Added UMA stats to track the budget for any service worker which receives a

chrome/browser/push_messaging/background_budget_service.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 "chrome/browser/push_messaging/background_budget_service.h"
 
 #include <stdint.h>
 
 #include "base/callback.h"
 #include "base/memory/ptr_util.h"
+#include "base/metrics/histogram_macros.h"
 #include "base/strings/string_number_conversions.h"
 #include "base/strings/string_split.h"
 #include "base/strings/stringprintf.h"
 #include "base/time/clock.h"
 #include "base/time/default_clock.h"
 #include "base/time/time.h"
 #include "chrome/browser/engagement/site_engagement_service.h"
 #include "chrome/browser/profiles/profile.h"
 #include "chrome/common/pref_names.h"
 #include "components/pref_registry/pref_registry_syncable.h"
 #include "components/prefs/pref_service.h"
 #include "components/prefs/scoped_user_pref_update.h"
 
 namespace {
 
 constexpr char kSeparator = '#';
-// We calculate the ratio of the different components of a budget with respect
+
+// Calculate the ratio of the different components of a budget with respect
 // to a maximum time period of 10 days = 864000.0 seconds.
 constexpr double kSecondsToAccumulate = 864000.0;
 
 bool GetBudgetDataFromPrefs(Profile* profile,
                             const GURL& origin,
                             double* old_budget,
                             double* old_ses,
                             double* last_updated) {
   const base::DictionaryValue* map =
       profile->GetPrefs()->GetDictionary(prefs::kBackgroundBudgetMap);
@@ skipping 50 matching lines @@
 }
 
 BackgroundBudgetService::~BackgroundBudgetService() {}
 
 // static
 void BackgroundBudgetService::RegisterProfilePrefs(
     user_prefs::PrefRegistrySyncable* registry) {
   registry->RegisterDictionaryPref(prefs::kBackgroundBudgetMap);
 }
 
+double BackgroundBudgetService::costs_[] = {
+    2.0,  // SILENT_PUSH_COST
+};
+
+// static
+double BackgroundBudgetService::GetBackgroundProcessingCost(CostType type) {
+  return costs_[type];
+}
+
 double BackgroundBudgetService::GetBudget(const GURL& origin) {
   DCHECK_EQ(origin, origin.GetOrigin());
 
   // Get the current SES score, which we'll use to set a new budget.
   SiteEngagementService* service = SiteEngagementService::Get(profile_);
   double ses_score = service->GetScore(origin);
 
   // Get the last used budget data. This is a triple of last calculated time,
   // budget at that time, and Site Engagement Score (ses) at that time.
   double old_budget = 0.0, old_ses = 0.0, last_updated_msec = 0.0;
@@ skipping 21 matching lines @@
   // total period.
   double ses_ratio =
       std::min(1.0, (elapsed.InSeconds() / kSecondsToAccumulate));
   double ses_component = (old_ses + ses_score) / 2 * ses_ratio;
 
   // Budget recalculation consists of a budget carryover component, which
   // rewards sites that don't use all their budgets every day, and a ses
   // component, which gives extra budget to sites that have a high ses score.
   double budget = budget_carryover + ses_component;
   DCHECK_GE(budget, 0.0);
+
+  // Generate histograms for the GetBudget calls which would return "no budget"
+  // or "low budget" if an API was available to app developers.
+  double cost = GetBackgroundProcessingCost(SILENT_PUSH_COST);
+  if (budget < cost)
+    UMA_HISTOGRAM_COUNTS("PushMessaging.SESForNoBudgetOrigin", ses_score);
+  else if (budget < 2.0 * cost)
+    UMA_HISTOGRAM_COUNTS("PushMessaging.SESForLowBudgetOrigin", ses_score);

[Peter Beverloo, 2016/05/17 13:51:01]

To this and the other histograms:

UMA_HISTOGRAM_COUNTS counts 50 buckets in a range of 1 to 1,000,000. We know
|budget| to be in range of [0, 100], so please use UMA_HISTOGRAM_COUNTS_100
instead. That macro counts 50 buckets in a range of 1 to a hundred.

Since buckets have higher granularity for the lower counts, I also wonder what
we gain by having three separate histograms. (I know we discussed this in the
past, but I forgot— sorry!)

We know that-
  (1) PushMessaging.BackgroundBudget will record budgets in the range of [0,
100].
  (2) PushMessaging.SESForNoBudgetOrigin will record budgets in the range of [0,
1.99].
  (3) PushMessaging.SESForLowBudgetOrigin will record budgets in the range of
[2, 3.99].

In addition, lines 151-157 effectively are a layering violation, because it
makes the assumption that budget is being received for push messaging.

Would it make sense to only keep (1)? Michael knows the mechanics of UMA better
than I do.

[Peter Beverloo, 2016/05/17 14:03:23]

Scratch this part, sorry! You're recording the *SES*, not the budget, I need to
read better :).

[harkness, 2016/05/17 15:49:32]

I updated to UMA_HISTOGRAM_COUNTS_100 for all three and moved the SES related
ones into push_messaging_notification_manager.cc

+
   return budget;
 }
 
 void BackgroundBudgetService::StoreBudget(const GURL& origin, double budget) {
   DCHECK_EQ(origin, origin.GetOrigin());
   DCHECK_GE(budget, 0.0);
   DCHECK_LE(budget, SiteEngagementScore::kMaxPoints);
 
   // Get the current SES score to write into the prefs with the new budget.
   SiteEngagementService* service = SiteEngagementService::Get(profile_);
   double ses_score = service->GetScore(origin);
 
   base::Time time = clock_->Now();
   SetBudgetDataInPrefs(profile_, origin, time.ToDoubleT(), budget, ses_score);
 }
 
 // Override the default clock with the specified clock. Only used for testing.
 void BackgroundBudgetService::SetClockForTesting(
     std::unique_ptr<base::Clock> clock) {
   clock_ = std::move(clock);
 }