFD.90-plus-errata says (in the section on "Freeing of resource and garbage collections"):
"Methods whose semantics depend on successful or unsuccessful de-allo- cation of resources (such as task.cancel() or file.close()) allow for an optional float argument, which defines a timeout for this operation (see Section 2.6.3). If resource de-allocation does not succeed within this timeout period, a NoSuccess exception MUST be thrown."
Shouldn't that be a 'Timeout' exception instead?
The 'Timeout' exception usually implies that communication with a backend is delayed, and that there is a chance that the operation may succeed later on (see description of TimeOut exception). This does also hold for close() and cancel(), which can throw TimeOut in fact, and can be retried. This exception is independent from the timeout parameter though! All calls which *do* have a timeout parameter do *not* throw TimeOut when that time has passed, but simply return (no error).
But the notes of the stream_service.close() call say:
"if no client connects within the specified timeout, a ???Timeout??? exception is thrown."
I'm confused... :)
Me too! ;-) Let me check that stuff again, will answer later...
Do you have time to reply soonish?
Reason: we're current writing an XtreemOS document that includes a SAGA extension package in which we also have an object with a serve() call. I'd like it to mimic stream_service.serve(), but I'm hesistating because it seems inconsistent with the rest of the spec.
The problem is that the description of the Timeout exception does not prescribe what should be the return value of a non-void method when the timeout value is exceeded. The method stream_service.serve() could, for example, return NULL. Still, it seems that throwing a Timeout exception is more logical.
-Mathijs
-- Nothing is ever easy.