moved Mohamed Bassem's Prometheus plugin into the LogDevice source tree.

.gitmodules

@@ -14,3 +14,6 @@
 [submodule "logdevice/external/fbthrift"]
 	path = logdevice/external/fbthrift
 	url = https://github.com/facebook/fbthrift/
+[submodule "logdevice/external/prometheus-cpp"]
+	path = logdevice/external/prometheus-cpp
+	url = https://github.com/jupp0r/prometheus-cpp/

logdevice/CMake/build-config.cmake

@@ -27,6 +27,5 @@ set(LOGDEVICE_PYTHON_CLIENT_DIR "${LOGDEVICE_DIR}/clients/python")
 set(CMAKE_ARCHIVE_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/lib)
 set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
-set(CMAKE_RUNTIME_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/bin)
 set(UNIT_TEST_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/test)
 set(LOGDEVICE_PY_OUT ${CMAKE_BINARY_DIR}/python-out)

logdevice/CMakeLists.txt

@@ -49,6 +49,8 @@ include(build-config)
 
 option(BUILD_TESTS "If enabled, compile the tests." ON)
 option(BUILD_SUBMODULES "Build using Git submodules, to fulfill dependencies" ON)
+option(BUILD_PLUGINS "If enabled, build standard plugins." ON)
+
 if(${BUILD_SUBMODULES})
   message("Building with submodules enabled")
   include(build-fmt)
@@ -226,3 +228,7 @@ endif()
 add_subdirectory(examples)
 add_subdirectory(clients/python)
 add_subdirectory(ops)
+
+if (${BUILD_PLUGINS})
+  add_subdirectory(plugins/prometheus)
+endif()

logdevice/plugins/prometheus/CMakeLists.txt

@@ -0,0 +1,14 @@
+# Copyright (c) 2017-present, Facebook, Inc. and its affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+list(APPEND CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+list(APPEND CMAKE_PREFIX_PATH "${CMAKE_CURRENT_SOURCE_DIR}/cmake")
+
+set(CMAKE_THREAD_PREFER_PTHREAD ON)
+
+include(build-prometheus-cpp)
+
+add_subdirectory(src)

logdevice/plugins/prometheus/cmake/build-prometheus-cpp.cmake

@@ -0,0 +1,40 @@
+# Copyright (c) 2017-present, Facebook, Inc. and its affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+set(PROMETHEUS_ROOT_DIR ${LOGDEVICE_DIR}/external/prometheus-cpp)
+
+include(ExternalProject)
+
+ExternalProject_Add(prometheus
+    SOURCE_DIR "${PROMETHEUS_ROOT_DIR}"
+    DOWNLOAD_COMMAND ""
+    CMAKE_ARGS
+        -DBUILD_SHARED_LIBS=OFF
+        -DENABLE_TESTING=OFF
+        -DENABLE_PUSH=OFF
+        -DCMAKE_POSITION_INDEPENDENT_CODE=ON
+        -DCMAKE_BUILD_TYPE=${CMAKE_BUILD_TYPE}
+        -DCMAKE_PREFIX_PATH=${LOGDEVICE_STAGING_DIR}/usr/local	
+    INSTALL_COMMAND make install DESTDIR=${LOGDEVICE_STAGING_DIR}
+    )
+
+ExternalProject_Get_Property(prometheus SOURCE_DIR)
+ExternalProject_Get_Property(prometheus BINARY_DIR)
+
+set(PROMETHEUS_LIBRARIES
+    ${LOGDEVICE_STAGING_DIR}/usr/local/lib/libprometheus-cpp-core.a
+    ${LOGDEVICE_STAGING_DIR}/usr/local/lib/libprometheus-cpp-pull.a)
+
+set(PROMETHEUS_INCLUDE_DIR ${LOGDEVICE_STAGING_DIR}/usr/local/include)
+
+message(STATUS "Prometheus Library: ${PROMETHEUS_LIBRARIES}")
+message(STATUS "Prometheus Includes: ${PROMETHEUS_INCLUDE_DIR}")
+
+mark_as_advanced(
+  PROMETHEUS_ROOT_DIR
+  PROMETHEUS_LIBRARIES
+  PROMETHEUS_INCLUDE_DIR
+)

logdevice/plugins/prometheus/src/CMakeLists.txt

@@ -0,0 +1,80 @@
+# Copyright (c) 2017-present, Facebook, Inc. and its affiliates.
+# All rights reserved.
+#
+# This source code is licensed under the BSD-style license found in the
+# LICENSE file in the root directory of this source tree.
+
+# The plugin's main shared library
+add_library(ldprometheus
+    SHARED
+    PrometheusPublisherFactory
+    PrometheusStatsPublisher
+    PrometheusSettings
+    main
+)
+
+add_dependencies(ldprometheus prometheus folly)
+
+target_include_directories(
+    ldprometheus
+    PUBLIC
+        ${LOGDEVICE_INCLUDE_DIRS}
+        ${PROMETHEUS_INCLUDE_DIR}
+)
+
+# Build our shared library with -fPIC
+set_target_properties(
+  ldprometheus
+  PROPERTIES
+  POSITION_INDEPENDENT_CODE True
+)
+
+# Link the prometheus library statically
+target_link_libraries(
+    ldprometheus
+    "-Wl,--whole-archive"
+    ${PROMETHEUS_LIBRARIES}
+    "-Wl,--no-whole-archive"
+)
+
+
+# Building the tests
+if(${BUILD_TESTS})
+  add_executable(prometheus_test tests/PublisherTest.cpp)
+  add_dependencies(prometheus_test ldprometheus)
+  target_include_directories(
+    prometheus_test
+    PUBLIC
+    ${GTEST_INCLUDE_DIRS})
+  target_link_libraries(
+    prometheus_test
+    ldprometheus
+    common
+    logdevice_server  
+    ${GTEST_LIBRARY}
+    ${PROMETHEUS_LIBRARIES}
+    ${LOGDEVICE_EXTERNAL_DEPS}
+    glog
+    Threads::Threads)
+
+  if (HAVE_CMAKE_GTEST)
+    gtest_discover_tests(prometheus_test
+      WORKING_DIRECTORY ${CMAKE_BINARY_DIR})
+  else()
+    add_test(
+      NAME PrometheusTest
+      COMMAND ${UNIT_TEST_OUTPUT_DIRECTORY}/prometheus_test
+      WORKING_DIRECTORY ${CMAKE_BINARY_DIR})
+  endif()
+
+  add_test(NAME prometheus_test COMMAND prometheus_test)
+
+  set_target_properties(prometheus_test
+    PROPERTIES
+    RUNTIME_OUTPUT_DIRECTORY ${UNIT_TEST_OUTPUT_DIRECTORY})
+
+  target_compile_definitions(prometheus_test
+    PRIVATE
+    GTEST_USE_OWN_TR1_TUPLE=0
+  )
+endif(${BUILD_TESTS})

logdevice/plugins/prometheus/src/PrometheusPublisherFactory.h

@@ -0,0 +1,58 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc. and its affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @author Mohamed Bassem 
+ */
+
+#include <logdevice/common/plugin/StatsPublisherFactory.h>
+#include <logdevice/common/settings/Settings.h>
+#include <logdevice/common/settings/SettingsUpdater.h>
+#include <logdevice/common/settings/UpdateableSettings.h>
+
+#include "PrometheusSettings.h"
+#include "PrometheusStatsPublisher.h"
+
+namespace facebook { namespace logdevice {
+
+class PrometheusStatsPublisherFactory : public StatsPublisherFactory {
+ public:
+  virtual ~PrometheusStatsPublisherFactory() = default;
+
+  PluginType type() const override {
+    return PluginType::STATS_PUBLISHER_FACTORY;
+  }
+
+  std::unique_ptr<StatsPublisher> operator()(UpdateableSettings<Settings>,
+                                             int num_db_shards) override {
+    if (prometheus_settings_->prometheus_listen_addr.empty()) {
+      ld_error("Prometheus was used as the stats publisher, but the listen "
+               "address is not set. Will not load the plugin.");
+      return nullptr;
+    }
+    return std::make_unique<PrometheusStatsPublisher>(
+        prometheus_settings_->prometheus_listen_addr);
+  }
+
+  std::string identifier() const override {
+    return "logdevice-prometheus";
+  }
+
+  std::string displayName() const override {
+    return "Logdevice Prometheus";
+  }
+
+  virtual void addOptions(SettingsUpdater* updater) override {
+    updater->registerSettings(prometheus_settings_);
+  }
+
+ private:
+  UpdateableSettings<PrometheusSettings> prometheus_settings_;
+};
+
+}} // namespace facebook::logdevice

logdevice/plugins/prometheus/src/PrometheusSettings.h

@@ -0,0 +1,41 @@
+/**
+ * Copyright (c) 2017-present, Facebook, Inc. and its affiliates.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+/**
+ * @author Mohamed Bassem 
+ */
+
+#include <logdevice/common/settings/UpdateableSettings.h>
+
+namespace facebook { namespace logdevice {
+
+class PrometheusSettings : public SettingsBundle {
+ public:
+  virtual const char* getName() const override {
+    return "Prometheus";
+  }
+
+  virtual void defineSettings(SettingEasyInit& init) {
+    using namespace SettingFlag;
+
+    // TODO add support for push model for clients
+    init("prometheus-listen-addr",
+         &prometheus_listen_addr,
+         "",
+         nullptr,
+         "The address that the prometheus exposer will listen on",
+         SERVER | CLIENT | REQUIRES_RESTART,
+         SettingsCategory::Monitoring);
+  }
+
+  virtual ~PrometheusSettings() override {}
+
+  std::string prometheus_listen_addr;
+};
+
+}} // namespace facebook::logdevice