Add C++ Prometheus Exporter Example Program

examples/CMakeLists.txt

@@ -2,3 +2,4 @@ add_subdirectory(plugin)
 add_subdirectory(simple)
 add_subdirectory(batch)
 add_subdirectory(metrics_simple)
+add_subdirectory(prometheus_exporter)

examples/prometheus_exporter/BUILD

@@ -0,0 +1,25 @@
+# Copyright 2020, OpenTelemetry 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.
+
+cc_binary(
+    name = "prometheus_exporter_example",
+    srcs = [
+        "main.cc",
+    ],
+    deps = [
+        "//exporters/prometheus:prometheus_exporter",
+        "//exporters/prometheus:prometheus_collector",
+        "//exporters/prometheus:prometheus_utils",
+    ],
+)

examples/prometheus_exporter/CMakeLists.txt

@@ -0,0 +1,6 @@
+include_directories(${CMAKE_SOURCE_DIR}/exporters/prometheus/include)
+find_package(prometheus-cpp CONFIG REQUIRED)
+
+add_executable(prom_exp_example main.cc)
+target_link_libraries(prom_exp_example ${CMAKE_THREAD_LIBS_INIT}
+        prometheus_exporter prometheus-cpp::pull)

examples/prometheus_exporter/README.md

@@ -0,0 +1,66 @@
+# Prometheus Exporter Example
+
+In this example, the application in `main.cc` initializes the Prometheus exporter and exports 6 different OTel Aggregator to Prometheus. 
+Here are more detailed explanations of it.
+
+## Start Prometheus Instance
+Start a Prometheus instance with Docker:
+```shell script
+docker run prom/prometheus
+```
+Add Prometheus Exporter job configuration to `~/docker/prometheus/prometheus.yml`
+```yaml
+scrape_configs:
+  # ...
+  # other jobs
+  # ...
+  - job_name: 'test_prom_exporter'
+    static_configs:
+      - targets: ['docker.for.mac.localhost:8080']
+```
+Restart Prometheus instance and specify configuration file
+```shell script
+docker run -d --expose 8080 \
+  -p 9090:9090 \
+  -v ~/docker/prometheus/prometheus.yml:/etc/prometheus/prometheus.yml  \
+  prom/prometheus
+```
+
+## Run Example Program
+
+To run the program, you must provide a command line argument to specify which Aggregator Kind you want to run the demo. The six choices are:
+```
+counter, gauge, mmsc, histogram, exact, sketch
+```
+
+Run with Bazel:
+```shell
+bazel build //examples/prometheus_exporter:prometheus_exporter_example
+bazel-bin/examples/prometheus_exporter/prometheus_exporter_example histogram
+```
+The `histogram` command line argument is the argument `agg` to specify.
+
+For example, if we choose Histogram, this is what it would look like to build and execute the example:
+```
+$ bazel build //examples/prometheus_exporter:prometheus_exporter_example
+$ bazel-bin/examples/prometheus_exporter/prometheus_exporter_example histogram 
+Prometheus Exporter example program running on localhost:8080...
+Running histogram example program...
+```
+The example program generates 4 metrics every second, and exports every 15 seconds.
+
+Wait for a while, and visit `localhost:9090`. Choose the name of metrics to view the graphs.
+
+Histogram Count: Each batch of metric data contains 60 metrics
+
+![IMG](./images/count.png)
+
+Histogram Sum:
+
+![IMG](./images/sum.png)
+
+Histogram Buckets:
+
+![IMG](./images/buckets.png)
+
+The process is similar for other OTel Aggregator.

examples/prometheus_exporter/main.cc

@@ -0,0 +1,173 @@
+#include "opentelemetry/exporters/prometheus/prometheus_collector.h"
+#include "opentelemetry/exporters/prometheus/prometheus_exporter.h"
+#include "opentelemetry/sdk/metrics/aggregator/counter_aggregator.h"
+#include "opentelemetry/sdk/metrics/aggregator/exact_aggregator.h"
+#include "opentelemetry/sdk/metrics/aggregator/gauge_aggregator.h"
+#include "opentelemetry/sdk/metrics/aggregator/histogram_aggregator.h"
+#include "opentelemetry/sdk/metrics/aggregator/min_max_sum_count_aggregator.h"
+#include "opentelemetry/sdk/metrics/aggregator/sketch_aggregator.h"
+
+#include <chrono>
+#include <cstdlib>
+#include <iostream>
+#include <string>
+#include <thread>
+
+namespace prom_exp   = opentelemetry::exporter::prometheus;
+namespace metric_sdk = opentelemetry::sdk::metrics;
+namespace metric_api = opentelemetry::metrics;
+
+namespace
+{
+  template <typename T>
+  metric_sdk::Record get_record(const std::string &type,
+                                int version,
+                                const std::string &label,
+                                std::shared_ptr<metric_sdk::Aggregator<T>> aggregator)
+  {
+    std::string name = "test-" + type + "-metric-record-v_" + std::to_string(version) + ".0";
+    std::string desc = "this is a test " + type + " metric record";
+    metric_sdk::Record record(name, desc, label, aggregator);
+    return record;
+  }
+
+  template <typename T>
+  void do_example(const std::shared_ptr<metric_sdk::Aggregator<T>> &aggregator,
+                  std::vector<metric_sdk::Record> collection,
+                  const metric_sdk::Record &record,
+                  prom_exp::PrometheusExporter &exporter)
+  {
+    int counter = 0;
+    while (true)
+    {
+      int val = (rand() % 100) + 1;
+      aggregator->update(val);
+
+      counter++;
+      std::this_thread::sleep_for(std::chrono::milliseconds(250));
+
+      if (counter % 60 == 0)
+      {
+        // add record to collection and export the collection
+        aggregator->checkpoint();
+        collection.emplace_back(record);
+        exporter.Export(collection);
+        counter = 0;
+      }
+    }
+  }
+
+  void counter_example(prom_exp::PrometheusExporter &exporter)
+  {
+    auto aggregator = std::shared_ptr<metric_sdk::Aggregator<int>>(
+        new metric_sdk::CounterAggregator<int>(metric_api::InstrumentKind::Counter));
+
+    // collection of records to export
+    std::vector<metric_sdk::Record> collection;
+    auto record = get_record("counter", 1, "{label-1:v1,label2:v2,}", aggregator);
+    do_example(aggregator, collection, record, exporter);
+  }
+
+  void gauge_example(prom_exp::PrometheusExporter &exporter)
+  {
+    auto aggregator = std::shared_ptr<metric_sdk::Aggregator<int>>(
+        new metric_sdk::GaugeAggregator<int>(metric_api::InstrumentKind::Counter));
+
+    // collection of records to export
+    std::vector<metric_sdk::Record> collection;
+    auto record = get_record("gauge", 1, "{label-1:v1,label2:v2,}", aggregator);
+    do_example(aggregator, collection, record, exporter);
+  }
+
+  void mmsc_example(prom_exp::PrometheusExporter &exporter)
+  {
+    auto aggregator = std::shared_ptr<metric_sdk::Aggregator<double>>(
+        new metric_sdk::MinMaxSumCountAggregator<double>(metric_api::InstrumentKind::Counter));
+
+    // collection of records to export
+    std::vector<metric_sdk::Record> collection;
+    auto record = get_record("mmsc", 1, "{label-1:v1,label2:v2,}", aggregator);
+    do_example(aggregator, collection, record, exporter);
+  }
+
+  void histogram_example(prom_exp::PrometheusExporter &exporter)
+  {
+    std::vector<double> boundaries{10, 20, 30, 40, 50};
+    auto aggregator = std::shared_ptr<metric_sdk::Aggregator<int>>(
+        new metric_sdk::HistogramAggregator<int>(metric_api::InstrumentKind::Counter, boundaries));
+
+    // collection of records to export
+    std::vector<metric_sdk::Record> collection;
+    auto record = get_record("histogram", 1, "{label-1:v1,label2:v2,}", aggregator);
+    do_example(aggregator, collection, record, exporter);
+  }
+
+  void exact_example(prom_exp::PrometheusExporter &exporter)
+  {
+    auto aggregator = std::shared_ptr<metric_sdk::Aggregator<int>>(
+        new metric_sdk::ExactAggregator<int>(metric_api::InstrumentKind::Counter, true));
+
+    // collection of records to export
+    std::vector<metric_sdk::Record> collection;
+    auto record = get_record("exact", 1, "{label-1:v1,label2:v2,}", aggregator);
+    do_example(aggregator, collection, record, exporter);
+  }
+
+  void sketch_example(prom_exp::PrometheusExporter &exporter)
+  {
+    auto aggregator = std::shared_ptr<metric_sdk::Aggregator<int>>(
+        new metric_sdk::SketchAggregator<int>(metric_api::InstrumentKind::Counter, true));
+
+    // collection of records to export
+    std::vector<metric_sdk::Record> collection;
+    auto record = get_record("sketch", 1, "{label-1:v1,label2:v2,}", aggregator);
+    do_example(aggregator, collection, record, exporter);
+  }
+}
+int main(int argc, char** argv)
+{
+  if(argc != 2) {
+    std::cout << "invalid number of command line arguments\n";
+    return 0;
+  }
+
+  std::string agg(argv[1]);
+
+  std::string address = "localhost:8080";
+  prom_exp::PrometheusExporter exporter{address};
+
+  std::cout << "Prometheus Exporter example program running on " << address << "...\n";
+  std::cout << "Running " << agg << " example program...\n";
+
+  if (agg == "counter")
+  {
+    counter_example(exporter);
+  }
+  else if (agg == "gauge")
+  {
+    gauge_example(exporter);
+  }
+  else if (agg == "mmsc")
+  {
+    mmsc_example(exporter);
+  }
+  else if (agg == "histogram")
+  {
+    histogram_example(exporter);
+  }
+  else if (agg == "exact")
+  {
+    exact_example(exporter);
+  }
+  else if (agg == "sketch")
+  {
+    sketch_example(exporter);
+  }
+  else
+  {
+    std::cout << "invalid aggregator kind given\n";
+  }
+
+
+  return 0;
+}