Add Prometheus Exporter: Step 2 - PrometheusCollector

ci/do_ci.sh

@@ -106,8 +106,10 @@ elif [[ "$1" == "bazel.test" ]]; then
   bazel test $BAZEL_TEST_OPTIONS //...
   exit 0
 elif [[ "$1" == "bazel.legacy.test" ]]; then
-  bazel build $BAZEL_OPTIONS -- //... -//exporters/otlp/...
-  bazel test $BAZEL_TEST_OPTIONS -- //... -//exporters/otlp/...
+  # we uses C++ future and async() function to test the Prometheus Exporter functionality,
+  # that make this test always fail. ignore Prometheus exporter here.
+  bazel build $BAZEL_OPTIONS -- //... -//exporters/otlp/... -//exporters/prometheus/...
+  bazel test $BAZEL_TEST_OPTIONS -- //... -//exporters/otlp/... -//exporters/prometheus/...
   exit 0
 elif [[ "$1" == "bazel.noexcept" ]]; then
   # there are some exceptions and error handling code from the Prometheus Client

exporters/prometheus/BUILD

@@ -14,6 +14,24 @@
 
 package(default_visibility = ["//visibility:public"])
 
+cc_library(
+    name = "prometheus_collector",
+    srcs = [
+        "src/prometheus_collector.cc",
+    ],
+    hdrs = [
+        "include/opentelemetry/exporters/prometheus/prometheus_collector.h",
+        "include/opentelemetry/exporters/prometheus/prometheus_exporter_utils.h",
+    ],
+    strip_include_prefix = "include",
+    deps = [
+        ":prometheus_utils",
+        "//api",
+        "//sdk:headers",
+        "@com_github_jupp0r_prometheus_cpp//core",
+    ],
+)
+
 cc_library(
     name = "prometheus_utils",
     srcs = [
@@ -30,6 +48,17 @@ cc_library(
     ],
 )
 
+cc_test(
+    name = "prometheus_collector_test",
+    srcs = [
+        "test/prometheus_collector_test.cc",
+    ],
+    deps = [
+        ":prometheus_collector",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
 cc_test(
     name = "prometheus_exporter_utils_test",
     srcs = [

exporters/prometheus/CMakeLists.txt

@@ -15,7 +15,9 @@
 include_directories(include)
 
 find_package(prometheus-cpp CONFIG REQUIRED)
-add_library(prometheus_exporter src/prometheus_exporter_utils.cc)
+
+add_library(prometheus_exporter src/prometheus_collector.cc
+                                src/prometheus_exporter_utils.cc)
 
 if(BUILD_TESTING)
   add_subdirectory(test)

exporters/prometheus/include/opentelemetry/exporters/prometheus/prometheus_collector.h

@@ -0,0 +1,100 @@
+/*
+ * 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 <mutex>
+#include <vector>
+
+#include "opentelemetry/sdk/metrics/record.h"
+#include "prometheus/collectable.h"
+#include "prometheus/metric_family.h"
+#include "prometheus_exporter_utils.h"
+
+namespace prometheus_client = ::prometheus;
+namespace metric_sdk        = opentelemetry::sdk::metrics;
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace prometheus
+{
+/**
+ * The Prometheus Collector maintains the intermediate collection in Prometheus Exporter
+ */
+class PrometheusCollector : public prometheus_client::Collectable
+{
+public:
+  /**
+   * Default Constructor.
+   *
+   * This constructor initializes the collection for metrics to export
+   * in this class with default capacity
+   */
+  explicit PrometheusCollector(int max_collection_size = 2048);
+
+  /**
+   * Collects all metrics data from metricsToCollect collection.
+   *
+   * @return all metrics in the metricsToCollect snapshot
+   */
+  std::vector<prometheus_client::MetricFamily> Collect() const override;
+
+  /**
+   * This function is called by export() function and add the collection of
+   * records to the metricsToCollect collection
+   *
+   * @param records a collection of records to add to the metricsToCollect collection
+   */
+  void AddMetricData(const std::vector<metric_sdk::Record> &records);
+
+  /**
+   * Get the current collection in the collector.
+   *
+   * @return the current metricsToCollect collection
+   */
+  std::vector<metric_sdk::Record> GetCollection();
+
+  /**
+   * Gets the maximum size of the collection.
+   *
+   * @return max collection size
+   */
+  int GetMaxCollectionSize() const;
+
+private:
+  /**
+   * Collection of metrics data from the export() function, and to be export
+   * to user when they send a pull request. This collection is a pointer
+   * to a collection so Collect() is able to clear the collection, even
+   * though it is a const function.
+   */
+  std::unique_ptr<std::vector<metric_sdk::Record>> metrics_to_collect_;
+
+  /**
+   * Maximum size of the metricsToCollect collection.
+   */
+  int max_collection_size_;
+
+  /*
+   * Lock when operating the metricsToCollect collection
+   */
+  mutable std::mutex collection_lock_;
+};
+}  // namespace prometheus
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE

exporters/prometheus/src/prometheus_collector.cc

@@ -0,0 +1,175 @@
+/*
+ * 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 <iostream>
+
+#include "opentelemetry/exporters/prometheus/prometheus_collector.h"
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace prometheus
+{
+/**
+ * Default Constructor.
+ *
+ * This constructor initializes the collection for metrics to export
+ * in this class with default capacity
+ */
+PrometheusCollector::PrometheusCollector(int max_collection_size)
+    : max_collection_size_(max_collection_size)
+{
+  metrics_to_collect_ =
+      std::unique_ptr<std::vector<metric_sdk::Record>>(new std::vector<metric_sdk::Record>);
+}
+
+/**
+ * Collects all metrics data from metricsToCollect collection.
+ *
+ * @return all metrics in the metricsToCollect snapshot
+ */
+std::vector<prometheus_client::MetricFamily> PrometheusCollector::Collect() const
+{
+  this->collection_lock_.lock();
+  if (metrics_to_collect_->empty())
+  {
+    this->collection_lock_.unlock();
+    return {};
+  }
+  this->collection_lock_.unlock();
+
+  std::vector<prometheus_client::MetricFamily> result;
+
+  // copy the intermediate collection, and then clear it
+  std::vector<metric_sdk::Record> copied_data;
+
+  this->collection_lock_.lock();
+  copied_data = std::vector<metric_sdk::Record>(*metrics_to_collect_);
+  metrics_to_collect_->clear();
+  this->collection_lock_.unlock();
+
+  result = PrometheusExporterUtils::TranslateToPrometheus(copied_data);
+  return result;
+}
+
+/**
+ * This function is called by export() function and add the collection of
+ * records to the metricsToCollect collection
+ *
+ * @param records a collection of records to add to the metricsToCollect collection
+ */
+void PrometheusCollector::AddMetricData(const std::vector<sdk::metrics::Record> &records)
+{
+  if (records.empty())
+  {
+    return;
+  }
+
+  collection_lock_.lock();
+  if (metrics_to_collect_->size() + records.size() <= max_collection_size_)
+  {
+    /**
+     *  ValidAggregator is a lambda that checks a Record to see if its
+     *  Aggregator is a valid nostd::shared_ptr and not a nullptr.
+     */
+    auto ValidAggregator = [](sdk::metrics::Record record) {
+      auto aggregator_variant = record.GetAggregator();
+      if (nostd::holds_alternative<std::shared_ptr<metric_sdk::Aggregator<int>>>(
+              aggregator_variant))
+      {
+        auto aggregator =
+            nostd::get<std::shared_ptr<metric_sdk::Aggregator<int>>>(aggregator_variant);
+        if (!aggregator)
+        {
+          return false;
+        }
+      }
+      else if (nostd::holds_alternative<std::shared_ptr<metric_sdk::Aggregator<short>>>(
+                   aggregator_variant))
+      {
+        auto aggregator =
+            nostd::get<std::shared_ptr<metric_sdk::Aggregator<short>>>(aggregator_variant);
+        if (!aggregator)
+        {
+          return false;
+        }
+      }
+      else if (nostd::holds_alternative<std::shared_ptr<metric_sdk::Aggregator<float>>>(
+                   aggregator_variant))
+      {
+        auto aggregator =
+            nostd::get<std::shared_ptr<metric_sdk::Aggregator<float>>>(aggregator_variant);
+        if (!aggregator)
+        {
+          return false;
+        }
+      }
+      else if (nostd::holds_alternative<std::shared_ptr<metric_sdk::Aggregator<double>>>(
+                   aggregator_variant))
+      {
+        auto aggregator =
+            nostd::get<std::shared_ptr<metric_sdk::Aggregator<double>>>(aggregator_variant);
+        if (!aggregator)
+        {
+          return false;
+        }
+      }
+
+      return true;
+    };
+
+    for (auto &r : records)
+    {
+      if (ValidAggregator(r))
+      {
+        metrics_to_collect_->emplace_back(r);
+      }
+      // Drop the record and write to std::cout
+      else
+      {
+        // Cannot call non const functions on const Record r
+        sdk::metrics::Record c = r;
+        std::cout << "Dropped Record containing invalid aggregator with name: " + c.GetName()
+                  << std::endl;
+      }
+    }
+  }
+  collection_lock_.unlock();
+}
+
+/**
+ * Get the current collection in the collector.
+ *
+ * @return the current metrics_to_collect collection
+ */
+std::vector<sdk::metrics::Record> PrometheusCollector::GetCollection()
+{
+  return *metrics_to_collect_;
+}
+
+/**
+ * Gets the maximum size of the collection.
+ *
+ * @return max collection size
+ */
+int PrometheusCollector::GetMaxCollectionSize() const
+{
+  return max_collection_size_;
+}
+
+}  // namespace prometheus
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE

exporters/prometheus/test/CMakeLists.txt

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