Integrate libevent with cmake

CMakeLists.txt

@@ -12,12 +12,16 @@ endif()
 
 option(WITH_OTPROTOCOL
        "Whether to include the OpenTelemetry Protocol in the SDK" OFF)
+option(WITH_LIBEVENT
+      "Build SDK with libevent support" ON)
 
 set(WITH_PROTOBUF OFF)
 if(WITH_OTPROTOCOL)
   set(WITH_PROTOBUF ON)
 endif()
 
+set(CMAKE_MODULE_PATH ${CMAKE_MODULE_PATH} "${CMAKE_SOURCE_DIR}/cmake/Modules/")
+
 include(CTest)
 
 find_package(Threads)
@@ -42,6 +46,11 @@ if(WITH_OTPROTOCOL)
   include(third_party/opentelemetry-proto/Protobuf.cmake)
 endif()
 
+if(WITH_LIBEVENT)
+  find_package(Libevent REQUIRED)
+  include_directories(SYSTEM ${LIBEVENT_INCLUDE_DIRS})
+endif()
+
 if(BUILD_TESTING)
   find_package(GTest REQUIRED)
   find_package(benchmark REQUIRED)

ci/Dockerfile

@@ -6,12 +6,14 @@ ADD setup_ci_environment.sh /setup-ci
 ADD setup_cmake.sh /setup-ci
 ADD install_gcc48.sh /setup-ci
 ADD install_bazelisk.sh /setup-ci
+ADD install_libevent.sh /setup-ci
 ADD install_protobuf.sh /setup-ci
 ADD install_format_tools.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_libevent.sh \
   && /setup-ci/install_protobuf.sh \
   && /setup-ci/install_format_tools.sh

ci/install_libevent.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+set -e
+
+apt-get install --no-install-recommends --no-install-suggests -y \
+                libevent-dev
+

cmake/Modules/FindLibevent.cmake

@@ -0,0 +1,48 @@
+# find LibEvent
+# an event notification library (http://libevent.org/)
+#
+# Usage: 
+# LIBEVENT_INCLUDE_DIRS, where to find LibEvent headers
+# LIBEVENT_LIBRARIES, LibEvent libraries
+# Libevent_FOUND, If false, do not try to use libevent
+#
+# Taken from https://github.com/apache/thrift/blob/7edc8faefd391ce11eca3023a35cc54bcb2eb1af/build/cmake/FindLibevent.cmake
+# with modification.
+
+set(LIBEVENT_ROOT CACHE PATH "Root directory of libevent installation")
+set(LibEvent_EXTRA_PREFIXES /usr/local /opt/local "$ENV{HOME}" ${LIBEVENT_ROOT})
+foreach(prefix ${LibEvent_EXTRA_PREFIXES})
+  list(APPEND LibEvent_INCLUDE_PATHS "${prefix}/include")
+  list(APPEND LibEvent_LIBRARIES_PATHS "${prefix}/lib")
+endforeach()
+
+# Looking for "event.h" will find the Platform SDK include dir on windows
+# so we also look for a peer header like evhttp.h to get the right path
+find_path(LIBEVENT_INCLUDE_DIRS evhttp.h event.h PATHS ${LibEvent_INCLUDE_PATHS})
+
+# "lib" prefix is needed on Windows in some cases
+# newer versions of libevent use three libraries
+find_library(LIBEVENT_LIBRARIES NAMES event_core PATHS ${LibEvent_LIBRARIES_PATHS})
+
+if (LIBEVENT_LIBRARIES AND LIBEVENT_INCLUDE_DIRS)
+  set(Libevent_FOUND TRUE)
+  set(LIBEVENT_LIBRARIES ${LIBEVENT_LIBRARIES})
+else ()
+  set(Libevent_FOUND FALSE)
+endif ()
+
+if (Libevent_FOUND)
+  if (NOT Libevent_FIND_QUIETLY)
+    message(STATUS "Found libevent: ${LIBEVENT_LIBRARIES}")
+  endif ()
+else ()
+  if (LibEvent_FIND_REQUIRED)
+    message(FATAL_ERROR "Could NOT find libevent.")
+  endif ()
+  message(STATUS "libevent NOT found.")
+endif ()
+
+mark_as_advanced(
+    LIBEVENT_LIBRARIES
+    LIBEVENT_INCLUDE_DIRS
+  )

sdk/src/CMakeLists.txt

@@ -1,2 +1,3 @@
 add_subdirectory(common)
+add_subdirectory(event)
 add_subdirectory(trace)

sdk/src/event/CMakeLists.txt

@@ -0,0 +1,3 @@
+if(WITH_LIBEVENT)
+  add_subdirectory(libevent)
+endif()

sdk/src/event/libevent/CMakeLists.txt

@@ -0,0 +1,7 @@
+add_library(opentelemetry_event_libevent 
+        dispatcher.cc
+        event.cc
+        event_base.cc
+        file_event.cc
+        timer.cc)
+target_link_libraries(opentelemetry_event_libevent ${LIBEVENT_LIBRARIES})

sdk/test/CMakeLists.txt

@@ -1,2 +1,3 @@
 add_subdirectory(common)
+add_subdirectory(event)
 add_subdirectory(trace)

sdk/test/event/CMakeLists.txt

@@ -0,0 +1,3 @@
+if(WITH_LIBEVENT)
+  add_subdirectory(libevent)
+endif()

sdk/test/event/libevent/CMakeLists.txt

@@ -0,0 +1,6 @@
+foreach(testname dispatcher_test)
+  add_executable(${testname} "${testname}.cc")
+  target_link_libraries(${testname} ${GTEST_BOTH_LIBRARIES}
+                        ${CMAKE_THREAD_LIBS_INIT} opentelemetry_event_libevent)
+  gtest_add_tests(TARGET ${testname} TEST_PREFIX event. TEST_LIST ${testname})
+endforeach()