Document vcl_discard().

git-svn-id: http://www.varnish-cache.org/svn/trunk/varnish-cache@1567 d4fa192b-c00b-0410-8231-f00ffab90ce4

man/vcl.7

@@ -28,7 +28,7 @@
 .\"
 .\" $Id$
 .\"
-.Dd March 28, 2007
+.Dd June 25, 2007
 .Dt VCL 7
 .Os
 .Sh NAME
@@ -285,8 +285,8 @@ Insert the object into the cache, then deliver it to the client.
 .El
 .\" vcl_timeout
 .It Cm vcl_timeout
-Called by the reaper thread when a cached document has reached its
-expiry time.
+Called by the reaper thread shortly before a cached document reaches
+its expiry time.
 .Pp
 The
 .Cm vcl_timeout
@@ -297,6 +297,21 @@ Request a fresh copy of the object from the backend.
 .It Cm discard
 Discard the object.
 .El
+.\" vcl_discard
+.It Cm vcl_discard
+Called by the reaper thread when a cached document is about to be
+discarded, either because it has expired or because space is running
+low.
+.Pp
+The
+.Cm vcl_discard
+subroutine may terminate with one of the following keywords:
+.Bl -tag -width "discard"
+.It Cm discard
+Discard the object.
+.It Cm keep
+Keep the object in cache.
+.El
 .El
 .Pp
 If one of these subroutines is left undefined or terminates without
@@ -408,6 +423,10 @@ sub vcl_fetch {
     insert;
 }
 
+sub vcl_discard {
+    discard;
+}
+
 sub vcl_timeout {
     discard;
 }