Add Prometheus Exporter - Utils header and build config for bazel and CMake

WORKSPACE

@@ -16,6 +16,30 @@ workspace(name = "io_opentelemetry_cpp")
 
 load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive")
 
+# Load gRPC dependency
+# Note that this dependency needs to be loaded first due to
+# https://github.com/bazelbuild/bazel/issues/6664
+http_archive(
+    name = "com_github_grpc_grpc",
+    strip_prefix = "grpc-1.28.0",
+    urls = [
+        "https://github.com/grpc/grpc/archive/v1.28.0.tar.gz",
+    ],
+)
+
+load("@com_github_grpc_grpc//bazel:grpc_deps.bzl", "grpc_deps")
+
+grpc_deps()
+
+# Load extra gRPC dependencies due to https://github.com/grpc/grpc/issues/20511
+load("@com_github_grpc_grpc//bazel:grpc_extra_deps.bzl", "grpc_extra_deps")
+
+grpc_extra_deps()
+
+load("@upb//bazel:repository_defs.bzl", "bazel_version_repository")
+
+bazel_version_repository(name = "upb_bazel_version")
+
 # Uses older protobuf version because of
 # https://github.com/protocolbuffers/protobuf/issues/7179
 http_archive(
@@ -54,3 +78,16 @@ http_archive(
     strip_prefix = "benchmark-1.5.0",
     urls = ["https://github.com/google/benchmark/archive/v1.5.0.tar.gz"],
 )
+
+# C++ Prometheus Client library.
+load("@bazel_tools//tools/build_defs/repo:http.bzl", "http_archive", "http_file")
+
+http_archive(
+    name = "com_github_jupp0r_prometheus_cpp",
+    strip_prefix = "prometheus-cpp-master",
+    urls = ["https://github.com/jupp0r/prometheus-cpp/archive/master.zip"],
+)
+
+load("@com_github_jupp0r_prometheus_cpp//bazel:repositories.bzl", "prometheus_cpp_repositories")
+
+prometheus_cpp_repositories()

exporters/prometheus/BUILD

@@ -0,0 +1,104 @@
+# 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.
+
+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 = [
+        "//api",
+        "//sdk:headers",
+        "@com_github_jupp0r_prometheus_cpp//core",
+        "@com_github_jupp0r_prometheus_cpp//pull",
+    ],
+)
+
+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 = [
+        "src/prometheus_exporter_utils.cc",
+    ],
+    hdrs = [
+        "include/opentelemetry/exporters/prometheus/prometheus_exporter_utils.h",
+    ],
+    strip_include_prefix = "include",
+    deps = [
+        "//api",
+        "//sdk:headers",
+        "@com_github_jupp0r_prometheus_cpp//core",
+    ],
+)
+
+cc_test(
+    name = "prometheus_exporter_test",
+    srcs = [
+        "test/prometheus_exporter_test.cc",
+    ],
+    deps = [
+        ":prometheus_collector",
+        ":prometheus_exporter",
+        "@com_github_jupp0r_prometheus_cpp//core",
+        "@com_github_jupp0r_prometheus_cpp//pull",
+        "@com_google_googletest//:gtest_main",
+    ],
+)
+
+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 = [
+        "test/prometheus_exporter_utils_test.cc",
+    ],
+    deps = [
+        ":prometheus_utils",
+        "@com_google_googletest//:gtest_main",
+    ],
+)

exporters/prometheus/CMakeLists.txt

@@ -0,0 +1,24 @@
+# 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.
+
+include_directories(include)
+
+find_package(prometheus-cpp CONFIG REQUIRED)
+add_library(
+        prometheus_exporter src/prometheus_exporter.cc src/prometheus_collector.cc
+        src/prometheus_exporter_utils.cc)
+
+if (BUILD_TESTING)
+    add_subdirectory(test)
+endif ()

exporters/prometheus/include/opentelemetry/exporters/prometheus/prometheus_exporter_utils.h

@@ -0,0 +1,189 @@
+/*
+ * 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 <string>
+#include <vector>
+
+#include "opentelemetry/sdk/metrics/record.h"
+#include "prometheus/metric_family.h"
+
+namespace prometheus_client = ::prometheus;
+namespace metric_sdk        = opentelemetry::sdk::metrics;
+
+OPENTELEMETRY_BEGIN_NAMESPACE
+namespace exporter
+{
+namespace prometheus
+{
+/**
+ * The Prometheus Utils contains utility functions for Prometheus Exporter
+ */
+class PrometheusExporterUtils
+{
+public:
+  /**
+   * Helper function to convert OpenTelemetry metrics data collection
+   * to Prometheus metrics data collection
+   *
+   * @param records a collection of metrics in OpenTelemetry
+   * @return a collection of translated metrics that is acceptable by Prometheus
+   */
+  static std::vector<prometheus_client::MetricFamily> TranslateToPrometheus(
+      std::vector<metric_sdk::Record> &records);
+
+private:
+  /**
+   * Set value to metric family according to record
+   */
+  static void SetMetricFamily(metric_sdk::Record &record,
+                              prometheus_client::MetricFamily *metric_family);
+
+  /**
+   * Sanitize the given metric name or label according to Prometheus rule.
+   *
+   * This function is needed because names in OpenTelemetry can contain
+   * alphanumeric characters, '_', '.', and '-', whereas in Prometheus the
+   * name should only contain alphanumeric characters and '_'.
+   */
+  static std::string SanitizeNames(std::string name);
+
+  /**
+   * Determine whether the input name is a valid OTel name or not
+   *
+   * From the spec:
+   * 1. They are non-empty strings
+   * 2. They are case-insensitive
+   * 3. The first character must be non-numeric, non-space, non-punctuation
+   * 4. Subsequent characters must belong to the alphanumeric characters, '_', '.', and '-'.
+   */
+  static bool IsValidName(const std::string &name);
+
+  /**
+   * Set value to metric family for different aggregator
+   */
+  template <typename T>
+  static void SetMetricFamilyByAggregator(nostd::shared_ptr<metric_sdk::Aggregator<T>> aggregator,
+                                          std::string labels_str,
+                                          prometheus_client::MetricFamily *metric_family);
+
+  /**
+   * Translate the OTel metric type to Prometheus metric type
+   */
+  static prometheus_client::MetricType TranslateType(metric_sdk::AggregatorKind kind);
+
+  /**
+   * Set metric data for:
+   * Counter => Prometheus Counter
+   * Gauge => Prometheus Gauge
+   */
+  template <typename T>
+  static void SetData(std::vector<T> values,
+                      const std::string &labels,
+                      prometheus_client::MetricType type,
+                      std::chrono::nanoseconds time,
+                      prometheus_client::MetricFamily *metric_family);
+
+  /**
+   * Set metric data for:
+   * Histogram => Prometheus Histogram
+   */
+  template <typename T>
+  static void SetData(std::vector<T> values,
+                      const std::vector<double> &boundaries,
+                      const std::vector<int> &counts,
+                      const std::string &labels,
+                      std::chrono::nanoseconds time,
+                      prometheus_client::MetricFamily *metric_family);
+
+  /**
+   * Set metric data for:
+   * MinMaxSumCount => Prometheus Gauge
+   * Use Average (sum / count) as the gauge metric
+   */
+  static void SetData(double value,
+                      const std::string &labels,
+                      std::chrono::nanoseconds time,
+                      prometheus_client::MetricFamily *metric_family);
+
+  /**
+   * Set metric data for:
+   * Exact => Prometheus Summary
+   * Sketch => Prometheus Summary
+   */
+  template <typename T>
+  static void SetData(std::vector<T> values,
+                      metric_sdk::AggregatorKind kind,
+                      const std::vector<T> &quantiles,
+                      const std::string &labels,
+                      std::chrono::nanoseconds time,
+                      prometheus_client::MetricFamily *metric_family);
+
+  /**
+   * Set time and labels to metric data
+   */
+  static void SetMetricBasic(prometheus_client::ClientMetric &metric,
+                             std::chrono::nanoseconds time,
+                             const std::string &labels);
+
+  /**
+   * Parse a string of labels (key:value) into a vector of pairs
+   * {,}
+   * {l1:v1,l2:v2,...,}
+   */
+  static std::vector<std::pair<std::string, std::string>> ParseLabel(std::string labels);
+
+  /**
+   * Build a quantiles vector from aggregator
+   */
+  template <typename T>
+  static std::vector<T> GetQuantilesVector(nostd::shared_ptr<metric_sdk::Aggregator<T>> aggregator);
+
+  /**
+   * Handle Counter and Gauge.
+   */
+  template <typename T>
+  static void SetValue(std::vector<T> values,
+                       prometheus_client::MetricType type,
+                       prometheus_client::ClientMetric *metric);
+
+  /**
+   * Handle Gauge from MinMaxSumCount
+   */
+  static void SetValue(double value, prometheus_client::ClientMetric *metric);
+
+  /**
+   * Handle Histogram
+   */
+  template <typename T>
+  static void SetValue(std::vector<T> values,
+                       std::vector<double> boundaries,
+                       std::vector<int> counts,
+                       prometheus_client::ClientMetric *metric);
+
+  /**
+   * Handle Exact and Sketch
+   */
+  template <typename T>
+  static void SetValue(std::vector<T> values,
+                       metric_sdk::AggregatorKind kind,
+                       std::vector<T> quantiles,
+                       prometheus_client::ClientMetric *metric);
+};
+}  // namespace prometheus
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE