[Background fetching] Background fetching when opening an NTP.

components/ntp_snippets/remote/scheduling_remote_suggestions_provider.cc

 // Copyright 2016 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 "components/ntp_snippets/remote/scheduling_remote_suggestions_provider.h"
 
+#include <random>
 #include <string>
 #include <utility>
 
 #include "base/memory/ptr_util.h"
 #include "components/ntp_snippets/features.h"
 #include "components/ntp_snippets/pref_names.h"
 #include "components/ntp_snippets/remote/persistent_scheduler.h"
 #include "components/ntp_snippets/status.h"
 #include "components/ntp_snippets/user_classifier.h"
 #include "components/prefs/pref_registry_simple.h"
 #include "components/prefs/pref_service.h"
 #include "components/variations/variations_associated_data.h"
 
 namespace ntp_snippets {
 
 namespace {
 
+enum class FetchingInterval {
+  PERSISTENT_FALLBACK,
+  PERSISTENT_WIFI,
+  SOFT_ON_USAGE_EVENT,
+  COUNT
+};
+
 // Default values for fetching intervals, fallback and wifi.
-const double kDefaultFetchingIntervalRareNtpUser[] = {48.0, 24.0};
-const double kDefaultFetchingIntervalActiveNtpUser[] = {24.0, 6.0};
-const double kDefaultFetchingIntervalActiveSuggestionsConsumer[] = {24.0, 6.0};
+const double kDefaultFetchingIntervalRareNtpUser[] = {48.0, 24.0, 12.0};
+const double kDefaultFetchingIntervalActiveNtpUser[] = {24.0, 6.0, 2.0};
+const double kDefaultFetchingIntervalActiveSuggestionsConsumer[] = {24.0, 6.0,
+                                                                    2.0};
 
 // Variation parameters than can the default fetching intervals.
 const char* kFetchingIntervalParamNameRareNtpUser[] = {
     "fetching_interval_hours-fallback-rare_ntp_user",
-    "fetching_interval_hours-wifi-rare_ntp_user"};
+    "fetching_interval_hours-wifi-rare_ntp_user",
+    "soft_fetching_interval_hours-active-rare_ntp_user"};
 const char* kFetchingIntervalParamNameActiveNtpUser[] = {
     "fetching_interval_hours-fallback-active_ntp_user",
-    "fetching_interval_hours-wifi-active_ntp_user"};
+    "fetching_interval_hours-wifi-active_ntp_user",
+    "soft_fetching_interval_hours-active-active_ntp_user"};
 const char* kFetchingIntervalParamNameActiveSuggestionsConsumer[] = {
     "fetching_interval_hours-fallback-active_suggestions_consumer",
-    "fetching_interval_hours-wifi-active_suggestions_consumer"};
+    "fetching_interval_hours-wifi-active_suggestions_consumer",
+    "soft_fetching_interval_hours-active-active_suggestions_consumer"};
 
-base::TimeDelta GetDesiredUpdateInterval(
-    bool is_wifi,
+static_assert(
+    static_cast<unsigned int>(FetchingInterval::COUNT) ==
+            arraysize(kDefaultFetchingIntervalRareNtpUser) &&
+        static_cast<unsigned int>(FetchingInterval::COUNT) ==
+            arraysize(kDefaultFetchingIntervalActiveNtpUser) &&
+        static_cast<unsigned int>(FetchingInterval::COUNT) ==
+            arraysize(kDefaultFetchingIntervalActiveSuggestionsConsumer) &&
+        static_cast<unsigned int>(FetchingInterval::COUNT) ==
+            arraysize(kFetchingIntervalParamNameRareNtpUser) &&
+        static_cast<unsigned int>(FetchingInterval::COUNT) ==
+            arraysize(kFetchingIntervalParamNameActiveNtpUser) &&
+        static_cast<unsigned int>(FetchingInterval::COUNT) ==
+            arraysize(kFetchingIntervalParamNameActiveSuggestionsConsumer),
+    "Fill in all the info for fetching intervals.");
+
+base::TimeDelta GetDesiredFetchingInterval(
+    FetchingInterval interval,
     UserClassifier::UserClass user_class) {
   double default_value_hours = 0.0;
 
-  const int index = is_wifi ? 1 : 0;
+  DCHECK(interval != FetchingInterval::COUNT);
+  const unsigned int index = static_cast<unsigned int>(interval);
+  DCHECK(index < arraysize(kDefaultFetchingIntervalRareNtpUser));
+
   const char* param_name = nullptr;
   switch (user_class) {
     case UserClassifier::UserClass::RARE_NTP_USER:
       default_value_hours = kDefaultFetchingIntervalRareNtpUser[index];
       param_name = kFetchingIntervalParamNameRareNtpUser[index];
       break;
     case UserClassifier::UserClass::ACTIVE_NTP_USER:
       default_value_hours = kDefaultFetchingIntervalActiveNtpUser[index];
       param_name = kFetchingIntervalParamNameActiveNtpUser[index];
       break;
     case UserClassifier::UserClass::ACTIVE_SUGGESTIONS_CONSUMER:
       default_value_hours =
           kDefaultFetchingIntervalActiveSuggestionsConsumer[index];
       param_name = kFetchingIntervalParamNameActiveSuggestionsConsumer[index];
       break;
   }
 
   double value_hours = variations::GetVariationParamByFeatureAsDouble(
       ntp_snippets::kArticleSuggestionsFeature, param_name,
       default_value_hours);
 
   return base::TimeDelta::FromSecondsD(value_hours * 3600.0);
 }
 
 }  // namespace
 
 struct SchedulingRemoteSuggestionsProvider::FetchingSchedule {
-  base::TimeDelta interval_wifi;
-  base::TimeDelta interval_fallback;
+  base::TimeDelta interval_persistent_wifi;
+  base::TimeDelta interval_persistent_fallback;
+  base::TimeDelta interval_soft_on_usage_event;
 
   static FetchingSchedule Empty() {
-    return FetchingSchedule{base::TimeDelta(),
+    return FetchingSchedule{base::TimeDelta(), base::TimeDelta(),
                             base::TimeDelta()};
   }
 
   bool operator==(const FetchingSchedule& other) const {
-    return interval_wifi == other.interval_wifi &&
-           interval_fallback == other.interval_fallback;
+    return interval_persistent_wifi == other.interval_persistent_wifi &&
+           interval_persistent_fallback == other.interval_persistent_fallback &&
+           interval_soft_on_usage_event == other.interval_soft_on_usage_event;
   }
 
   bool operator!=(const FetchingSchedule& other) const {
     return !operator==(other);
   }
 
   bool is_empty() const {
-    return interval_wifi.is_zero() && interval_fallback.is_zero();
+    return interval_persistent_wifi.is_zero() &&
+           interval_persistent_fallback.is_zero() &&
+           interval_soft_on_usage_event.is_zero();
   }
 };
 
 SchedulingRemoteSuggestionsProvider::SchedulingRemoteSuggestionsProvider(
     Observer* observer,
     std::unique_ptr<RemoteSuggestionsProvider> provider,
     PersistentScheduler* persistent_scheduler,
     const UserClassifier* user_classifier,
     PrefService* pref_service)
     : RemoteSuggestionsProvider(observer),
@@ skipping 11 matching lines @@
               &SchedulingRemoteSuggestionsProvider::OnProviderStatusChanged,
               base::Unretained(this))));
 }
 
 SchedulingRemoteSuggestionsProvider::~SchedulingRemoteSuggestionsProvider() =
     default;
 
 // static
 void SchedulingRemoteSuggestionsProvider::RegisterProfilePrefs(
     PrefRegistrySimple* registry) {
-  registry->RegisterInt64Pref(prefs::kSnippetBackgroundFetchingIntervalWifi, 0);
-  registry->RegisterInt64Pref(prefs::kSnippetBackgroundFetchingIntervalFallback,
+  registry->RegisterInt64Pref(prefs::kSnippetPersistentFetchingIntervalWifi, 0);
+  registry->RegisterInt64Pref(prefs::kSnippetPersistentFetchingIntervalFallback,
                               0);
+  registry->RegisterInt64Pref(prefs::kSnippetSoftFetchingIntervalOnUsageEvent,
+                              0);
+  registry->RegisterInt64Pref(prefs::kSnippetLastBackgroundFetchAttempt, 0);
 }
 
 void SchedulingRemoteSuggestionsProvider::RescheduleFetching() {
   // Force the reschedule by stopping and starting it again.
   StopScheduling();
   StartScheduling();
 }
 
 void SchedulingRemoteSuggestionsProvider::OnPersistentSchedulerWakeUp() {
-  provider_->RefetchInTheBackground(
-      base::MakeUnique<RemoteSuggestionsProvider::FetchStatusCallback>(
-          base::Bind(&SchedulingRemoteSuggestionsProvider::OnFetchCompleted,
-                     base::Unretained(this))));
+  RefetchInTheBackground(/*callback=*/nullptr);
 }
 
 void SchedulingRemoteSuggestionsProvider::OnBrowserStartup() {
   // TODO(jkrcal): Implement.
 }
 
 void SchedulingRemoteSuggestionsProvider::OnNTPOpened() {
-  // TODO(jkrcal): Implement.
+  if (!ShouldRefetchInTheBackgroundNow()) {
+    return;
+  }
+  RefetchInTheBackground(/*callback=*/nullptr);
 }
 
 void SchedulingRemoteSuggestionsProvider::SetProviderStatusCallback(
-      std::unique_ptr<ProviderStatusCallback> callback) {
+    std::unique_ptr<ProviderStatusCallback> callback) {
   provider_->SetProviderStatusCallback(std::move(callback));
 }
 
 void SchedulingRemoteSuggestionsProvider::RefetchInTheBackground(
     std::unique_ptr<FetchStatusCallback> callback) {
-  provider_->RefetchInTheBackground(std::move(callback));
+  if (background_fetch_in_progress_) {
+    if (callback) {
+      callback->Run(
+          Status(StatusCode::TEMPORARY_ERROR, "Background fetch in progress"));
+    }
+    return;
+  }
+
+  RemoteSuggestionsProvider::FetchStatusCallback wrapper_callback = base::Bind(
+      &SchedulingRemoteSuggestionsProvider::RefetchInTheBackgroundFinished,
+      base::Unretained(this), base::Passed(&callback));
+  provider_->RefetchInTheBackground(
+      base::MakeUnique<RemoteSuggestionsProvider::FetchStatusCallback>(
+          std::move(wrapper_callback)));
 }
 
 const NTPSnippetsFetcher* SchedulingRemoteSuggestionsProvider::
     snippets_fetcher_for_testing_and_debugging() const {
   return provider_->snippets_fetcher_for_testing_and_debugging();
 }
 
 CategoryStatus SchedulingRemoteSuggestionsProvider::GetCategoryStatus(
     Category category) {
   return provider_->GetCategoryStatus(category);
@@ skipping 63 matching lines @@
       StartScheduling();
       return;
     case RemoteSuggestionsProvider::ProviderStatus::INACTIVE:
       StopScheduling();
       return;
   }
   NOTREACHED();
 }
 
 void SchedulingRemoteSuggestionsProvider::StartScheduling() {
-  // The scheduler only exists on Android so far, it's null on other platforms.
-  if (!persistent_scheduler_) {
-    return;
-  }
-
   FetchingSchedule last_schedule = GetLastFetchingSchedule();
   FetchingSchedule schedule = GetDesiredFetchingSchedule();
 
   // Reset the schedule only if the parameters have changed.
   if (last_schedule != schedule) {
-    ApplyFetchingSchedule(schedule);
+    ApplyFetchingSchedule(schedule, /*also_apply_persistent_schedule=*/true);
   }
 }
 
 void SchedulingRemoteSuggestionsProvider::StopScheduling() {
-  // The scheduler only exists on Android so far, it's null on other platforms.
-  if (!persistent_scheduler_) {
-    return;
-  }
-
   // Do not unschedule if already switched off
   FetchingSchedule last_schedule = GetLastFetchingSchedule();
   if (last_schedule.is_empty()) {
     return;
   }
 
-  persistent_scheduler_->Unschedule();
+  pref_service_->ClearPref(prefs::kSnippetLastBackgroundFetchAttempt);
+
+  // The scheduler only exists on Android so far, it's null on other platforms.
+  if (persistent_scheduler_) {
+    persistent_scheduler_->Unschedule();
+  }
 
   StoreLastFetchingSchedule(FetchingSchedule::Empty());
 }
 
 void SchedulingRemoteSuggestionsProvider::ApplyFetchingSchedule(
-    const FetchingSchedule& schedule) {
-  persistent_scheduler_->Schedule(schedule.interval_wifi,
-                                  schedule.interval_fallback);
+    const FetchingSchedule& schedule,
+    bool also_apply_persistent_schedule) {
+  pref_service_->SetInt64(prefs::kSnippetLastBackgroundFetchAttempt,

[tschumann, 2017/01/03 18:54:25]

from an offline discussion: We also call this on StartScheduling() which
essentially messes up the information of the actual last fetch.
I'm fine with getting this addressed in a follow-up CL where we can also clean
up the 'is-activated' logic in ShouldRefetchInTheBackgroundNow() -- we shouldn't
abuse the last scheduled time-stamp for that.

[jkrcal, 2017/01/04 10:06:30]

Fixed, in the end.

+                          base::Time::Now().ToInternalValue());
+
+  // The scheduler only exists on Android so far, it's null on other platforms.
+  if (persistent_scheduler_ && also_apply_persistent_schedule) {
+    persistent_scheduler_->Schedule(schedule.interval_persistent_wifi,
+                                    schedule.interval_persistent_fallback);
+  }
 
   StoreLastFetchingSchedule(schedule);
 }
 
 SchedulingRemoteSuggestionsProvider::FetchingSchedule
 SchedulingRemoteSuggestionsProvider::GetDesiredFetchingSchedule() const {
   UserClassifier::UserClass user_class = user_classifier_->GetUserClass();
 
   FetchingSchedule schedule;
-  schedule.interval_wifi =
-      GetDesiredUpdateInterval(/*is_wifi=*/true, user_class);
-  schedule.interval_fallback =
-      GetDesiredUpdateInterval(/*is_wifi=*/false, user_class);
+  schedule.interval_persistent_wifi =
+      GetDesiredFetchingInterval(FetchingInterval::PERSISTENT_WIFI, user_class);
+  schedule.interval_persistent_fallback = GetDesiredFetchingInterval(
+      FetchingInterval::PERSISTENT_FALLBACK, user_class);
+  schedule.interval_soft_on_usage_event = GetDesiredFetchingInterval(
+      FetchingInterval::SOFT_ON_USAGE_EVENT, user_class);
+
   return schedule;
 }
 
 SchedulingRemoteSuggestionsProvider::FetchingSchedule
 SchedulingRemoteSuggestionsProvider::GetLastFetchingSchedule() const {
   FetchingSchedule schedule;
-  schedule.interval_wifi = base::TimeDelta::FromInternalValue(
-      pref_service_->GetInt64(prefs::kSnippetBackgroundFetchingIntervalWifi));
-  schedule.interval_fallback =
+  schedule.interval_persistent_wifi = base::TimeDelta::FromInternalValue(
+      pref_service_->GetInt64(prefs::kSnippetPersistentFetchingIntervalWifi));
+  schedule.interval_persistent_fallback =
       base::TimeDelta::FromInternalValue(pref_service_->GetInt64(
-          prefs::kSnippetBackgroundFetchingIntervalFallback));
+          prefs::kSnippetPersistentFetchingIntervalFallback));
+  schedule.interval_soft_on_usage_event = base::TimeDelta::FromInternalValue(
+      pref_service_->GetInt64(prefs::kSnippetSoftFetchingIntervalOnUsageEvent));
+
   return schedule;
 }
 
 void SchedulingRemoteSuggestionsProvider::StoreLastFetchingSchedule(
     const FetchingSchedule& schedule) {
+  pref_service_->SetInt64(prefs::kSnippetPersistentFetchingIntervalWifi,
+                          schedule.interval_persistent_wifi.ToInternalValue());
   pref_service_->SetInt64(
-      prefs::kSnippetBackgroundFetchingIntervalWifi,
-      schedule.interval_wifi.ToInternalValue());
+      prefs::kSnippetPersistentFetchingIntervalFallback,
+      schedule.interval_persistent_fallback.ToInternalValue());
   pref_service_->SetInt64(
-      prefs::kSnippetBackgroundFetchingIntervalFallback,
-      schedule.interval_fallback.ToInternalValue());
+      prefs::kSnippetSoftFetchingIntervalOnUsageEvent,
+      schedule.interval_soft_on_usage_event.ToInternalValue());
+}
+
+bool SchedulingRemoteSuggestionsProvider::ShouldRefetchInTheBackgroundNow() {
+  if (!pref_service_->HasPrefPath(prefs::kSnippetLastBackgroundFetchAttempt)) {
+    // Soft background fetches are switched off.
+    return false;
+  }
+
+  FetchingSchedule schedule = GetLastFetchingSchedule();
+
+  base::Time first_allowed_fetch_time =
+      base::Time::FromInternalValue(
+          pref_service_->GetInt64(prefs::kSnippetLastBackgroundFetchAttempt)) +
+      schedule.interval_soft_on_usage_event;
+  return first_allowed_fetch_time <= base::Time::Now();
 }
 
 void SchedulingRemoteSuggestionsProvider::FetchFinished(
     const FetchDoneCallback& callback,
-    Status status_code,
+    Status fetch_status,
     std::vector<ContentSuggestion> suggestions) {
-  OnFetchCompleted(status_code);
-  callback.Run(status_code, std::move(suggestions));
+  // Reschedule after a fetch. The persistent schedule is applied only after a
+  // successful fetch. After a failed fetch, we want to keep the previous
+  // persistent schedule intact so that we eventually get a persistent fallback
+  // fetch (if the wifi persistent fetches keep failing).
+  ApplyFetchingSchedule(GetLastFetchingSchedule(),
+                        /*also_apply_persistent_schedule=*/fetch_status.code ==
+                            StatusCode::SUCCESS);
+
+  callback.Run(fetch_status, std::move(suggestions));
 }
 
-void SchedulingRemoteSuggestionsProvider::OnFetchCompleted(
+void SchedulingRemoteSuggestionsProvider::RefetchInTheBackgroundFinished(
+    std::unique_ptr<FetchStatusCallback> callback,
     Status fetch_status) {
-  // The scheduler only exists on Android so far, it's null on other platforms.
-  if (!persistent_scheduler_) {
-    return;
+  background_fetch_in_progress_ = false;
+
+  // Reschedule after a fetch. The persistent schedule is applied only after a
+  // successful fetch. After a failed fetch, we want to keep the previous
+  // persistent schedule intact so that we eventually get a persistent fallback
+  // fetch (if the wifi persistent fetches keep failing).
+  ApplyFetchingSchedule(GetLastFetchingSchedule(),
+                        /*also_apply_persistent_schedule=*/fetch_status.code ==
+                            StatusCode::SUCCESS);
+
+  if (callback) {
+    callback->Run(fetch_status);
   }
-
-  if (fetch_status.code != StatusCode::SUCCESS) {
-    return;
-  }
-
-  // Reschedule after a successful fetch. This resets all currently scheduled
-  // fetches, to make sure the fallback interval triggers only if no wifi fetch
-  // succeeded, and also that we don't do a background fetch immediately after
-  // a user-initiated one.
-  ApplyFetchingSchedule(GetLastFetchingSchedule());
 }
 
 }  // namespace ntp_snippets