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dns_cache: test that zero failure backoff is floored at dns_min_refresh_rate #136

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59 changes: 59 additions & 0 deletions test/extensions/common/dynamic_forward_proxy/dns_cache_impl_test.cc
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Original file line number Diff line number Diff line change
Expand Up @@ -928,6 +928,65 @@ TEST_F(DnsCacheImplTest, ResolveFailureBackoffCappedByHostTtl) {
1 /* added */, 1 /* removed */, 0 /* num hosts */);
}

TEST_F(DnsCacheImplTest, ResolveFailureBackoffZeroFlooredByMinRefresh) {
// Stub random() to return 0 so the jittered exponential backoff yields 0.
ON_CALL(context_.server_context_.api_.random_, random()).WillByDefault(Return(0));
*config_.mutable_host_ttl() = Protobuf::util::TimeUtil::SecondsToDuration(60);
*config_.mutable_dns_refresh_rate() = Protobuf::util::TimeUtil::SecondsToDuration(60);
*config_.mutable_dns_min_refresh_rate() = Protobuf::util::TimeUtil::SecondsToDuration(1);
initialize();
InSequence s;

MockLoadDnsCacheEntryCallbacks callbacks;
Network::DnsResolver::ResolveCb resolve_cb;
Event::MockTimer* resolve_timer = new Event::MockTimer(&context_.server_context_.dispatcher_);
Event::MockTimer* timeout_timer = new Event::MockTimer(&context_.server_context_.dispatcher_);
EXPECT_CALL(*timeout_timer, enableTimer(std::chrono::milliseconds(5000), nullptr));
EXPECT_CALL(*resolver_, resolve("foo.com", _, _))
.WillOnce(DoAll(SaveArg<2>(&resolve_cb), Return(&resolver_->active_query_)));
auto result = dns_cache_->loadDnsCacheEntry("foo.com", 80, false, callbacks);
EXPECT_EQ(DnsCache::LoadDnsCacheEntryStatus::Loading, result.status_);

EXPECT_CALL(*timeout_timer, disableTimer());
EXPECT_CALL(
update_callbacks_,
onDnsHostAddOrUpdate("foo.com:80", DnsHostInfoEquals("10.0.0.1:80", "foo.com", false)));
EXPECT_CALL(callbacks,
onLoadDnsCacheComplete(DnsHostInfoEquals("10.0.0.1:80", "foo.com", false)));
EXPECT_CALL(update_callbacks_,
onDnsResolutionComplete("foo.com:80",
DnsHostInfoEquals("10.0.0.1:80", "foo.com", false),
Network::DnsResolver::ResolutionStatus::Completed));
EXPECT_CALL(*resolve_timer, enableTimer(std::chrono::milliseconds(dns_ttl_), _));
resolve_cb(Network::DnsResolver::ResolutionStatus::Completed, "",
TestUtility::makeDnsResponse({"10.0.0.1"}));

checkStats(1 /* attempt */, 1 /* success */, 0 /* failure */, 1 /* address changed */,
1 /* added */, 0 /* removed */, 1 /* num hosts */);

// Advance a small amount so elapsed is well below host_ttl.
simTime().advanceTimeWait(std::chrono::milliseconds(100));

EXPECT_CALL(*timeout_timer, enableTimer(std::chrono::milliseconds(5000), nullptr));
EXPECT_CALL(*resolver_, resolve("foo.com", _, _))
.WillOnce(DoAll(SaveArg<2>(&resolve_cb), Return(&resolver_->active_query_)));
resolve_timer->invokeCallback();

// DNS fails. With random()==0 the jittered backoff returns 0. The TTL cap does not kick in
// (host_ttl=60s >> elapsed=100ms). The floor at dns_min_refresh_rate (1s) lifts it to 1000ms.
EXPECT_CALL(*timeout_timer, disableTimer());
EXPECT_CALL(update_callbacks_, onDnsHostAddOrUpdate(_, _)).Times(0);
EXPECT_CALL(callbacks, onLoadDnsCacheComplete(_)).Times(0);
EXPECT_CALL(update_callbacks_,
onDnsResolutionComplete("foo.com:80",
DnsHostInfoEquals("10.0.0.1:80", "foo.com", false),
Network::DnsResolver::ResolutionStatus::Failure));
EXPECT_CALL(*resolve_timer, enableTimer(std::chrono::milliseconds(1000), _));
resolve_cb(Network::DnsResolver::ResolutionStatus::Failure, "", TestUtility::makeDnsResponse({}));
checkStats(2 /* attempt */, 1 /* success */, 1 /* failure */, 1 /* address changed */,
1 /* added */, 0 /* removed */, 1 /* num hosts */);
}

TEST_F(DnsCacheImplTest, DisableRefreshOnFailureContainsFailedHost) {
config_.set_disable_dns_refresh_on_failure(true);

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