Add Prometheus Exporter: Step 1

.gitmodules

@@ -0,0 +1,3 @@
+[submodule "third_party/prometheus-cpp"]
+	path = third_party/prometheus-cpp
+	url = https://github.com/jupp0r/prometheus-cpp.git

WORKSPACE

@@ -88,3 +88,16 @@ http_archive(
         "https://github.com/nlohmann/json/releases/download/v3.6.1/include.zip",
     ],
 )
+
+# 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()

ci/Dockerfile

@@ -8,10 +8,12 @@ ADD install_gcc48.sh /setup-ci
 ADD install_bazelisk.sh /setup-ci
 ADD install_protobuf.sh /setup-ci
 ADD install_format_tools.sh /setup-ci
+ADD install_prometheus_client.sh /setup-ci
 
 RUN /setup-ci/setup_ci_environment.sh \
   && /setup-ci/setup_cmake.sh \
   && /setup-ci/install_gcc48.sh \
   && /setup-ci/install_bazelisk.sh \
   && /setup-ci/install_protobuf.sh \
-  && /setup-ci/install_format_tools.sh
+  && /setup-ci/install_format_tools.sh \
+  && /setup-ci/install_prometheus_client.sh

ci/install_prometheus_client.sh

@@ -0,0 +1,10 @@
+#!/bin/bash
+
+git clone https://github.com/jupp0r/prometheus-cpp.git
+cd prometheus-cpp
+git checkout v0.9.0
+git submodule init
+git submodule update
+mkdir _build && cd _build
+cmake .. -DBUILD_SHARED_LIBS=ON
+make && make install

ci/ports/prometheus-cpp/CONTROL

@@ -0,0 +1,20 @@
+Source: prometheus-cpp
+Version: 0.9.0
+Description: Prometheus Client Library for Modern C++
+Default-Features: compression, pull
+
+Feature: compression
+Build-Depends: zlib
+Description: Enable zlib compression
+
+Feature: tests
+Build-Depends: gtest
+Description: Additional testing support
+
+Feature: pull
+Build-Depends: civetweb
+Description: Support for regular pull mode
+
+Feature: push
+Build-Depends: curl
+Description: Support push gateway

ci/ports/prometheus-cpp/portfile.cmake

@@ -0,0 +1,43 @@
+include(vcpkg_common_functions)
+
+vcpkg_check_linkage(ONLY_STATIC_LIBRARY)
+
+vcpkg_from_github(
+        OUT_SOURCE_PATH SOURCE_PATH
+        REPO jupp0r/prometheus-cpp
+        REF v0.9.0
+        SHA512 d9d5fbbd8c8aad5dd6a5e872275324d689a0c57199e4158d74e13ea62b286fa71dee01bb4197b906b79792bf1ca4e67a46b5c04621d7070241ac32876f6de891
+        HEAD_REF master
+)
+
+macro(feature FEATURENAME OPTIONNAME)
+    if ("${FEATURENAME}" IN_LIST FEATURES)
+        list(APPEND FEATURE_OPTIONS -D${OPTIONNAME}=TRUE)
+    else ()
+        list(APPEND FEATURE_OPTIONS -D${OPTIONNAME}=FALSE)
+    endif ()
+endmacro()
+
+feature(compression ENABLE_COMPRESSION)
+feature(pull ENABLE_PULL)
+feature(push ENABLE_PUSH)
+feature(tests ENABLE_TESTING)
+
+vcpkg_configure_cmake(
+        SOURCE_PATH ${SOURCE_PATH}
+        PREFER_NINJA
+        OPTIONS
+        -DUSE_THIRDPARTY_LIBRARIES=OFF # use vcpkg packages
+        ${FEATURE_OPTIONS}
+)
+
+vcpkg_install_cmake()
+
+vcpkg_copy_pdbs()
+
+vcpkg_fixup_cmake_targets(CONFIG_PATH lib/cmake/prometheus-cpp)
+
+file(REMOVE_RECURSE ${CURRENT_PACKAGES_DIR}/debug/include)
+
+# Handle copyright
+configure_file(${SOURCE_PATH}/LICENSE ${CURRENT_PACKAGES_DIR}/share/prometheus-cpp/copyright COPYONLY)

ci/setup_cmake.sh

@@ -5,7 +5,8 @@ set -e
 apt-get install --no-install-recommends --no-install-suggests -y \
                 cmake \
                 libbenchmark-dev \
-                libgtest-dev
+                libgtest-dev \
+                libcurl4-openssl-dev
 
 # Follows these instructions for setting up gtest
 # https://www.eriksmistad.no/getting-started-with-google-test-on-ubuntu/

ci/setup_windows_ci_environment.ps1

@@ -12,4 +12,6 @@ $VCPKG_DIR=(Get-Item -Path ".\").FullName
 ./vcpkg install --overlay-ports="$PSScriptRoot\ports" benchmark:x64-windows
 
 ./vcpkg install gtest:x64-windows
+
+./vcpkg install --overlay-ports="$PSScriptRoot\ports" prometheus-cpp:x64-windows
 Pop-Location

exporters/CMakeLists.txt

@@ -2,3 +2,4 @@ if(WITH_OTPROTOCOL)
   add_subdirectory(otlp)
 endif()
 add_subdirectory(ostream)
+add_subdirectory(prometheus)

exporters/prometheus/BUILD

@@ -0,0 +1,42 @@
+# 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_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_utils_test",
+    srcs = [
+        "test/prometheus_exporter_utils_test.cc",
+    ],
+    deps = [
+        ":prometheus_utils",
+        "@com_google_googletest//:gtest_main",
+    ],
+)

exporters/prometheus/CMakeLists.txt

@@ -0,0 +1,22 @@
+# 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_utils.cc)
+
+if(BUILD_TESTING)
+  add_subdirectory(test)
+endif()

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

@@ -0,0 +1,183 @@
+/*
+ * 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);
+
+  /**
+   * Set value to metric family for different aggregator
+   */
+  template <typename T>
+  static void SetMetricFamilyByAggregator(std::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,
+                      bool do_quantile,
+                      std::vector<double> quantile_points);
+
+  /**
+   * 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(std::shared_ptr<metric_sdk::Aggregator<T>> aggregator,
+                                           const std::vector<double> &quantile_points);
+
+  /**
+   * 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,
+                       bool do_quantile,
+                       const std::vector<double> &quantile_points);
+};
+}  // namespace prometheus
+}  // namespace exporter
+OPENTELEMETRY_END_NAMESPACE