cmake: allow running the tests in parallel like in the Makefile (#102)

Allow running tests in parallel by default by setting the CTEST_PARALLEL_LEVEL
environment variable. The functionality is added using a CMake script in
order to determine options when running the tests (rather than when configuring
CMake) in compatibility with the Makefile (in particular -- the `J` and
`TEST_TMPDIR` environment variables).

Test Plan: run the check target using different generators (ninja, make)
to see the improvement in test runtime.

CMakeLists.txt

@@ -1190,6 +1190,18 @@ if(WITH_TESTS OR WITH_BENCHMARK_TOOLS)
 endif()
 
 if(WITH_TESTS)
+  # c_test - doesn't use gtest
+  # env_test - suspicious use of test::TmpDir
+  # deletefile_test - serial because it generates giant temporary files in
+  #   its various tests. Running its tests in parallel can fill up your /dev/shm
+  # db_bloom_filter_test - serial because excessive space usage by instances
+  #   of DBFilterConstructionReserveMemoryTestWithParam can fill up /dev/shm
+  set(NON_PARALLEL_TEST
+    c_test
+    env_test
+    deletefile_test
+    db_bloom_filter_test
+  )
   set(TESTS
         db/db_basic_test.cc
         env/env_basic_test.cc
@@ -1396,7 +1408,10 @@ if(WITH_TESTS)
       utilities/cassandra/test_utils.cc
   )
   enable_testing()
-  add_custom_target(check COMMAND ${CMAKE_CTEST_COMMAND})
+  add_custom_target(check
+    COMMAND ${CMAKE_COMMAND} -P ${PROJECT_SOURCE_DIR}/cmake/CTestRunner.cmake
+    WORKING_DIRECTORY ${PROJECT_BINARY_DIR}
+    VERBATIM USES_TERMINAL)
   set(TESTUTILLIB testutillib${ARTIFACT_SUFFIX})
   add_library(${TESTUTILLIB} STATIC ${TESTUTIL_SOURCE})
   target_link_libraries(${TESTUTILLIB} ${ROCKSDB_LIB})
@@ -1419,10 +1434,12 @@ if(WITH_TESTS)
         OUTPUT_NAME ${exename}${ARTIFACT_SUFFIX}
       )
       target_link_libraries(${exename}${ARTIFACT_SUFFIX} ${TESTUTILLIB} testharness gtest ${THIRDPARTY_LIBS} ${ROCKSDB_LIB})
-      if(NOT "${exename}" MATCHES "db_sanity_test")
+      if(NOT "${exename}" IN_LIST NON_PARALLEL_TEST)
         gtest_discover_tests(${exename} DISCOVERY_TIMEOUT 120)
-        add_dependencies(check ${exename}${ARTIFACT_SUFFIX})
+      else()
+        add_test(NAME ${exename} COMMAND ${exename}${ARTIFACT_SUFFIX})
       endif()
+      add_dependencies(check ${exename}${ARTIFACT_SUFFIX})
   endforeach(sourcefile ${TESTS})
 
   if(WIN32)

cmake/CTestRunner.cmake

@@ -0,0 +1,58 @@
+# Copyright (C) 2022 Speedb Ltd. All rights reserved.
+#
+# 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.
+
+# Choose the amount of tests to run in parallel if CTEST_PARALLEL_LEVEL wasn't set
+if(NOT DEFINED ENV{CTEST_PARALLEL_LEVEL})
+    # Compatibility with the Makefile: support the `J` environment variable
+    if(DEFINED ENV{J} AND "$ENV{J}" GREATER 0)
+        set(ENV{CTEST_PARALLEL_LEVEL} ${ENV{J}})
+    else()
+        include(ProcessorCount)
+        ProcessorCount(NCPU)
+        if(NOT NCPU EQUAL 0)
+            set(ENV{CTEST_PARALLEL_LEVEL} ${NCPU})
+        endif()
+    endif()
+endif()
+
+if(NOT DEFINED ENV{TEST_TMPDIR} AND "${CMAKE_HOST_SYSTEM_NAME}" STREQUAL "Linux")
+    # Use /dev/shm if the sticky bit is set
+    if(IS_DIRECTORY /dev/shm)
+        execute_process(COMMAND test -k /dev/shm RESULT_VARIABLE status OUTPUT_QUIET ERROR_QUIET)
+        if(status EQUAL 0)
+            set(test_dir /dev/shm)
+        endif()
+    endif()
+    # Fall back to /tmp if exists
+    if(NOT DEFINED test_dir AND IS_DIRECTORY /tmp)
+        set(test_dir /tmp)
+    endif()
+    # Create a temporary directory under the test location that we determined
+    if(DEFINED test_dir)
+        execute_process(
+            COMMAND "mktemp" "-d" "${test_dir}/rocksdb.XXXX"
+            RESULT_VARIABLE status OUTPUT_VARIABLE tmpdir
+            OUTPUT_STRIP_TRAILING_WHITESPACE)
+        if (NOT status EQUAL 0)
+            message(FATAL_ERROR "mkdtemp failed")
+        endif()
+        set(ENV{TEST_TMPDIR} ${tmpdir})
+    endif()
+endif()
+
+if(DEFINED ENV{TEST_TMPDIR})
+    message(STATUS "Running $ENV{CTEST_PARALLEL_LEVEL} tests in parallel in $ENV{TEST_TMPDIR}")
+endif()
+
+# Run all tests, with a timeout of 10 minutes per test and show test output on failure
+execute_process(COMMAND ${CMAKE_CTEST_COMMAND} --output-on-failure --timeout 600)