Small optimization to the external ACL caching behaviour. With bigger than
itself effects.
Admin configure ttl=0 and/or negative_ttl=0 to prevent Squid storing the
ACL lookup results. The problem is that results still get cached and
re-used for the grace= period. IMO this grace period should only occur for
results which are allowed to be re-used.
The attached patch changes the external ACL caching slightly to actually
not store the results when their matching TTL is zero.
Side effects of this (on systems with ttl <= 0 or negative_ttl <= 0) are:
less memory usage
expected non-caching works
FAST category ACL tests not able to be used on non-cached results
less processing cycles on result hash insertion
* traded for potential cycles on hash lookups
Amos
=== modified file 'src/external_acl.cc'
--- src/external_acl.cc 2010-12-14 14:01:14 +0000
+++ src/external_acl.cc 2011-01-24 23:19:34 +0000
@@ -1113,6 +1113,11 @@
static external_acl_entry *
external_acl_cache_add(external_acl * def, const char *key, ExternalACLEntryData const & data)
{
+ // do not bother caching this result if TTL is going to expire it immediately
+ if ((def->ttl <= 0 && data.result == 1) || (def->negative_ttl <= 0 && data.result != 1)) {
+ return NULL;
+ }
+
ExternalACLEntry *entry = static_cast<ExternalACLEntry *>(hash_lookup(def->cache, key));
debugs(82, 2, "external_acl_cache_add: Adding '" << key << "' = " << data.result);
