[Remote suggestions] Report time distribution of triggers

components/ntp_snippets/remote/remote_suggestions_scheduler_impl.cc

Index: components/ntp_snippets/remote/remote_suggestions_scheduler_impl.cc
diff --git a/components/ntp_snippets/remote/remote_suggestions_scheduler_impl.cc b/components/ntp_snippets/remote/remote_suggestions_scheduler_impl.cc
index 699c3b5a246cbceafee6b7c8c5cd0355eb9bd183..3a6cd019a116af65a9c880f0046c55a208ebcfc4 100644
--- a/components/ntp_snippets/remote/remote_suggestions_scheduler_impl.cc
+++ b/components/ntp_snippets/remote/remote_suggestions_scheduler_impl.cc
@@ -145,6 +145,96 @@ base::TimeDelta GetDesiredFetchingInterval(
   return base::TimeDelta::FromSecondsD(value_hours * 3600.0);
 }
 
+void ReportTimeUntilFirstSoftTrigger(UserClassifier::UserClass user_class,
+                                     base::TimeDelta time_until_first_trigger) {
+  switch (user_class) {
+    case UserClassifier::UserClass::RARE_NTP_USER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilFirstSoftTrigger_RareNTPUser",

[Ilya Sherman, 2017/04/12 22:53:42]

Optional: You're welcome to use dot instead of underscore for the suffixes, and
specify separator="." in histograms.xml

[jkrcal, 2017/04/13 08:42:58]

Done.

+          time_until_first_trigger, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);

[Ilya Sherman, 2017/04/12 22:53:42]

Do you need 100 buckets, or would 50 suffice?  50 is the more typical bucket
count, and using extra buckets has a memory usage cost for users.  (Applies to
all of the histograms.)

[jkrcal, 2017/04/13 08:42:58]

Done.

(I did it consistently with a similar histogram
NewTabPage.ContentSuggestions.TimeSinceSuggestionFetched but neither
consistency, nor 100 buckets are actually needed)

+      break;
+    case UserClassifier::UserClass::ACTIVE_NTP_USER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilFirstSoftTrigger_"
+          "ActiveNTPUser",
+          time_until_first_trigger, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+    case UserClassifier::UserClass::ACTIVE_SUGGESTIONS_CONSUMER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilFirstSoftTrigger_"
+          "ActiveSuggestionsConsumer",
+          time_until_first_trigger, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+  }
+}
+
+void ReportTimeUntilSoftFetch(UserClassifier::UserClass user_class,
+                              base::TimeDelta time_until_soft_fetch) {
+  switch (user_class) {
+    case UserClassifier::UserClass::RARE_NTP_USER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilSoftFetch_"
+          "RareNTPUser",
+          time_until_soft_fetch, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+    case UserClassifier::UserClass::ACTIVE_NTP_USER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilSoftFetch_"
+          "ActiveNTPUser",
+          time_until_soft_fetch, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+    case UserClassifier::UserClass::ACTIVE_SUGGESTIONS_CONSUMER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilSoftFetch_"
+          "ActiveSuggestionsConsumer",
+          time_until_soft_fetch, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+  }
+}
+
+void ReportTimeUntilPersistentFetch(
+    UserClassifier::UserClass user_class,
+    base::TimeDelta time_until_persistent_fetch) {
+  switch (user_class) {
+    case UserClassifier::UserClass::RARE_NTP_USER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilPersistentFetch_"
+          "RareNTPUser",
+          time_until_persistent_fetch, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+    case UserClassifier::UserClass::ACTIVE_NTP_USER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilPersistentFetch_"
+          "ActiveNTPUser",
+          time_until_persistent_fetch, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+    case UserClassifier::UserClass::ACTIVE_SUGGESTIONS_CONSUMER:
+      UMA_HISTOGRAM_CUSTOM_TIMES(
+          "NewTabPage.ContentSuggestions.TimeUntilPersistentFetch_"
+          "ActiveSuggestionsConsumer",
+          time_until_persistent_fetch, base::TimeDelta::FromSeconds(1),
+          base::TimeDelta::FromDays(7),
+          /*bucket_count=*/100);
+      break;
+  }
+}
+
 }  // namespace
 
 class EulaState : public web_resource::EulaAcceptedNotifier::Observer {
@@ -246,6 +336,7 @@ RemoteSuggestionsSchedulerImpl::RemoteSuggestionsSchedulerImpl(
           profile_prefs,
           RequestThrottler::RequestType::
               CONTENT_SUGGESTION_FETCHER_ACTIVE_SUGGESTIONS_CONSUMER),
+      time_until_first_trigger_reported_(false),
       eula_state_(base::MakeUnique<EulaState>(local_state_prefs, this)),
       profile_prefs_(profile_prefs),
       clock_(std::move(clock)),
@@ -438,8 +529,17 @@ void RemoteSuggestionsSchedulerImpl::RefetchInTheBackgroundIfAppropriate(
     return;
   }
 
-  if (trigger != TriggerType::PERSISTENT_SCHEDULER_WAKE_UP &&
-      !ShouldRefetchInTheBackgroundNow()) {
+  bool is_soft = trigger != TriggerType::PERSISTENT_SCHEDULER_WAKE_UP;
+  const base::Time last_fetch_attempt_time = base::Time::FromInternalValue(
+      profile_prefs_->GetInt64(prefs::kSnippetLastFetchAttempt));
+
+  if (is_soft && !time_until_first_trigger_reported_) {
+    time_until_first_trigger_reported_ = true;
+    ReportTimeUntilFirstSoftTrigger(user_classifier_->GetUserClass(),
+                                    clock_->Now() - last_fetch_attempt_time);
+  }
+
+  if (is_soft && !ShouldRefetchInTheBackgroundNow(last_fetch_attempt_time)) {
     return;
   }
 
@@ -447,6 +547,14 @@ void RemoteSuggestionsSchedulerImpl::RefetchInTheBackgroundIfAppropriate(
     return;
   }
 
+  if (is_soft) {
+    ReportTimeUntilSoftFetch(user_classifier_->GetUserClass(),
+                             clock_->Now() - last_fetch_attempt_time);
+  } else {
+    ReportTimeUntilPersistentFetch(user_classifier_->GetUserClass(),
+                                   clock_->Now() - last_fetch_attempt_time);
+  }
+
   UMA_HISTOGRAM_ENUMERATION(
       "NewTabPage.ContentSuggestions.BackgroundFetchTrigger",
       static_cast<int>(trigger), static_cast<int>(TriggerType::COUNT));
@@ -457,10 +565,8 @@ void RemoteSuggestionsSchedulerImpl::RefetchInTheBackgroundIfAppropriate(
       base::Unretained(this)));
 }
 
-bool RemoteSuggestionsSchedulerImpl::ShouldRefetchInTheBackgroundNow() {
-  const base::Time last_fetch_attempt_time = base::Time::FromInternalValue(
-      profile_prefs_->GetInt64(prefs::kSnippetLastFetchAttempt));
-
+bool RemoteSuggestionsSchedulerImpl::ShouldRefetchInTheBackgroundNow(
+    base::Time last_fetch_attempt_time) {
   // If we have no persistent scheduler to ask, err on the side of caution.
   bool wifi = false;
   if (persistent_scheduler_) {
@@ -521,6 +627,7 @@ void RemoteSuggestionsSchedulerImpl::RefetchInTheBackgroundFinished(
 void RemoteSuggestionsSchedulerImpl::OnFetchCompleted(Status fetch_status) {
   profile_prefs_->SetInt64(prefs::kSnippetLastFetchAttempt,
                            clock_->Now().ToInternalValue());
+  time_until_first_trigger_reported_ = 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