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jacksontj pushed a commit to branch master
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The following commit(s) were added to refs/heads/master by this push:
new 131875c TS-4403: Fix stale-while-revalidate on DNS lookup
failures (#609)
131875c is described below
commit 131875cbe7b0975c8c3c4f3d20aa55a5c7caba86
Author: Thomas Jackson <[email protected]>
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
---
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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