On Tue, 20 Jun 2000, Alan Smithee wrote:
> Looking at the new "contents.pg", I noticed that some OLCs have
> expires = [lmt + const(0sec)];
> and some have
> expires = [nmt + const(0sec)];
>
> - What is "nmt"?
> - what does "expires = [lmt + const(0sec)];" mean?
Good questions! Nmt is "next modification time". So "lmt + const(0sec)"
means that object's Expires: header field will contain true expiration
time, i.e., the time matching the next modification time.
Only "now" and "lmt" qualifiers are common in real life. "Nmt" is
something only a benchmark can know/use, in general. PolyMix-3 uses
unrealistic truthful expiration times according to the agreement reached
during the last organizational meeting in Boulder. In short,
participants felt that a performance workload should not expose the fact
that any cache can serve a stale object (and realistic expiration values
would cause stale objects to be served). One can still configure
Polygraph to test that case, of course.
We have updated on-line documentation to explain all supported
qualifiers. Please let me know if the explanation is not detailed
enough:
http://polygraph.ircache.net/doc/pgl/types.html#Pgl:distr
Also, you actually found a bug! The old olcStatic cycle should read
expires = [nmt + const(0sec)];
This is not a big deal, fortunately, because olcStatic is not used in
PolyMix-3, and, for PolyMix-2 tests, one should not use new
distributions anyway. The patch is below.
Thank you,
Alex.
Index: workloads/include/contents.pg
===================================================================
RCS file: /usr/local/CVS/polygraph/workloads/include/contents.pg,v
retrieving revision 1.1.1.1.2.2
diff -u -r1.1.1.1.2.2 contents.pg
--- workloads/include/contents.pg 2000/06/19 04:45:43 1.1.1.1.2.2
+++ workloads/include/contents.pg 2000/06/20 14:26:44
@@ -1,7 +1,5 @@
/*
- * $Id: contents.pg,v 1.1.1.1.2.2 2000/06/19 04:45:43 rousskov Exp $
- *
* Commonly used Content models
*
*/
@@ -15,7 +13,7 @@
length = const(2year); // two year cycle
variance = 0%; // no variance
with_lmt = 100%; // all responses have LMT
- expires = [lmt + const(0sec)]; // everything expires when modified
+ expires = [nmt + const(0sec)]; // everything expires when modified
};
// object life cycle for "HTML" content
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