Fix and refactor HttpServerPropertiesImpl's alternative services brokenness expiration behavior

net/http/broken_alternative_services.cc

+// Copyright (c) 2017 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "net/http/broken_alternative_services.h"
+
+#include "base/memory/singleton.h"
+#include "base/time/tick_clock.h"
+#include "base/time/time.h"
+#include "net/http/http_server_properties_impl.h"
+
+namespace net {
+
+namespace {
+
+// Initial delay for broken alternative services.
+const uint64_t kBrokenAlternativeProtocolDelaySecs = 300;
+// Subsequent failures result in exponential (base 2) backoff.
+// Limit binary shift to limit delay to approximately 2 days.
+const int kBrokenDelayMaxShift = 9;
+
+base::TimeDelta ComputeBrokenAlternativeServiceExpirationDelay(
+    int broken_count) {
+  DCHECK(broken_count >= 0);
+  if (broken_count > kBrokenDelayMaxShift)
+    broken_count = kBrokenDelayMaxShift;
+  return base::TimeDelta::FromSeconds(kBrokenAlternativeProtocolDelaySecs) *
+         (1 << broken_count);
+}
+
+}  // namespace
+
+BrokenAlternativeServices::BrokenAlternativeServices(Delegate* delegate,
+                                                     base::TickClock* clock)
+    : delegate_(delegate),
+      clock_(clock),
+      recently_broken_alternative_services_(
+          RecentlyBrokenAlternativeServices::NO_AUTO_EVICT),
+      weak_ptr_factory_(this) {
+  DCHECK(delegate_);
+  DCHECK(clock_);
+}
+
+BrokenAlternativeServices::~BrokenAlternativeServices() {}
+
+void BrokenAlternativeServices::MarkAlternativeServiceBroken(
+    const AlternativeService& alternative_service) {
+  // Empty host means use host of origin, callers are supposed to substitute.
+  DCHECK(!alternative_service.host.empty());
+  DCHECK(alternative_service.protocol != kProtoUnknown);
+
+  auto it = recently_broken_alternative_services_.Get(alternative_service);
+  int broken_count = 0;
+  if (it == recently_broken_alternative_services_.end()) {
+    recently_broken_alternative_services_.Put(alternative_service, 1);
+  } else {
+    broken_count = it->second++;
+  }
+  base::TimeTicks expiration =
+      clock_->NowTicks() +
+      ComputeBrokenAlternativeServiceExpirationDelay(broken_count);
+  // Return if alternative service is already in expiration queue.
+  BrokenAlternativeServiceList::iterator list_it;
+  if (!AddToBrokenAlternativeServiceListAndMap(alternative_service, expiration,
+                                               &list_it)) {
+    return;
+  }
+
+  // If this is now the first entry in the list (i.e. |alternative_service| is
+  // the next alt svc to expire), schedule an expiration task for it.
+  if (list_it == broken_alternative_service_list_.begin()) {
+    ScheduleBrokenAlternateProtocolMappingsExpiration();
+  }
+}
+
+void BrokenAlternativeServices::MarkAlternativeServiceRecentlyBroken(
+    const AlternativeService& alternative_service) {
+  DCHECK(alternative_service.protocol != kProtoUnknown);
+  if (recently_broken_alternative_services_.Get(alternative_service) ==
+      recently_broken_alternative_services_.end()) {
+    recently_broken_alternative_services_.Put(alternative_service, 1);
+  }
+}
+
+bool BrokenAlternativeServices::IsAlternativeServiceBroken(
+    const AlternativeService& alternative_service) const {
+  // Empty host means use host of origin, callers are supposed to substitute.
+  DCHECK(!alternative_service.host.empty());
+  return broken_alternative_service_map_.find(alternative_service) !=
+         broken_alternative_service_map_.end();
+}
+
+bool BrokenAlternativeServices::WasAlternativeServiceRecentlyBroken(
+    const AlternativeService& alternative_service) {
+  return recently_broken_alternative_services_.Get(alternative_service) !=
+         recently_broken_alternative_services_.end();
+}
+
+void BrokenAlternativeServices::ConfirmAlternativeService(
+    const AlternativeService& alternative_service) {
+  if (alternative_service.protocol == kProtoUnknown)
+    return;

[Ryan Hamilton, 2017/05/27 13:28:15]

nit: since we can't mark unknown as broken it doesn't make sense to confirm it.
So how 'bout DCHECK(!unknown)?

[wangyix1, 2017/05/30 21:18:17]

Done.

+
+  // Remove |alternative_service| from |alternative_service_list_| and
+  // |alternative_service_map_|.
+  auto map_it = broken_alternative_service_map_.find(alternative_service);
+  if (map_it != broken_alternative_service_map_.end()) {
+    broken_alternative_service_list_.erase(map_it->second);
+    broken_alternative_service_map_.erase(map_it);
+  }
+
+  auto it = recently_broken_alternative_services_.Get(alternative_service);
+  if (it != recently_broken_alternative_services_.end()) {
+    recently_broken_alternative_services_.Erase(it);
+  }
+}
+
+bool BrokenAlternativeServices::AddToBrokenAlternativeServiceListAndMap(
+    const AlternativeService& alternative_service,
+    base::TimeTicks expiration,
+    BrokenAlternativeServiceList::iterator* it) {
+  DCHECK(it);
+
+  auto map_it = broken_alternative_service_map_.find(alternative_service);
+  if (map_it != broken_alternative_service_map_.end())
+    return false;
+
+  // Iterate from end of |broken_alternative_service_list_| to find where to
+  // insert it to keep the list sorted by expiration time.
+  auto list_it = broken_alternative_service_list_.end();
+  while (list_it != broken_alternative_service_list_.begin()) {
+    --list_it;
+    if (list_it->expiration <= expiration) {
+      ++list_it;
+      break;
+    }
+  }
+
+  // Insert |alternative_service| into the list and the map
+  list_it = broken_alternative_service_list_.insert(
+      list_it, BrokenAltSvcExpireInfo(alternative_service, expiration));
+  broken_alternative_service_map_.insert(
+      std::make_pair(alternative_service, list_it));
+
+  *it = list_it;
+  return true;
+}
+
+void BrokenAlternativeServices::ExpireBrokenAlternateProtocolMappings() {
+  base::TimeTicks now = clock_->NowTicks();
+
+  while (!broken_alternative_service_list_.empty()) {
+    auto it = broken_alternative_service_list_.begin();
+    if (now < it->expiration) {
+      break;
+    }
+
+    delegate_->OnExpireBrokenAlternativeService(it->alternative_service);
+
+    broken_alternative_service_map_.erase(it->alternative_service);
+    broken_alternative_service_list_.erase(it);
+  }
+
+  if (!broken_alternative_service_list_.empty())
+    ScheduleBrokenAlternateProtocolMappingsExpiration();
+}
+
+void BrokenAlternativeServices ::
+    ScheduleBrokenAlternateProtocolMappingsExpiration() {
+  DCHECK(!broken_alternative_service_list_.empty());
+  base::TimeTicks now = clock_->NowTicks();
+  base::TimeTicks when = broken_alternative_service_list_.front().expiration;
+  base::TimeDelta delay = when > now ? when - now : base::TimeDelta();
+  expiration_timer_.Stop();
+  expiration_timer_.Start(
+      FROM_HERE, delay,
+      base::Bind(
+          &BrokenAlternativeServices ::ExpireBrokenAlternateProtocolMappings,
+          weak_ptr_factory_.GetWeakPtr()));
+}
+
+}  // namespace net