metrics: add prometheus exporter

ci/do_ci.sh

@@ -91,8 +91,10 @@ elif [[ "$1" == "cmake.legacy.test" ]]; then
   ${SRC_DIR}/tools/build-gtest.sh
   ${SRC_DIR}/tools/build-benchmark.sh
   cmake -DCMAKE_BUILD_TYPE=Debug  \
+        -DWITH_PROMETHEUS=ON \
         -DCMAKE_CXX_FLAGS="-Werror" \
         -DCMAKE_CXX_STANDARD=11 \
+        -DCMAKE_EXE_LINKER_FLAGS="-lpthread" \
         "${SRC_DIR}"
   make
   make test

exporters/prometheus/BUILD

@@ -14,6 +14,26 @@
 
 package(default_visibility = ["//visibility:public"])
 
+cc_library(
+    name = "prometheus_exporter",
+    srcs = [
+        "src/prometheus_exporter.cc",
+    ],
+    hdrs = [
+        "include/opentelemetry/exporters/prometheus/prometheus_collector.h",
+        "include/opentelemetry/exporters/prometheus/prometheus_exporter.h",
+        "include/opentelemetry/exporters/prometheus/prometheus_exporter_utils.h",
+    ],
+    strip_include_prefix = "include",
+    deps = [
+        ":prometheus_collector",
+        "//api",
+        "//sdk:headers",
+        "@com_github_jupp0r_prometheus_cpp//core",
+        "@com_github_jupp0r_prometheus_cpp//pull",
+    ],
+)
+
 cc_library(
     name = "prometheus_collector",
     srcs = [
@@ -48,6 +68,17 @@ cc_library(
     ],
 )
 
+cc_test(
+    name = "prometheus_exporter_test",
+    srcs = [
+        "test/prometheus_exporter_test.cc",
+    ],
+    deps = [
+        ":prometheus_exporter",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_test(
     name = "prometheus_collector_test",
     srcs = [

exporters/prometheus/CMakeLists.txt

@@ -14,8 +14,9 @@
 
 find_package(prometheus-cpp CONFIG REQUIRED)
 
-add_library(prometheus_exporter src/prometheus_collector.cc
-                                src/prometheus_exporter_utils.cc)
+add_library(
+  prometheus_exporter src/prometheus_exporter.cc src/prometheus_collector.cc
+                      src/prometheus_exporter_utils.cc)
 
 target_include_directories(
   prometheus_exporter

exporters/prometheus/include/opentelemetry/exporters/prometheus/prometheus_exporter.h

@@ -0,0 +1,109 @@
+/*
+ * Copyright The 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.
+ */
+
+#pragma once
+
+#include <memory>
+#include <string>
+#include <vector>
+
+#include "opentelemetry/sdk/metrics/exporter.h"
+#include "opentelemetry/sdk/metrics/record.h"
+#include "opentelemetry/version.h"
+#include "prometheus/exposer.h"
+#include "prometheus_collector.h"
+
+/**
+ * This class is an implementation of the MetricsExporter interface and
+ * exports Prometheus metrics data. Functions in this class should be
+ * called by the Controller in our data pipeline.
+ */
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace prometheus
+{
+class PrometheusExporter : public sdk::metrics::MetricsExporter
+{
+public:
+  /**
+   * Constructor - binds an exposer and collector to the exporter
+   * @param address: an address for an exposer that exposes
+   *  an HTTP endpoint for the exporter to connect to
+   */
+  PrometheusExporter(std::string &address);
+
+  /**
+   * Exports a batch of Metric Records.
+   * @param records: a collection of records to export
+   * @return: returns a ReturnCode detailing a success, or type of failure
+   */
+  sdk::metrics::ExportResult Export(
+      const std::vector<sdk::metrics::Record> &records) noexcept override;
+
+  /**
+   * Shuts down the exporter and does cleanup.
+   * Since Prometheus is a pull based interface,
+   * we cannot serve data remaining in the intermediate
+   * collection to to client an HTTP request being sent,
+   * so we flush the data.
+   */
+  void Shutdown() noexcept;
+
+  /**
+   * @return: returns a shared_ptr to
+   * the PrometheusCollector instance
+   */
+  std::shared_ptr<PrometheusCollector> &GetCollector();
+
+  /**
+   * @return: Gets the shutdown status of the exporter
+   */
+  bool IsShutdown() const;
+
+private:
+  /**
+   * exporter shutdown status
+   */
+  bool is_shutdown_;
+
+  /**
+   * Pointer to a
+   * PrometheusCollector instance
+   */
+  std::shared_ptr<PrometheusCollector> collector_;
+
+  /**
+   * Pointer to an
+   * Exposer instance
+   */
+  std::unique_ptr<::prometheus::Exposer> exposer_;
+
+  /**
+   * friend class for testing
+   */
+  friend class PrometheusExporterTest;
+
+  /**
+   * PrometheusExporter constructor with no parameters
+   * Used for testing only
+   */
+  PrometheusExporter();
+};
+}  // namespace prometheus
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE

exporters/prometheus/src/prometheus_exporter.cc

@@ -0,0 +1,106 @@
+/*
+ * Copyright The 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.
+ */
+
+#include "opentelemetry/exporters/prometheus/prometheus_exporter.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace prometheus
+{
+/**
+ * Constructor - binds an exposer and collector to the exporter
+ * @param address: an address for an exposer that exposes
+ *  an HTTP endpoint for the exporter to connect to
+ */
+PrometheusExporter::PrometheusExporter(std::string &address) : is_shutdown_(false)
+{
+  exposer_   = std::unique_ptr<::prometheus::Exposer>(new ::prometheus::Exposer{address});
+  collector_ = std::shared_ptr<PrometheusCollector>(new PrometheusCollector);
+
+  exposer_->RegisterCollectable(collector_);
+}
+
+/**
+ * PrometheusExporter constructor with no parameters
+ * Used for testing only
+ */
+PrometheusExporter::PrometheusExporter() : is_shutdown_(false)
+{
+  collector_ = std::unique_ptr<PrometheusCollector>(new PrometheusCollector);
+}
+
+/**
+ * Exports a batch of Metric Records.
+ * @param records: a collection of records to export
+ * @return: returns a ReturnCode detailing a success, or type of failure
+ */
+sdk::metrics::ExportResult PrometheusExporter::Export(
+    const std::vector<sdk::metrics::Record> &records) noexcept
+{
+  if (is_shutdown_)
+  {
+    return sdk::metrics::ExportResult::kFailure;
+  }
+  else if (records.empty())
+  {
+    return sdk::metrics::ExportResult::kFailureInvalidArgument;
+  }
+  else if (collector_->GetCollection().size() + records.size() > collector_->GetMaxCollectionSize())
+  {
+    return sdk::metrics::ExportResult::kFailureFull;
+  }
+  else
+  {
+    collector_->AddMetricData(records);
+    return sdk::metrics::ExportResult::kSuccess;
+  }
+}
+
+/**
+ * Shuts down the exporter and does cleanup.
+ * Since Prometheus is a pull based interface,
+ * we cannot serve data remaining in the intermediate
+ * collection to to client an HTTP request being sent,
+ * so we flush the data.
+ */
+void PrometheusExporter::Shutdown() noexcept
+{
+  is_shutdown_ = true;
+
+  collector_->GetCollection().clear();
+}
+
+/**
+ * @return: returns a shared_ptr to
+ * the PrometheusCollector instance
+ */
+std::shared_ptr<PrometheusCollector> &PrometheusExporter::GetCollector()
+{
+  return collector_;
+}
+
+/**
+ * @return: Gets the shutdown status of the exporter
+ */
+bool PrometheusExporter::IsShutdown() const
+{
+  return is_shutdown_;
+}
+
+}  // namespace prometheus
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE

exporters/prometheus/test/CMakeLists.txt

@@ -1,4 +1,5 @@
-foreach(testname prometheus_collector_test prometheus_exporter_utils_test)
+foreach(testname prometheus_exporter_test prometheus_collector_test
+                 prometheus_exporter_utils_test)
   add_executable(${testname} "${testname}.cc")
   target_link_libraries(
     ${testname} ${GTEST_BOTH_LIBRARIES} ${CMAKE_THREAD_LIBS_INIT}