Add a mechanism for collecting Rappor samples on a daily interval.

components/metrics/daily_event.cc

+// Copyright 2014 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/metrics/daily_event.h"
+
+#include "base/i18n/time_formatting.h"
+#include "base/metrics/histogram.h"
+#include "base/prefs/pref_registry_simple.h"
+#include "base/prefs/pref_service.h"
+
+namespace metrics {
+
+namespace {
+
+enum IntervalType {
+  FIRST_RUN,
+  DAY_ELAPSED,
+  CLOCK_CHANGED,
+  NUM_INTERVAL_TYPES
+};
+
+void RecordIntervalTypeHistogram(const std::string& histogram_name,
+                                 IntervalType t) {

[Alexei Svitkine (slow), 2014/09/15 21:32:32]

Nit: t -> type

[Steven Holte, 2014/09/15 21:43:09]

Done.

+  base::Histogram::FactoryGet(
+      histogram_name,
+      1,
+      NUM_INTERVAL_TYPES,
+      NUM_INTERVAL_TYPES + 1,
+      base::HistogramBase::kUmaTargetedHistogramFlag)->Add(t);
+}
+
+}  // namespace
+
+DailyEvent::Observer::Observer() {
+}
+
+DailyEvent::Observer::~Observer() {
+}
+
+DailyEvent::DailyEvent(PrefService* pref_service,
+                       const char* pref_name,
+                       const std::string& histogram_name)
+    : pref_service_(pref_service),
+      pref_name_(pref_name),
+      histogram_name_(histogram_name) {
+}
+
+DailyEvent::~DailyEvent() {
+}
+
+// static
+void DailyEvent::RegisterPref(PrefRegistrySimple* registry,
+                              const char* pref_name) {
+  registry->RegisterInt64Pref(pref_name, base::Time().ToInternalValue());
+}
+
+void DailyEvent::AddObserver(scoped_ptr<DailyEvent::Observer> observer) {
+  DVLOG(2) << "DailyEvent observer added.";
+  DCHECK(last_fired_.is_null());
+  observers_.push_back(observer.release());
+}
+
+void DailyEvent::CheckInterval() {
+  base::Time now = base::Time::Now();
+  if (last_fired_.is_null()) {
+    // The first time we call CheckInterval, we read the time stored in prefs.
+    last_fired_ = base::Time::FromInternalValue(
+        pref_service_->GetInt64(pref_name_));
+    DVLOG(1) << "DailyEvent time loaded: "
+             << base::TimeFormatShortDateAndTime(last_fired_);
+    if (last_fired_.is_null()) {
+      DVLOG(1) << "DailyEvent first run.";
+      RecordIntervalTypeHistogram(pref_name_, FIRST_RUN);
+      OnInterval(now);
+      return;
+    }
+  }
+  int days_elapsed = (now - last_fired_).InDays();
+  if (days_elapsed >= 1) {
+    DVLOG(1) << "DailyEvent day elapsed.";
+    RecordIntervalTypeHistogram(pref_name_, DAY_ELAPSED);
+    OnInterval(now);
+  } else if (days_elapsed <= -1) {
+    // The "last fired" time is more than a day in the future, so the clock
+    // must have been changed.
+    DVLOG(1) << "DailyEvent clock change detected.";
+    RecordIntervalTypeHistogram(pref_name_, CLOCK_CHANGED);
+    OnInterval(now);
+  }
+}
+
+void DailyEvent::OnInterval(base::Time now) {
+  DCHECK(!now.is_null());
+  last_fired_ = now;
+  pref_service_->SetInt64(pref_name_, last_fired_.ToInternalValue());
+
+  // Notify all observers
+  for (ScopedVector<DailyEvent::Observer>::iterator it = observers_.begin();
+       it != observers_.end();
+       ++it) {
+    (*it)->OnDailyEvent();
+  }
+}
+
+}  // namespace metrics