I have been using varnish for a particular web blog/forum app, so far
it is working well, except that forum users get confused when they
delete or add a post and do not see the changed page immediately; so
they either double-click (meaning a duplicate post) or try to delete
something that has already been deleted.
In any case, the first rule is "don't confuse the user", so since I
have trained the users to expect one kind of behavior I can't expect
them to automatically adjust to a different behavior.
I ended up commenting out the vcl_fetch routine in the default vcl.conf
and setting default_ttl to 15 seconds on the command line. Basically
this is almost disabling the cache (hits are 10% or so).
Based on my reading, what I think will work best, is to set default_ttl
to a very low value like 5 seconds, then use a regexp to specify
explicitly what should be cached.
This works because what I want to cache are the .css, .gif, .jpg, .swf,
.mp3 files - since virtually all the actual HTML is dynamically
generated out of a database, simply off-loading the delivery of other
files is the key thing I want varnish to do.
e.g. "if filename ends in .gif|.jpg|.css|.mp3 add to cache and set
timeout to 600 seconds" ; otherwise default_ttl at 5 seconds will
expire the page and eliminate double-clicks and double-deletes.
Can I put a regexp in the vcl_fetch routine? Just add something like
this to the stock vcl.conf:
sub vcl_fetch {
if (req.url - "/.css|.gif|.jpg|.mp3|.swf/") {
# force minimum ttl of 600 seconds (mod from orig. 180s)
if (obj.ttl < 600s) {
set obj.ttl = 600s;
}
}
}
I am sure I have the syntax wrong, and the regular expression is wrong;
but I think I am clear on what I am trying to do.
Cordially
Patrick Giagnocavo
patrick at zill.net
it is working well, except that forum users get confused when they
delete or add a post and do not see the changed page immediately; so
they either double-click (meaning a duplicate post) or try to delete
something that has already been deleted.
In any case, the first rule is "don't confuse the user", so since I
have trained the users to expect one kind of behavior I can't expect
them to automatically adjust to a different behavior.
I ended up commenting out the vcl_fetch routine in the default vcl.conf
and setting default_ttl to 15 seconds on the command line. Basically
this is almost disabling the cache (hits are 10% or so).
Based on my reading, what I think will work best, is to set default_ttl
to a very low value like 5 seconds, then use a regexp to specify
explicitly what should be cached.
This works because what I want to cache are the .css, .gif, .jpg, .swf,
.mp3 files - since virtually all the actual HTML is dynamically
generated out of a database, simply off-loading the delivery of other
files is the key thing I want varnish to do.
e.g. "if filename ends in .gif|.jpg|.css|.mp3 add to cache and set
timeout to 600 seconds" ; otherwise default_ttl at 5 seconds will
expire the page and eliminate double-clicks and double-deletes.
Can I put a regexp in the vcl_fetch routine? Just add something like
this to the stock vcl.conf:
sub vcl_fetch {
if (req.url - "/.css|.gif|.jpg|.mp3|.swf/") {
# force minimum ttl of 600 seconds (mod from orig. 180s)
if (obj.ttl < 600s) {
set obj.ttl = 600s;
}
}
}
I am sure I have the syntax wrong, and the regular expression is wrong;
but I think I am clear on what I am trying to do.
Cordially
Patrick Giagnocavo
patrick at zill.net