Added new GroupedHistogram class which can intercept Add() calls and generates

new metrics of the form <metric-name>.<app-name>.

Chromecast startup code registers a specific set of histograms for grouped
collection.

Review URL: https://codereview.chromium.org/751603003

Cr-Commit-Position: refs/heads/master@{#306731}

3 files changed, 209 insertions, 0 deletions

diff --git a/chromecast/base/metrics/cast_metrics_helper.cc b/chromecast/base/metrics/cast_metrics_helper.cc
index b51439f..2a94019 100644
--- a/chromecast/base/metrics/cast_metrics_helper.cc
+++ b/chromecast/base/metrics/cast_metrics_helper.cc
@@ -11,6 +11,7 @@
 #include "base/metrics/histogram.h"
 #include "base/metrics/user_metrics.h"
 #include "chromecast/base/metrics/cast_histograms.h"
+#include "chromecast/base/metrics/grouped_histogram.h"
 
 namespace chromecast {
 namespace metrics {
@@ -67,6 +68,8 @@ void CastMetricsHelper::TagAppStart(const std::string& arg_app_name) {
   app_name_ = arg_app_name;
   app_start_time_ = base::TimeTicks::Now();
   new_startup_time_ = true;
+
+  TagAppStartForGroupedHistograms(app_name_);
 }
 
 void CastMetricsHelper::LogMediaPlay() {
diff --git a/chromecast/base/metrics/grouped_histogram.cc b/chromecast/base/metrics/grouped_histogram.cc
new file mode 100644
index 0000000..8318850
--- /dev/null
+++ b/chromecast/base/metrics/grouped_histogram.cc
@@ -0,0 +1,181 @@
+// 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 "chromecast/base/metrics/grouped_histogram.h"
+
+#include "base/lazy_instance.h"
+#include "base/logging.h"
+#include "base/macros.h"
+#include "base/metrics/histogram.h"
+#include "base/metrics/statistics_recorder.h"
+#include "base/strings/stringprintf.h"
+#include "base/synchronization/lock.h"
+#include "base/time/time.h"
+
+namespace chromecast {
+namespace metrics {
+
+namespace {
+
+const char kAppNameErrorNoApp[] = "ERROR_NO_APP_REGISTERED";
+
+// Current app name guarded by lock.
+struct CurrentAppNameWithLock {
+  base::Lock lock;
+  std::string app_name;
+};
+
+base::LazyInstance<CurrentAppNameWithLock> g_current_app =
+    LAZY_INSTANCE_INITIALIZER;
+
+std::string GetAppName() {
+  base::AutoLock lock(g_current_app.Get().lock);
+  const std::string& app_name = g_current_app.Get().app_name;
+  return app_name.empty() ? kAppNameErrorNoApp : app_name;
+}
+
+struct HistogramArgs {
+  const char* name;
+  int minimum;
+  int maximum;
+  size_t bucket_count;
+};
+
+// List of metrics to collect using a GroupedHistogram.
+//
+// When adding more Histograms to this list, find the source of the
+// Histogram and look for the construction arguments it uses to add it in.
+const HistogramArgs kHistogramsToGroup[] = {
+  {
+    "DNS.TotalTime",
+    1,
+    1000 * 60 * 60,
+    100,
+  },
+  {
+    "Net.DNS_Resolution_And_TCP_Connection_Latency2",
+    1,
+    1000 * 60 * 10,
+    100,
+  },
+  {
+    "Net.SSL_Connection_Latency2",
+    1,
+    1000 * 60,
+    100,
+  },
+  {
+    "Net.TCP_Connection_Latency",
+    1,
+    1000 * 60 * 10,
+    100,
+  },
+  {
+    "Net.HttpJob.TotalTime",
+    1,
+    1000 * 10,
+    50,
+  },
+};
+
+// This class is used to override a Histogram to generate per-app metrics.
+// It intercepts calls to Add() for a given metric and generates new metrics
+// of the form "<metric-name>.<app-name>".
+class GroupedHistogram : public base::Histogram {
+ public:
+  GroupedHistogram(const std::string& metric_to_override,
+                   Sample minimum,
+                   Sample maximum,
+                   const base::BucketRanges* ranges)
+      : Histogram(metric_to_override, minimum, maximum, ranges),
+        metric_to_group_(metric_to_override),
+        minimum_(minimum),
+        maximum_(maximum),
+        bucket_count_(ranges->bucket_count()) {
+  }
+
+  ~GroupedHistogram() override {
+  }
+
+  // base::Histogram implementation:
+  void Add(Sample value) override {
+    Histogram::Add(value);
+    std::string name(base::StringPrintf("%s.%s",
+                                        histogram_name().c_str(),
+                                        GetAppName().c_str()));
+    HistogramBase* grouped_histogram =
+        base::Histogram::FactoryGet(name,
+                                    minimum_,
+                                    maximum_,
+                                    bucket_count_,
+                                    flags());
+    DCHECK(grouped_histogram);
+    grouped_histogram->Add(value);
+  }
+
+ private:
+  // Saved construction arguments for reconstructing the Histogram later (with
+  // a suffixed app name).
+  std::string metric_to_group_;
+  Sample minimum_;
+  Sample maximum_;
+  size_t bucket_count_;
+
+  DISALLOW_COPY_AND_ASSIGN(GroupedHistogram);
+};
+
+// Registers a GroupedHistogram with StatisticsRecorder.  Must be called
+// before any Histogram of the same name has been used.
+// It acts similarly to Histogram::FactoryGet but checks that
+// the histogram is being newly created and does not already exist.
+void PreregisterHistogram(const std::string& name,
+                          GroupedHistogram::Sample minimum,
+                          GroupedHistogram::Sample maximum,
+                          size_t bucket_count,
+                          int32 flags) {
+  DCHECK(base::StatisticsRecorder::IsActive());
+  DCHECK(base::Histogram::InspectConstructionArguments(
+      name, &minimum, &maximum, &bucket_count));
+  DCHECK(!base::StatisticsRecorder::FindHistogram(name))
+      << "Failed to preregister " << name << ", Histogram already exists.";
+
+  // To avoid racy destruction at shutdown, the following will be leaked.
+  base::BucketRanges* ranges = new base::BucketRanges(bucket_count + 1);
+  base::Histogram::InitializeBucketRanges(minimum, maximum, ranges);
+  const base::BucketRanges* registered_ranges =
+      base::StatisticsRecorder::RegisterOrDeleteDuplicateRanges(ranges);
+
+  GroupedHistogram* tentative_histogram =
+      new GroupedHistogram(name, minimum, maximum, registered_ranges);
+
+  tentative_histogram->SetFlags(flags);
+  base::HistogramBase* histogram =
+      base::StatisticsRecorder::RegisterOrDeleteDuplicate(tentative_histogram);
+
+  DCHECK_EQ(histogram, tentative_histogram);
+  DCHECK_EQ(base::HISTOGRAM, histogram->GetHistogramType());
+  DCHECK(histogram->HasConstructionArguments(minimum, maximum, bucket_count));
+}
+
+} // namespace
+
+void PreregisterAllGroupedHistograms() {
+  base::StatisticsRecorder::Initialize();
+  for (size_t i = 0; i < arraysize(kHistogramsToGroup); ++i) {
+    PreregisterHistogram(
+        kHistogramsToGroup[i].name,
+        kHistogramsToGroup[i].minimum,
+        kHistogramsToGroup[i].maximum,
+        kHistogramsToGroup[i].bucket_count,
+        base::HistogramBase::kUmaTargetedHistogramFlag);
+  }
+}
+
+void TagAppStartForGroupedHistograms(const std::string& app_name) {
+  base::AutoLock lock(g_current_app.Get().lock);
+  g_current_app.Get().app_name = app_name;
+}
+
+} // namespace metrics
+} // namespace chromecast
diff --git a/chromecast/base/metrics/grouped_histogram.h b/chromecast/base/metrics/grouped_histogram.h
new file mode 100644
index 0000000..b5202e6
--- /dev/null
+++ b/chromecast/base/metrics/grouped_histogram.h
@@ -0,0 +1,25 @@
+// 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.
+
+#ifndef CHROMECAST_BASE_METRICS_GROUPED_HISTOGRAM_H_
+#define CHROMECAST_BASE_METRICS_GROUPED_HISTOGRAM_H_
+
+#include <string>
+
+namespace chromecast {
+namespace metrics {
+
+// Registers a predefined list of histograms to be collected per-app.  Must be
+// called before any histograms of the same name are used or registration will
+// fail.
+void PreregisterAllGroupedHistograms();
+
+// Sets the current app name to be used for subsequent grouped histogram
+// samples (a new metric is generated with the app name as a suffix).
+void TagAppStartForGroupedHistograms(const std::string& app_name);
+
+} // namespace metrics
+} // namespace chromecast
+
+#endif // CHROMECAST_BASE_METRICS_GROUPED_HISTOGRAM_H_