[trafficserver] 01/02: Stop looping refreshing stale hostDB records

[bc...@apache.org]

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bcall pushed a commit to branch master
in repository https://gitbox.apache.org/repos/asf/trafficserver.git

commit beac65843e6e80a3c7859aceee121920042da867
Author: Zizhong Zhang <zi...@linkedin.com>
AuthorDate: Sat May 27 00:01:21 2017 -0700

    Stop looping refreshing stale hostDB records
---
 iocore/hostdb/HostDB.cc           | 17 +++++++++++++++++
 iocore/hostdb/P_HostDBProcessor.h |  5 +++--
 2 files changed, 20 insertions(+), 2 deletions(-)

diff --git a/iocore/hostdb/HostDB.cc b/iocore/hostdb/HostDB.cc
index 57295bb..c0afd34 100644
--- a/iocore/hostdb/HostDB.cc
+++ b/iocore/hostdb/HostDB.cc
@@ -239,6 +239,18 @@ HostDBCache::HostDBCache() : refcountcache(nullptr), pending_dns(nullptr), remot
   hosts_file_ptr = new RefCountedHostsFileMap();
 }
 
+bool
+HostDBCache::is_pending_dns_for_hash(const INK_MD5 &md5_hash)
+{
+  Queue<HostDBContinuation> &q = pending_dns_for_hash(md5_hash);
+  for (HostDBContinuation *c = q.head; c; c = (HostDBContinuation *)c->link.next) {
+    if (md5_hash == c->md5.hash) {
+      return true;
+    }
+  }
+  return false;
+}
+
 HostDBCache *
 HostDBProcessor::cache()
 {
@@ -554,6 +566,11 @@ probe(ProxyMutex *mutex, HostDBMD5 const &md5, bool ignore_timeout)
 
   // If the record is stale, but we want to revalidate-- lets start that up
   if ((!ignore_timeout && r->is_ip_stale() && !r->reverse_dns) || (r->is_ip_timeout() && r->serve_stale_but_revalidate())) {
+    if (hostDB.is_pending_dns_for_hash(md5.hash)) {
+      Debug("hostdb", "stale %u %u %u, using it and pending to refresh it", r->ip_interval(), r->ip_timestamp,
+            r->ip_timeout_interval);
+      return r;
+    }
     Debug("hostdb", "stale %u %u %u, using it and refreshing it", r->ip_interval(), r->ip_timestamp, r->ip_timeout_interval);
     HostDBContinuation *c = hostDBContAllocator.alloc();
     HostDBContinuation::Options copt;
diff --git a/iocore/hostdb/P_HostDBProcessor.h b/iocore/hostdb/P_HostDBProcessor.h
index 46432be..d1f257d 100644
--- a/iocore/hostdb/P_HostDBProcessor.h
+++ b/iocore/hostdb/P_HostDBProcessor.h
@@ -198,9 +198,10 @@ struct HostDBCache {
 
   // TODO configurable number of items in the cache
   Queue<HostDBContinuation, Continuation::Link_link> *pending_dns;
-  Queue<HostDBContinuation, Continuation::Link_link> &pending_dns_for_hash(INK_MD5 &md5);
+  Queue<HostDBContinuation, Continuation::Link_link> &pending_dns_for_hash(const INK_MD5 &md5);
   Queue<HostDBContinuation, Continuation::Link_link> *remoteHostDBQueue;
   HostDBCache();
+  bool is_pending_dns_for_hash(const INK_MD5 &md5);
 };
 
 inline int
@@ -519,7 +520,7 @@ is_dotted_form_hostname(const char *c)
 }
 
 inline Queue<HostDBContinuation> &
-HostDBCache::pending_dns_for_hash(INK_MD5 &md5)
+HostDBCache::pending_dns_for_hash(const INK_MD5 &md5)
 {
   return pending_dns[this->refcountcache->partition_for_key(md5.fold())];
 }

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