prometheus example (open-telemetry#1332)

ci/do_ci.sh

@@ -222,8 +222,8 @@ elif [[ "$1" == "bazel.legacy.test" ]]; then
 elif [[ "$1" == "bazel.noexcept" ]]; then
   # there are some exceptions and error handling code from the Prometheus and Jaeger Clients
   # that make this test always fail. ignore Prometheus and Jaeger exporters in the noexcept here.
-  bazel $BAZEL_STARTUP_OPTIONS build --copt=-fno-exceptions --build_tag_filters=-jaeger $BAZEL_OPTIONS -- //... -//exporters/prometheus/... -//exporters/jaeger/...
-  bazel $BAZEL_STARTUP_OPTIONS test --copt=-fno-exceptions --build_tag_filters=-jaeger $BAZEL_TEST_OPTIONS -- //... -//exporters/prometheus/... -//exporters/jaeger/...
+  bazel $BAZEL_STARTUP_OPTIONS build --copt=-fno-exceptions --build_tag_filters=-jaeger $BAZEL_OPTIONS -- //... -//exporters/prometheus/... -//exporters/jaeger/... -//examples/prometheus/...
+  bazel $BAZEL_STARTUP_OPTIONS test --copt=-fno-exceptions --build_tag_filters=-jaeger $BAZEL_TEST_OPTIONS -- //... -//exporters/prometheus/... -//exporters/jaeger/... -//examples/prometheus/...
   exit 0
 elif [[ "$1" == "bazel.nortti" ]]; then
   # there are some exceptions and error handling code from the Prometheus and Jaeger Clients

examples/CMakeLists.txt

@@ -15,6 +15,9 @@ endif()
 if(WITH_ZIPKIN)
   add_subdirectory(zipkin)
 endif()
+if(WITH_PROMETHEUS AND NOT WITH_METRICS_PREVIEW)
+  add_subdirectory(prometheus)
+endif()
 add_subdirectory(plugin)
 add_subdirectory(simple)
 add_subdirectory(batch)

examples/prometheus/BUILD

@@ -0,0 +1,14 @@
+cc_binary(
+    name = "prometheus_example",
+    srcs = [
+        "main.cc",
+    ],
+    linkopts = ["-pthread"],
+    tags = ["ostream"],
+    deps = [
+        "//api",
+        "//examples/common/metrics_foo_library:common_metrics_foo_library",
+        "//exporters/prometheus:prometheus_exporter",
+        "//sdk/src/metrics",
+    ],
+)

examples/prometheus/CMakeLists.txt

@@ -0,0 +1,5 @@
+include_directories(${CMAKE_SOURCE_DIR}/exporters/prometheus/include)
+add_executable(prometheus_example main.cc)
+target_link_libraries(
+  prometheus_example ${CMAKE_THREAD_LIBS_INIT} opentelemetry_metrics
+  prometheus_exporter opentelemetry_resources common_metrics_foo_library)

examples/prometheus/main.cc

@@ -0,0 +1,118 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef ENABLE_METRICS_PREVIEW
+#  include <memory>
+#  include <thread>
+#  include "opentelemetry/exporters/prometheus/exporter.h"
+#  include "opentelemetry/metrics/provider.h"
+#  include "opentelemetry/sdk/metrics/aggregation/default_aggregation.h"
+#  include "opentelemetry/sdk/metrics/aggregation/histogram_aggregation.h"
+#  include "opentelemetry/sdk/metrics/export/periodic_exporting_metric_reader.h"
+#  include "opentelemetry/sdk/metrics/meter.h"
+#  include "opentelemetry/sdk/metrics/meter_provider.h"
+
+#  ifdef BAZEL_BUILD
+#    include "examples/common/metrics_foo_library/foo_library.h"
+#  else
+#    include "metrics_foo_library/foo_library.h"
+#  endif
+
+namespace metrics_sdk      = opentelemetry::sdk::metrics;
+namespace nostd            = opentelemetry::nostd;
+namespace common           = opentelemetry::common;
+namespace metrics_exporter = opentelemetry::exporter::metrics;
+namespace metrics_api      = opentelemetry::metrics;
+
+namespace
+{
+
+void initMetrics(const std::string &name, const std::string &addr)
+{
+  metrics_exporter::PrometheusExporterOptions opts;
+  if (!addr.empty())
+  {
+    opts.url = addr;
+  }
+  std::puts("PrometheusExporter example program running ...");
+
+  std::unique_ptr<metrics_sdk::MetricExporter> exporter{
+      new metrics_exporter::PrometheusExporter(opts)};
+
+  std::string version{"1.2.0"};
+  std::string schema{"https://opentelemetry.io/schemas/1.2.0"};
+
+  // Initialize and set the global MeterProvider
+  metrics_sdk::PeriodicExportingMetricReaderOptions options;
+  options.export_interval_millis = std::chrono::milliseconds(1000);
+  options.export_timeout_millis  = std::chrono::milliseconds(500);
+  std::unique_ptr<metrics_sdk::MetricReader> reader{
+      new metrics_sdk::PeriodicExportingMetricReader(std::move(exporter), options)};
+  auto provider = std::shared_ptr<metrics_api::MeterProvider>(new metrics_sdk::MeterProvider());
+  auto p        = std::static_pointer_cast<metrics_sdk::MeterProvider>(provider);
+  p->AddMetricReader(std::move(reader));
+
+  // counter view
+  std::string counter_name = name + "_counter";
+  std::unique_ptr<metrics_sdk::InstrumentSelector> instrument_selector{
+      new metrics_sdk::InstrumentSelector(metrics_sdk::InstrumentType::kCounter, counter_name)};
+  std::unique_ptr<metrics_sdk::MeterSelector> meter_selector{
+      new metrics_sdk::MeterSelector(name, version, schema)};
+  std::unique_ptr<metrics_sdk::View> sum_view{
+      new metrics_sdk::View{name, "description", metrics_sdk::AggregationType::kSum}};
+  p->AddView(std::move(instrument_selector), std::move(meter_selector), std::move(sum_view));
+
+  // histogram view
+  std::string histogram_name = name + "_histogram";
+  std::unique_ptr<metrics_sdk::InstrumentSelector> histogram_instrument_selector{
+      new metrics_sdk::InstrumentSelector(metrics_sdk::InstrumentType::kHistogram, histogram_name)};
+  std::unique_ptr<metrics_sdk::MeterSelector> histogram_meter_selector{
+      new metrics_sdk::MeterSelector(name, version, schema)};
+  std::unique_ptr<metrics_sdk::View> histogram_view{
+      new metrics_sdk::View{name, "description", metrics_sdk::AggregationType::kHistogram}};
+  p->AddView(std::move(histogram_instrument_selector), std::move(histogram_meter_selector),
+             std::move(histogram_view));
+  metrics_api::Provider::SetMeterProvider(provider);
+}
+}  // namespace
+
+int main(int argc, char **argv)
+{
+  std::string example_type;
+  std::string addr{"localhost:8080"};
+  if (argc == 1)
+  {
+    std::puts("usage: $prometheus_example <example type> <url>");
+  }
+
+  if (argc >= 2)
+  {
+    example_type = argv[1];
+  }
+  if (argc > 2)
+  {
+    addr = argv[2];
+  }
+
+  std::string name{"prometheus_metric_example"};
+  initMetrics(name, addr);
+
+  if (example_type == "counter")
+  {
+    foo_library::counter_example(name);
+  }
+  else if (example_type == "histogram")
+  {
+    foo_library::histogram_example(name);
+  }
+  else
+  {
+    std::thread counter_example{&foo_library::counter_example, name};
+    std::thread histogram_example{&foo_library::histogram_example, name};
+    counter_example.join();
+    histogram_example.join();
+  }
+}
+#else
+int main() {}
+#endif

examples/prometheus/prometheus.yml

@@ -0,0 +1,16 @@
+global:
+  scrape_interval: 5s
+  scrape_timeout: 2s
+  evaluation_interval: 5s
+alerting:
+  alertmanagers:
+  - follow_redirects: true
+    scheme: http
+    timeout: 5s
+    api_version: v2
+    static_configs:
+    - targets: [localhost:8080]
+scrape_configs:
+  - job_name: otel
+    static_configs:
+      - targets: ['localhost:8080']

examples/prometheus/run.sh

@@ -0,0 +1 @@
+docker run -p 9090:9090 -v $(pwd):/etc/prometheus --network="host" prom/prometheus

exporters/prometheus/include/opentelemetry/exporters/prometheus/exporter.h

@@ -31,7 +31,7 @@ namespace metrics
 inline const std::string GetOtlpDefaultHttpEndpoint()
 {
   constexpr char kPrometheusEndpointEnv[]     = "PROMETHEUS_EXPORTER_ENDPOINT";
-  constexpr char kPrometheusEndpointDefault[] = "http://localhost:8080";
+  constexpr char kPrometheusEndpointDefault[] = "localhost:8080";
 
   auto endpoint = opentelemetry::sdk::common::GetEnvironmentVariable(kPrometheusEndpointEnv);
   return endpoint.size() ? endpoint : kPrometheusEndpointDefault;