Use Histogram algorithm to calculate DNS timeout.
Honor DnsConfig timeout if it exceeds 5s.
BUG=110197
TEST=net_unittests --gtest_filter=DnsSessionTest.HistogramTimeout*
Review URL: https://chromiumcodereview.appspot.com/20482002
git-svn-id: svn://svn.chromium.org/chrome/trunk/src@214235 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/net/dns/dns_session.cc b/net/dns/dns_session.cc
index 67d5779..ea8b6a1 100644
--- a/net/dns/dns_session.cc
+++ b/net/dns/dns_session.cc
@@ -38,6 +38,8 @@
ServerStats(base::TimeDelta rtt_estimate_param, RttBuckets* buckets)
: last_failure_count(0), rtt_estimate(rtt_estimate_param) {
rtt_histogram.reset(new base::SampleVector(buckets));
+ // Seed histogram with 2 samples at |rtt_estimate| timeout.
+ rtt_histogram->Accumulate(rtt_estimate.InMilliseconds(), 2);
}
// Count of consecutive failures after last success.
@@ -209,18 +211,10 @@
base::TimeDelta DnsSession::NextTimeout(unsigned server_index, int attempt) {
- DCHECK_LT(server_index, server_stats_.size());
-
- base::TimeDelta timeout = config_.timeout;
- // If this server has not responded successfully, then don't wait too long.
- if (server_stats_[server_index]->last_success.is_null())
- return timeout;
-
- // The timeout doubles every full round (each nameserver once).
- unsigned num_backoffs = attempt / config_.nameservers.size();
-
- return std::min(timeout * (1 << num_backoffs),
- base::TimeDelta::FromMilliseconds(kMaxTimeoutMs));
+ // Respect config timeout if it exceeds |kMaxTimeoutMs|.
+ if (config_.timeout.InMilliseconds() >= kMaxTimeoutMs)
+ return config_.timeout;
+ return NextTimeoutFromHistogram(server_index, attempt);
}
// Allocate a socket, already connected to the server address.
