Example for OTLP gRPC exporter for Metrics. (open-telemetry#1598)

examples/otlp/CMakeLists.txt

@@ -37,3 +37,11 @@ if(WITH_OTLP_HTTP)
       opentelemetry_exporter_otlp_http_log)
   endif()
 endif()
+
+if(WITH_OTLP_GRPC AND NOT WITH_METRICS_PREVIEW)
+  add_executable(example_otlp_metric_grpc grpc_metric_main.cc)
+  target_link_libraries(
+    example_otlp_metric_grpc ${CMAKE_THREAD_LIBS_INIT}
+    common_metrics_foo_library opentelemetry_metrics
+    opentelemetry_exporter_otlp_grpc_metrics)
+endif()

examples/otlp/README.md

@@ -4,21 +4,37 @@ This is an example of how to use the [OpenTelemetry
 Protocol](https://github.com/open-telemetry/opentelemetry-specification/blob/main/specification/protocol/README.md)
 (OTLP) exporter.
 
+### Traces
 The application in `grpc_main.cc` initializes an `OtlpGrpcExporter` instance,
 the application in `http_main.cc` initializes an `OtlpHttpExporter` instance.
-The application in `http_log_main.cc` initializes an `OtlpHttpLogExporter` instance,
-the application in `grpc_log_main.cc` initializes an `OtlpGrpcLogExporter` instance.
 And they register a tracer provider from the [OpenTelemetry
 SDK](https://github.com/open-telemetry/opentelemetry-cpp). The application then
 calls a `foo_library` which has been instrumented using the [OpenTelemetry
 API](https://github.com/open-telemetry/opentelemetry-cpp/tree/main/api).
 
+### Logs
+The application in `http_log_main.cc` initializes an `OtlpHttpLogExporter` instance,
+the application in `grpc_log_main.cc` initializes an `OtlpGrpcLogExporter` instance.
+And they register a logger provider from the [OpenTelemetry
+SDK](https://github.com/open-telemetry/opentelemetry-cpp). The application then
+calls a `logs_foo_library` which has been instrumented using the [OpenTelemetry
+API](https://github.com/open-telemetry/opentelemetry-cpp/tree/main/api).
+
+### Metrics
+The application in `grpc_metrics_main.cc` initializes an `OtlpGrpcMetricExporter` instance.
+And it registers a meter provider from the [OpenTelemetry
+SDK](https://github.com/open-telemetry/opentelemetry-cpp). The application then
+calls a `metrics_foo_library` which has been instrumented using the [OpenTelemetry
+API](https://github.com/open-telemetry/opentelemetry-cpp/tree/main/api).
+
+### Enable SSL/TLS
 To enable TLS authentication for OTLP grpc exporter, SslCredentials can be used
 by specifying the path to client certificate pem file, or the string containing
 this certificate via OtlpGrpcExporterOptions. The path to such a .pem file can be
 provided as a command-line argument alongwith the collector endpoint to the main
 binary invocation above.
 
+### Running OpenTelemetry Collector as docker container
 Resulting spans are exported to the **OpenTelemetry Collector** using the OTLP
 exporter. The OpenTelemetry Collector can be configured to export to other
 backends (see list of [supported
@@ -34,13 +50,13 @@ OpenTelemetry Collector with an OTLP receiver by running:
 - On Unix based systems use:
 
 ```console
-docker run --rm -it -p 4317:4317 -p 4318:4318 -v $(pwd)/examples/otlp:/cfg otel/opentelemetry-collector:0.38.0 --config=/cfg/opentelemetry-collector-config/config.dev.yaml
+docker run --rm -it -p 4317:4317 -p 4318:4318 -v $(pwd)/examples/otlp:/cfg otel/opentelemetry-collector:0.59.0 --config=/cfg/opentelemetry-collector-config/config.dev.yaml
 ```
 
 - On Windows use:
 
 ```console
-docker run --rm -it -p 4317:4317 -p 4318:4318 -v "%cd%/examples/otlp":/cfg otel/opentelemetry-collector:0.38.0 --config=/cfg/opentelemetry-collector-config/config.dev.yaml
+docker run --rm -it -p 4317:4317 -p 4318:4318 -v "%cd%/examples/otlp":/cfg otel/opentelemetry-collector:0.59.0 --config=/cfg/opentelemetry-collector-config/config.dev.yaml
 ```
 
 Note that the OTLP gRPC and HTTP exporters connects to the Collector at `localhost:4317` and `localhost:4318/v1/traces` respectively. This can be changed with first argument from command-line, for example:

examples/otlp/grpc_metric_main.cc

@@ -0,0 +1,97 @@
+// Copyright The OpenTelemetry Authors
+// SPDX-License-Identifier: Apache-2.0
+
+#ifndef ENABLE_METRICS_PREVIEW
+
+#  include "opentelemetry/exporters/otlp/otlp_grpc_metric_exporter_factory.h"
+#  include "opentelemetry/metrics/provider.h"
+#  include "opentelemetry/sdk/metrics/aggregation/default_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"
+
+#  include <memory>
+#  include <thread>
+
+#  ifdef BAZEL_BUILD
+#    include "examples/common/metrics_foo_library/foo_library.h"
+#  else
+#    include "metrics_foo_library/foo_library.h"
+#  endif
+
+namespace metric_sdk    = opentelemetry::sdk::metrics;
+namespace nostd         = opentelemetry::nostd;
+namespace common        = opentelemetry::common;
+namespace metrics_api   = opentelemetry::metrics;
+namespace otlp_exporter = opentelemetry::exporter::otlp;
+
+namespace
+{
+
+otlp_exporter::OtlpGrpcMetricExporterOptions options;
+
+void initMetrics()
+{
+  auto exporter = otlp_exporter::OtlpGrpcMetricExporterFactory::Create(options);
+
+  std::string version{"1.2.0"};
+  std::string schema{"https://opentelemetry.io/schemas/1.2.0"};
+
+  // Initialize and set the global MeterProvider
+  metric_sdk::PeriodicExportingMetricReaderOptions options;
+  options.export_interval_millis = std::chrono::milliseconds(1000);
+  options.export_timeout_millis  = std::chrono::milliseconds(500);
+  std::unique_ptr<metric_sdk::MetricReader> reader{
+      new metric_sdk::PeriodicExportingMetricReader(std::move(exporter), options)};
+  auto provider = std::shared_ptr<metrics_api::MeterProvider>(new metric_sdk::MeterProvider());
+  auto p        = std::static_pointer_cast<metric_sdk::MeterProvider>(provider);
+  p->AddMetricReader(std::move(reader));
+
+  metrics_api::Provider::SetMeterProvider(provider);
+}
+}  // namespace
+
+int main(int argc, char *argv[])
+{
+  std::string example_type;
+  if (argc > 1)
+  {
+    options.endpoint = argv[1];
+    if (argc > 2)
+    {
+      example_type = argv[2];
+      if (argc > 3)
+      {
+        options.use_ssl_credentials         = true;
+        options.ssl_credentials_cacert_path = argv[3];
+      }
+    }
+  }
+  // Removing this line will leave the default noop MetricProvider in place.
+  initMetrics();
+  std::string name{"otlp_grpc_metric_example"};
+
+  if (example_type == "counter")
+  {
+    foo_library::counter_example(name);
+  }
+  else if (example_type == "observable_counter")
+  {
+    foo_library::observable_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 observable_counter_example{&foo_library::observable_counter_example, name};
+    std::thread histogram_example{&foo_library::histogram_example, name};
+
+    counter_example.join();
+    observable_counter_example.join();
+    histogram_example.join();
+  }
+}
+#endif

examples/otlp/opentelemetry-collector-config/config.dev.yaml

@@ -8,8 +8,6 @@ receivers:
         endpoint: 0.0.0.0:4317
       http:
         endpoint: 0.0.0.0:4318
-        cors_allowed_origins:
-        - '*'
 service:
   pipelines:
     traces:
@@ -22,3 +20,8 @@ service:
       - otlp
       exporters:
       - logging
+    metrics:
+      receivers:
+      - otlp
+      exporters:
+      - logging