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sorber pushed a commit to branch 6.2.x
in repository https://git-dual.apache.org/repos/asf/trafficserver.git
The following commit(s) were added to refs/heads/6.2.x by this push:
new af91bf8 TS-4403: Fix stale-while-revalidate on DNS lookup
failures (#609)
af91bf8 is described below
commit af91bf80d8a6ca1a85056c1ff960f8848b7dfac3
Author: Thomas Jackson <jacksontj...@gmail.com>
AuthorDate: Mon May 2 08:34:05 2016 -0700
TS-4403: Fix stale-while-revalidate on DNS lookup failures (#609)
HostDB's "stale-while-revalidate" feature allows hostdb to return stale
records while doing the DNS lookup in the background. This works properly in
the case where the resolver goes away, but in the case that an error was
returned from the resolver the record in cache was thrown away. This means that
a transient error out in the DNS infrastructure would cause ATS to drop its
stale record it would have contently served-- this patch simply makes hostdb
honor its stale-while-revalidate c [...]
This closes #609
(cherry picked from commit 131875cbe7b0975c8c3c4f3d20aa55a5c7caba86)
---
iocore/hostdb/HostDB.cc | 7 ++++++-
1 file changed, 6 insertions(+), 1 deletion(-)
diff --git a/iocore/hostdb/HostDB.cc b/iocore/hostdb/HostDB.cc
index 8360a9d..b83ddff 100644
--- a/iocore/hostdb/HostDB.cc
+++ b/iocore/hostdb/HostDB.cc
@@ -1501,7 +1501,12 @@ HostDBContinuation::dnsEvent(int event, HostEnt *e)
HostDBInfo *r = NULL;
IpAddr tip; // temp storage if needed.
- if (is_byname()) {
+ // If the DNS lookup failed (errors such as NXDOMAIN, SERVFAIL, etc.) but
we have an old record
+ // which is okay with being served stale-- lets continue to serve the
stale record as long as
+ // the record is willing to be served.
+ if (failed && old_r && old_r->serve_stale_but_revalidate()) {
+ r = old_r;
+ } else if (is_byname()) {
if (first)
ip_addr_set(tip, af, first);
r = lookup_done(tip, md5.host_name, is_rr, ttl_seconds, failed ? 0 :
&e->srv_hosts);
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