[Tarantool-patches] [PATCH] build: link bundled libcurl with c-ares

[Serge Petrenko <sergepetrenko@tarantool.org>]

libcurl has a built-in threaded resolver used for asynchronous DNS
requests, however, when DNS server is slow to respond, the request still
hangs tarantool until it is finished. The reason is that curl calls
thread_join on the resolving thread internally upon timeout, making the
calling thread hang until resolution has ended.
Use c-ares as an asynchronous resolver instead to eliminate the problem.

Closes #4591
---
https://github.com/tarantool/tarantool/issues/4591
https://github.com/tarantool/tarantool/tree/sp/gh-4591-link-curl-with-c-ares-full-ci

 .gitmodules              |  3 ++
 CMakeLists.txt           |  6 ++++
 cmake/BuildAres.cmake    | 67 ++++++++++++++++++++++++++++++++++++++++
 cmake/BuildLibCURL.cmake | 31 +++++++++++++++++--
 third_party/c-ares       |  1 +
 5 files changed, 106 insertions(+), 2 deletions(-)
 create mode 100644 cmake/BuildAres.cmake
 create mode 160000 third_party/c-ares

diff --git a/.gitmodules b/.gitmodules
index 76303e0c5..d45e9ce8b 100644
--- a/.gitmodules
+++ b/.gitmodules
@@ -40,3 +40,6 @@
 [submodule "third_party/curl"]
 	path = third_party/curl
 	url = https://github.com/tarantool/curl.git
+[submodule "third_party/c-ares"]
+	path = third_party/c-ares
+	url = https://github.com/tarantool/c-ares.git
diff --git a/CMakeLists.txt b/CMakeLists.txt
index 7d6c0846e..dca060857 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -339,7 +339,13 @@ endif()
 # Curl
 #
 option(ENABLE_BUNDLED_LIBCURL "Enable building of the bundled libcurl" ON)
+option(BUNDLED_LIBCURL_USE_ARES "Build curl with bundled c-ares"
+       ${ENABLE_BUNDLED_LIBCURL})
 if (ENABLE_BUNDLED_LIBCURL)
+    if(BUNDLED_LIBCURL_USE_ARES)
+        include(BuildAres)
+        ares_build()
+    endif()
     include(BuildLibCURL)
     curl_build()
     add_dependencies(build_bundled_libs bundled-libcurl)
diff --git a/cmake/BuildAres.cmake b/cmake/BuildAres.cmake
new file mode 100644
index 000000000..ea4cfdd9d
--- /dev/null
+++ b/cmake/BuildAres.cmake
@@ -0,0 +1,67 @@
+# A macro to build the bundled libcares
+macro(ares_build)
+    set(ARES_SOURCE_DIR ${PROJECT_SOURCE_DIR}/third_party/c-ares)
+    set(ARES_BINARY_DIR ${PROJECT_BINARY_DIR}/build/ares/work)
+    set(ARES_INSTALL_DIR ${PROJECT_BINARY_DIR}/build/ares/dest)
+
+    # See BuildLibCURL.cmake for details.
+    set(ARES_CPPFLAGS "")
+    set(ARES_CFLAGS "")
+    set(ARES_CXXFLAGS "")
+    if (TARGET_OS_DARWIN AND NOT "${CMAKE_OSX_SYSROOT}" STREQUAL "")
+        set(ARES_CPPFLAGS "${ARES_CPPFLAGS} ${CMAKE_C_SYSROOT_FLAG} ${CMAKE_OSX_SYSROOT}")
+        set(ARES_CFLAGS "${ARES_CFLAGS} ${CMAKE_C_SYSROOT_FLAG} ${CMAKE_OSX_SYSROOT}")
+        set(ARES_CXXFLAGS "${ARES_CXXFLAGS} ${CMAKE_CXX_SYSROOT_FLAG} ${CMAKE_OSX_SYSROOT}")
+    endif()
+
+    include(ExternalProject)
+    ExternalProject_Add(
+        bundled-ares-project
+        SOURCE_DIR ${ARES_SOURCE_DIR}
+        PREFIX ${ARES_INSTALL_DIR}
+        DOWNLOAD_DIR ${ARES_BINARY_DIR}
+        TMP_DIR ${ARES_BINARY_DIR}/tmp
+        STAMP_DIR ${ARES_BINARY_DIR}/stamp
+        BINARY_DIR ${ARES_BINARY_DIR}
+        CONFIGURE_COMMAND
+            cd <SOURCE_DIR> && ./buildconf &&
+            cd <BINARY_DIR> && <SOURCE_DIR>/configure
+                # Pass the same toolchain as is used to build
+                # tarantool itself, because they can be
+                # incompatible.
+                CC=${CMAKE_C_COMPILER}
+                CXX=${CMAKE_CXX_COMPILER}
+                LD=${CMAKE_LINKER}
+                AR=${CMAKE_AR}
+                RANLIB=${CMAKE_RANLIB}
+                NM=${CMAKE_NM}
+                STRIP=${CMAKE_STRIP}
+
+                CFLAGS=${ARES_CFLAGS}
+                CPPFLAGS=${ARES_CPPFLAGS}
+                CXXFLAGS=${ARES_CXXFLAGS}
+                # Pass empty LDFLAGS to discard using of
+                # corresponding environment variable.
+                # It is possible that a linker flag assumes that
+                # some compilation flag is set. We don't pass
+                # CFLAGS from environment, so we should not do it
+                # for LDFLAGS too.
+                LDFLAGS=
+
+                --prefix=<INSTALL_DIR>
+                --enable-static
+
+        BUILD_COMMAND cd <BINARY_DIR> && $(MAKE)
+        INSTALL_COMMAND cd <BINARY_DIR> && $(MAKE) install)
+
+    add_library(bundled-ares STATIC IMPORTED GLOBAL)
+    set_target_properties(bundled-ares PROPERTIES IMPORTED_LOCATION
+        ${ARES_INSTALL_DIR}/lib/libcares.a)
+    add_dependencies(bundled-ares bundled-ares-project)
+
+    unset(ARES_CPPFLAGS)
+    unset(ARES_CFLAGS)
+    unset(ARES_CXXFLAGS)
+    unset(ARES_BINARY_DIR)
+    unset(ARES_SOURCE_DIR)
+endmacro(ares_build)
diff --git a/cmake/BuildLibCURL.cmake b/cmake/BuildLibCURL.cmake
index 6d40ab045..756297878 100644
--- a/cmake/BuildLibCURL.cmake
+++ b/cmake/BuildLibCURL.cmake
@@ -19,6 +19,21 @@ macro(curl_build)
     get_filename_component(FOUND_OPENSSL_ROOT_DIR ${OPENSSL_INCLUDE_DIR} DIRECTORY)
     set(LIBCURL_OPENSSL_OPT "--with-ssl=${FOUND_OPENSSL_ROOT_DIR}")
 
+    # Use either c-ares bundled with tarantool or
+    # libcurl-default threaded resolver.
+    if(BUNDLED_LIBCURL_USE_ARES)
+        set(ASYN_DNS_USED "ares")
+        set(ASYN_DNS_UNUSED "threaded-resolver")
+        set(ASYN_DNS_PATH "=${ARES_INSTALL_DIR}")
+    else()
+        set(ASYN_DNS_USED "threaded-resolver")
+        set(ASYN_DNS_UNUSED "ares")
+        set(ASYN_DNS_PATH "")
+    endif()
+
+    set(ENABLED_DNS_OPT "--enable-${ASYN_DNS_USED}${ASYN_DNS_PATH}")
+    set(DISABLED_DNS_OPT "--disable-${ASYN_DSN_UNUSED}")
+
     # Pass -isysroot=<SDK_PATH> option on Mac OS to a preprocessor
     # and a C compiler to find header files installed with an SDK.
     #
@@ -100,17 +115,17 @@ macro(curl_build)
                 --without-zsh-functions-dir
                 --without-fish-functions-dir
 
+                ${ENABLED_DNS_OPT}
                 --enable-http
                 --enable-proxy
                 --enable-ipv6
-                --enable-threaded-resolver
                 --enable-unix-sockets
                 --enable-cookies
                 --enable-http-auth
                 --enable-mime
                 --enable-dateparse
 
-                --disable-ares
+                ${DISABLED_DNS_OPT}
                 --disable-ftp
                 --disable-file
                 --disable-ldap
@@ -140,14 +155,26 @@ macro(curl_build)
     add_library(bundled-libcurl STATIC IMPORTED GLOBAL)
     set_target_properties(bundled-libcurl PROPERTIES IMPORTED_LOCATION
         ${LIBCURL_INSTALL_DIR}/lib/libcurl.a)
+    if (BUNDLED_LIBCURL_USE_ARES)
+        # Need to build ares first
+        add_dependencies(bundled-libcurl-project bundled-ares)
+    endif()
     add_dependencies(bundled-libcurl bundled-libcurl-project)
 
     set(CURL_INCLUDE_DIRS ${LIBCURL_INSTALL_DIR}/include)
     set(CURL_LIBRARIES bundled-libcurl ${LIBZ_LIBRARY})
+    if (BUNDLED_LIBCURL_USE_ARES)
+        set(CURL_LIBRARIES ${CURL_LIBRARIES} bundled-ares)
+    endif()
     if (TARGET_OS_LINUX OR TARGET_OS_FREEBSD)
         set(CURL_LIBRARIES ${CURL_LIBRARIES} rt)
     endif()
 
+    unset(ASYN_DNS_USED)
+    unset(ASYN_DNS_UNUSED)
+    unset(ASYN_DNS_PATH)
+    unset(ENABLED_DNS_OPT)
+    unset(DISABLED_DNS_OPT)
     unset(LIBCURL_CPPFLAGS)
     unset(LIBCURL_CFLAGS)
     unset(FOUND_OPENSSL_ROOT_DIR)
diff --git a/third_party/c-ares b/third_party/c-ares
new file mode 160000
index 000000000..14e38b154
--- /dev/null
+++ b/third_party/c-ares
@@ -0,0 +1 @@
+Subproject commit 14e38b154c972cd41fed277e6f5c4fc8f0ed8d9f
-- 
2.21.0 (Apple Git-122)