Fix a bug causing LOG is not created when max_log_file_size is set.

Summary:
Fix a bug causing LOG is not created when max_log_file_size is set.
This bug is reported in issue #174.

Test Plan:
Add TEST(AutoRollLoggerTest, LogFileExistence).
make auto_roll_logger_test
./auto_roll_logger_test

Reviewers: haobo, sdong, ljin, igor, igor2

Reviewed By: igor2

Subscribers: dhruba, leveldb

Differential Revision: https://reviews.facebook.net/D19053

util/auto_roll_logger.cc

@@ -87,6 +87,7 @@ Status CreateLoggerFromOptions(
   env->GetAbsolutePath(dbname, &db_absolute_path);
   std::string fname = InfoLogFileName(dbname, db_absolute_path, db_log_dir);
 
+  env->CreateDirIfMissing(dbname);  // In case it does not exist
   // Currently we only support roll by time-to-roll and log size
   if (options.log_file_time_to_roll > 0 || options.max_log_file_size > 0) {
     AutoRollLogger* result = new AutoRollLogger(
@@ -102,7 +103,6 @@ Status CreateLoggerFromOptions(
     return s;
   } else {
     // Open a log file in the same directory as the db
-    env->CreateDir(dbname);  // In case it does not exist
     env->RenameFile(fname, OldInfoLogFileName(dbname, env->NowMicros(),
                                               db_absolute_path, db_log_dir));
     auto s = env->NewLogger(fname, logger);

util/auto_roll_logger_test.cc

@@ -285,6 +285,18 @@ TEST(AutoRollLoggerTest, InfoLogLevel) {
   inFile.close();
 }
 
+TEST(AutoRollLoggerTest, LogFileExistence) {
+  rocksdb::DB* db;
+  rocksdb::Options options;
+  string deleteCmd = "rm -rf " + kTestDir;
+  ASSERT_EQ(system(deleteCmd.c_str()), 0);
+  options.max_log_file_size = 100 * 1024 * 1024;
+  options.create_if_missing = true;
+  ASSERT_OK(rocksdb::DB::Open(options, kTestDir, &db));
+  ASSERT_TRUE(env->FileExists(kLogFile));
+  delete db;
+}
+
 }  // namespace rocksdb
 
 int main(int argc, char** argv) {