Add a benchmark for stats. (#16)

Presently covering aggregation / aggregation window combinations
and varying numbers of views.

Author: g-easy

opencensus/stats/BUILD

@@ -205,3 +205,23 @@ cc_test(
         "@com_google_googletest//:gtest_main",
     ],
 )
+
+# Benchmarks
+# ========================================================================= #
+cc_binary(
+    name = "stats_manager_benchmark",
+    testonly = 1,
+    srcs = ["internal/stats_manager_benchmark.cc"],
+    copts = TEST_COPTS,
+    linkopts = ["-pthread"],  # Required for absl/synchronization bits.
+    linkstatic = 1,
+    deps = [
+        ":core",
+        ":export",
+        ":recording",
+        "@com_google_absl//absl/memory",
+        "@com_google_absl//absl/strings",
+        "@com_google_absl//absl/time",
+        "@com_google_benchmark//:benchmark",
+    ],
+)

opencensus/stats/internal/stats_manager_benchmark.cc

@@ -0,0 +1,120 @@
+// Copyright 2018, OpenCensus Authors
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+#include <memory>
+
+#include "absl/memory/memory.h"
+#include "absl/strings/str_cat.h"
+#include "absl/time/time.h"
+#include "benchmark/benchmark.h"
+#include "opencensus/stats/measure.h"
+#include "opencensus/stats/measure_registry.h"
+#include "opencensus/stats/recording.h"
+#include "opencensus/stats/view.h"
+
+namespace opencensus {
+namespace stats {
+namespace {
+
+// Generates unique measure names. Since the registry does not support
+// unregistering, all measure names must be different across test cases.
+// In the present implementation, the number of measures should not affect the
+// performance of other measures--in the absence of the ability to reset state,
+// that is the best we can do.
+std::string MakeUniqueName() {
+  static int counter;
+  return absl::StrCat("name", counter++);
+}
+
+// A set of utility types that allow "templating" a benchmark by
+// Aggregation/AggregationWindow.
+struct SumAggregation {
+  Aggregation operator()(const BucketBoundaries& bucketer) {
+    return Aggregation::Sum();
+  }
+};
+struct CountAggregation {
+  Aggregation operator()(const BucketBoundaries& bucketer) {
+    return Aggregation::Count();
+  }
+};
+struct DistributionAggregation {
+  Aggregation operator()(const BucketBoundaries& bucketer) {
+    return Aggregation::Distribution(bucketer);
+  }
+};
+struct CumulativeWindow {
+  AggregationWindow operator()(absl::Duration interval) {
+    return AggregationWindow::Cumulative();
+  }
+};
+struct IntervalWindow {
+  AggregationWindow operator()(absl::Duration interval) {
+    return AggregationWindow::Interval(interval);
+  }
+};
+
+// Benchmarks recording against various numbers of views on a single measure
+// with a small number of tags.
+template <class AggregationFactory, class AggregationWindowFactory>
+void BM_Record(benchmark::State& state) {
+  const std::string tag_key_1 = "tag_key_1";
+  const std::string tag_key_2 = "tag_key_2";
+  const std::string measure_name = MakeUniqueName();
+  MeasureDouble measure = MeasureRegistry::RegisterDouble(measure_name, "", "");
+  std::vector<std::unique_ptr<View>> views;
+  for (int i = 0; i < state.range(0); ++i) {
+    // The view_key_* tag key is necessary to prevent these from being merged by
+    // the StatsManager.
+    const ViewDescriptor descriptor =
+        ViewDescriptor()
+            .set_measure(measure_name)
+            .set_name("count")
+            .set_aggregation(
+                AggregationFactory()(BucketBoundaries::Exponential(10, 10, 2)))
+            .set_aggregation_window(AggregationWindowFactory()(absl::Hours(1)))
+            .add_column(tag_key_1)
+            .add_column(absl::StrCat("view_key_", i));
+    views.push_back(absl::make_unique<View>(descriptor));
+  }
+  std::vector<std::string> tag_values(100);
+  for (int i = 0; i < 100; ++i) {
+    tag_values[i] = absl::StrCat("value", i);
+  }
+  int iteration = 0;
+  while (state.KeepRunning()) {
+    Record({{measure, static_cast<double>(iteration)}},
+           {{tag_key_1, tag_values[iteration % tag_values.size()]},
+            {tag_key_2, ""}});
+    ++iteration;
+  }
+}
+BENCHMARK_TEMPLATE2(BM_Record, SumAggregation, CumulativeWindow)->Range(1, 16);
+BENCHMARK_TEMPLATE2(BM_Record, SumAggregation, IntervalWindow)->Range(1, 16);
+BENCHMARK_TEMPLATE2(BM_Record, CountAggregation, CumulativeWindow)
+    ->Range(1, 16);
+BENCHMARK_TEMPLATE2(BM_Record, CountAggregation, IntervalWindow)->Range(1, 16);
+BENCHMARK_TEMPLATE2(BM_Record, DistributionAggregation, CumulativeWindow)
+    ->Range(1, 16);
+BENCHMARK_TEMPLATE2(BM_Record, DistributionAggregation, IntervalWindow)
+    ->Range(1, 16);
+
+// TODO: Other useful benchmarks:
+//  - Multithreaded recording against one/different measures.
+//  - Recording with parameterized numbers of tag keys.
+
+}  // namespace
+}  // namespace stats
+}  // namespace opencensus
+BENCHMARK_MAIN();