chrome/browser/predictors/loading_predictor.cc

// Copyright 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 "chrome/browser/predictors/loading_predictor.h"

#include <algorithm>
#include <vector>

#include "base/metrics/histogram_macros.h"
#include "chrome/browser/predictors/loading_data_collector.h"
#include "chrome/browser/predictors/loading_stats_collector.h"
#include "chrome/browser/predictors/navigation_id.h"
#include "chrome/browser/predictors/predictors_features.h"
#include "chrome/browser/predictors/resource_prefetch_predictor.h"
#include "content/public/browser/browser_thread.h"
#include "net/base/network_isolation_key.h"
#include "url/origin.h"

namespace predictors {

namespace {

const base::TimeDelta kMinDelayBetweenPreresolveRequests =
    base::TimeDelta::FromSeconds(60);
const base::TimeDelta kMinDelayBetweenPreconnectRequests =
    base::TimeDelta::FromSeconds(10);

// Returns true iff |prediction| is not empty.
bool AddInitialUrlToPreconnectPrediction(const GURL& initial_url,
                                         PreconnectPrediction* prediction) {
  url::Origin initial_origin = url::Origin::Create(initial_url);
  // Open minimum 2 sockets to the main frame host to speed up the loading if a
  // main page has a redirect to the same host. This is because there can be a
  // race between reading the server redirect response and sending a new request
  // while the connection is still in use.
  static const int kMinSockets = 2;

  if (!prediction->requests.empty() &&
      prediction->requests.front().origin == initial_origin) {
    prediction->requests.front().num_sockets =
        std::max(prediction->requests.front().num_sockets, kMinSockets);
  } else if (!initial_origin.opaque() &&
             (initial_origin.scheme() == url::kHttpScheme ||
              initial_origin.scheme() == url::kHttpsScheme)) {
    prediction->requests.emplace(
        prediction->requests.begin(), initial_origin, kMinSockets,
        net::NetworkIsolationKey(initial_origin, initial_origin));
  }

  return !prediction->requests.empty();
}

}  // namespace

LoadingPredictor::LoadingPredictor(const LoadingPredictorConfig& config,
                                   Profile* profile)
    : config_(config),
      profile_(profile),
      resource_prefetch_predictor_(
          std::make_unique<ResourcePrefetchPredictor>(config, profile)),
      stats_collector_(std::make_unique<LoadingStatsCollector>(
          resource_prefetch_predictor_.get(),
          config)),
      loading_data_collector_(std::make_unique<LoadingDataCollector>(
          resource_prefetch_predictor_.get(),
          stats_collector_.get(),
          config)) {}

LoadingPredictor::~LoadingPredictor() {
  DCHECK(shutdown_);
}

bool LoadingPredictor::PrepareForPageLoad(
    const GURL& url,
    HintOrigin origin,
    bool preconnectable,
    base::Optional<PreconnectPrediction> preconnect_prediction) {
  if (shutdown_)
    return true;

  if (origin == HintOrigin::OMNIBOX) {
    // Omnibox hints are lightweight and need a special treatment.
    HandleOmniboxHint(url, preconnectable);
    return true;
  }

  PreconnectPrediction prediction;
  bool has_local_preconnect_prediction = false;
  if (features::ShouldUseLocalPredictions()) {
    has_local_preconnect_prediction =
        resource_prefetch_predictor_->PredictPreconnectOrigins(url,
                                                               &prediction);
  }
  if (active_hints_.find(url) != active_hints_.end() &&
      has_local_preconnect_prediction && !preconnect_prediction) {
    // We are currently preconnecting using the local preconnect prediction. Do
    // not proceed further.
    return true;
  }

  if (preconnect_prediction) {
    // Overwrite the prediction if we were provided with a non-empty one.
    prediction = *preconnect_prediction;
  } else {
    // Try to preconnect to the |url| even if the predictor has no
    // prediction.
    AddInitialUrlToPreconnectPrediction(url, &prediction);
  }

  // Return early if we do not have any requests.
  if (prediction.requests.empty() && prediction.prefetch_requests.empty())
    return false;

  ++total_hints_activated_;
  active_hints_.emplace(url, base::TimeTicks::Now());
  if (IsPreconnectAllowed(profile_))
    MaybeAddPreconnect(url, std::move(prediction), origin);
  return has_local_preconnect_prediction || preconnect_prediction;
}

void LoadingPredictor::CancelPageLoadHint(const GURL& url) {
  if (shutdown_)
    return;

  CancelActiveHint(active_hints_.find(url));
}

void LoadingPredictor::StartInitialization() {
  if (shutdown_)
    return;

  resource_prefetch_predictor_->StartInitialization();
}

LoadingDataCollector* LoadingPredictor::loading_data_collector() {
  return loading_data_collector_.get();
}

ResourcePrefetchPredictor* LoadingPredictor::resource_prefetch_predictor() {
  return resource_prefetch_predictor_.get();
}

PreconnectManager* LoadingPredictor::preconnect_manager() {
  if (shutdown_ || !IsPreconnectFeatureEnabled())
    return nullptr;

  if (!preconnect_manager_) {
    preconnect_manager_ =
        std::make_unique<PreconnectManager>(GetWeakPtr(), profile_);
  }

  return preconnect_manager_.get();
}

PrefetchManager* LoadingPredictor::prefetch_manager() {
  if (!base::FeatureList::IsEnabled(features::kLoadingPredictorPrefetch))
    return nullptr;

  if (shutdown_ || !IsPreconnectFeatureEnabled())
    return nullptr;

  if (!prefetch_manager_) {
    prefetch_manager_ =
        std::make_unique<PrefetchManager>(GetWeakPtr(), profile_);
  }

  return prefetch_manager_.get();
}

void LoadingPredictor::Shutdown() {
  DCHECK(!shutdown_);
  resource_prefetch_predictor_->Shutdown();
  shutdown_ = true;
}

bool LoadingPredictor::OnNavigationStarted(const NavigationID& navigation_id) {
  if (shutdown_)
    return true;

  loading_data_collector()->RecordStartNavigation(navigation_id);
  CleanupAbandonedHintsAndNavigations(navigation_id);
  active_navigations_.emplace(navigation_id);
  active_urls_to_navigations_[navigation_id.main_frame_url].insert(
      navigation_id);
  return PrepareForPageLoad(navigation_id.main_frame_url,
                            HintOrigin::NAVIGATION);
}

void LoadingPredictor::OnNavigationFinished(
    const NavigationID& old_navigation_id,
    const NavigationID& new_navigation_id,
    bool is_error_page) {
  if (shutdown_)
    return;

  loading_data_collector()->RecordFinishNavigation(
      old_navigation_id, new_navigation_id, is_error_page);
  if (active_urls_to_navigations_.find(old_navigation_id.main_frame_url) !=
      active_urls_to_navigations_.end()) {
    active_urls_to_navigations_[old_navigation_id.main_frame_url].erase(
        old_navigation_id);
    if (active_urls_to_navigations_[old_navigation_id.main_frame_url].empty()) {
      active_urls_to_navigations_.erase(old_navigation_id.main_frame_url);
    }
  }
  active_navigations_.erase(old_navigation_id);
  CancelPageLoadHint(old_navigation_id.main_frame_url);
}

std::map<GURL, base::TimeTicks>::iterator LoadingPredictor::CancelActiveHint(
    std::map<GURL, base::TimeTicks>::iterator hint_it) {
  if (hint_it == active_hints_.end())
    return hint_it;

  const GURL& url = hint_it->first;
  MaybeRemovePreconnect(url);
  return active_hints_.erase(hint_it);
}

void LoadingPredictor::CleanupAbandonedHintsAndNavigations(
    const NavigationID& navigation_id) {
  base::TimeTicks time_now = base::TimeTicks::Now();
  const base::TimeDelta max_navigation_age =
      base::TimeDelta::FromSeconds(config_.max_navigation_lifetime_seconds);

  // Hints.
  for (auto it = active_hints_.begin(); it != active_hints_.end();) {
    base::TimeDelta prefetch_age = time_now - it->second;
    if (prefetch_age > max_navigation_age) {
      // Will go to the last bucket in the duration reported in
      // CancelActiveHint() meaning that the duration was unlimited.
      it = CancelActiveHint(it);
    } else {
      ++it;
    }
  }

  // Navigations.
  for (auto it = active_navigations_.begin();
       it != active_navigations_.end();) {
    if ((it->tab_id == navigation_id.tab_id) ||
        (time_now - it->creation_time > max_navigation_age)) {
      CancelActiveHint(active_hints_.find(it->main_frame_url));
      it = active_navigations_.erase(it);
    } else {
      ++it;
    }
  }
}

void LoadingPredictor::MaybeAddPreconnect(const GURL& url,
                                          PreconnectPrediction prediction,
                                          HintOrigin origin) {
  DCHECK(!shutdown_);
  if (!prediction.prefetch_requests.empty()) {
    DCHECK(base::FeatureList::IsEnabled(features::kLoadingPredictorPrefetch));
    prefetch_manager()->Start(url, std::move(prediction.prefetch_requests));
  }
  if (!prediction.requests.empty())
    preconnect_manager()->Start(url, std::move(prediction.requests));
}

void LoadingPredictor::MaybeRemovePreconnect(const GURL& url) {
  DCHECK(!shutdown_);
  if (preconnect_manager_)
    preconnect_manager_->Stop(url);
  if (prefetch_manager_)
    prefetch_manager_->Stop(url);
}

void LoadingPredictor::HandleOmniboxHint(const GURL& url, bool preconnectable) {
  if (!url.is_valid() || !url.has_host() || !IsPreconnectAllowed(profile_))
    return;

  url::Origin origin = url::Origin::Create(url);
  bool is_new_origin = origin != last_omnibox_origin_;
  last_omnibox_origin_ = origin;
  net::NetworkIsolationKey network_isolation_key(origin, origin);
  base::TimeTicks now = base::TimeTicks::Now();
  if (preconnectable) {
    if (is_new_origin || now - last_omnibox_preconnect_time_ >=
                             kMinDelayBetweenPreconnectRequests) {
      last_omnibox_preconnect_time_ = now;
      preconnect_manager()->StartPreconnectUrl(url, true,
                                               network_isolation_key);
    }
    return;
  }

  if (is_new_origin || now - last_omnibox_preresolve_time_ >=
                           kMinDelayBetweenPreresolveRequests) {
    last_omnibox_preresolve_time_ = now;
    preconnect_manager()->StartPreresolveHost(url, network_isolation_key);
  }
}

void LoadingPredictor::PreconnectInitiated(const GURL& url,
                                           const GURL& preconnect_url) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (shutdown_)
    return;

  auto nav_id_set_it = active_urls_to_navigations_.find(url);
  if (nav_id_set_it == active_urls_to_navigations_.end())
    return;

  for (const auto& nav_id : nav_id_set_it->second)
    loading_data_collector_->RecordPreconnectInitiated(nav_id, preconnect_url);
}

void LoadingPredictor::PreconnectFinished(
    std::unique_ptr<PreconnectStats> stats) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (shutdown_)
    return;

  DCHECK(stats);
  active_hints_.erase(stats->url);
  stats_collector_->RecordPreconnectStats(std::move(stats));
}

void LoadingPredictor::PrefetchInitiated(const GURL& url,
                                         const GURL& prefetch_url) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (shutdown_)
    return;

  auto nav_id_set_it = active_urls_to_navigations_.find(url);
  if (nav_id_set_it == active_urls_to_navigations_.end())
    return;

  for (const auto& nav_id : nav_id_set_it->second)
    loading_data_collector_->RecordPrefetchInitiated(nav_id, prefetch_url);
}

void LoadingPredictor::PrefetchFinished(std::unique_ptr<PrefetchStats> stats) {
  DCHECK_CURRENTLY_ON(content::BrowserThread::UI);
  if (shutdown_)
    return;

  active_hints_.erase(stats->url);
}

void LoadingPredictor::PreconnectURLIfAllowed(
    const GURL& url,
    bool allow_credentials,
    const net::NetworkIsolationKey& network_isolation_key) {
  if (!url.is_valid() || !url.has_host() || !IsPreconnectAllowed(profile_))
    return;
  preconnect_manager()->StartPreconnectUrl(url, allow_credentials,
                                           network_isolation_key);
}

}  // namespace predictors