提升日志和严重性/本地属性(Boost log and severity / local attributes)

提升日志和严重性/本地属性(Boost log and severity / local attributes)

我是Boost日志的新手。 我有一些简单的工作，但我坚持使用宏来轻松指定文件名和行号。 这看起来很难，我想我错过了什么。

我写这篇文章是为了在最后使用演示日志初始化日志记录。 请注意，我正在登录到控制台和旋转文件。

logging::add_console_log(std::clog, keywords::format = "%TimeStamp%: %_%", keywords::auto_flush = true); typedef sinks::synchronous_sink<sinks::text_file_backend> file_sink; shared_ptr<file_sink> sink(new file_sink( keywords::file_name = "%Y%m%d_%H%M%S_%5N.log", keywords::rotation_size = 16384, keywords::auto_flush = true)); sink->locked_backend()->set_file_collector(sinks::file::make_collector( keywords::target = "logs", keywords::max_size = 16 * 1024 * 1024, keywords::min_free_space = 100 * 1024 * 1024)); sink->locked_backend()->scan_for_files(); sink->set_formatter(expr::stream << expr::attr<boost::posix_time::ptime>("TimeStamp") << " " << logging::trivial::severity << "[" << expr::attr<string>("FileName") << ":" << expr::attr<unsigned int>("LineNumber") << "] " << expr::smessage); logging::core::get()->add_sink(sink); logging::add_common_attributes(); logging::core::get()->add_global_attribute("TimeStamp", attrs::local_clock()); src::severity_logger<logging::trivial::severity_level> slg; lg.add_attribute("LineNumber", attrs::constant<unsigned int>(__LINE__)); lg.add_attribute("FileName", attrs::constant<string>(__FILE__)); for (unsigned int i = 0; i < 5; ++i) { BOOST_LOG_SEV(slg, logging::trivial::info) << "Some log record"; }

现在我想创建一个宏，以便我可以添加文件和行号，并使其行为像ostream。 我希望能做的就是说

LOG(info) << "Hello, world!";

我编写了以下内容，但这不起作用，但它表达了我正在尝试做的事情：

#define LOG(severity_level) LogMessage(__FILE__, __LINE__, severity_level) // What's my return type? auto LogMessage(const char* filename, const int line_number, const enum SeverityLevel) { src::severity_logger slg; slg.add_attribute("LineNumber", attrs::constant<unsigned int>(__LINE__)); slg.add_attribute("FileName", attrs::constant<string>(__FILE__)); return BOOST_LOG_SEV(slg, severity_level); // NO }

I'm new to Boost log. I've got some simple stuff working but I'm stuck at getting a macro to make it easy to specify filename and line number. It's seeming so hard, I assume I've missed something.

I wrote this to initialize logging with a demo log at the end. Note that I'm logging to console and to a rotating file.

logging::add_console_log(std::clog, keywords::format = "%TimeStamp%: %_%", keywords::auto_flush = true); typedef sinks::synchronous_sink<sinks::text_file_backend> file_sink; shared_ptr<file_sink> sink(new file_sink( keywords::file_name = "%Y%m%d_%H%M%S_%5N.log", keywords::rotation_size = 16384, keywords::auto_flush = true)); sink->locked_backend()->set_file_collector(sinks::file::make_collector( keywords::target = "logs", keywords::max_size = 16 * 1024 * 1024, keywords::min_free_space = 100 * 1024 * 1024)); sink->locked_backend()->scan_for_files(); sink->set_formatter(expr::stream << expr::attr<boost::posix_time::ptime>("TimeStamp") << " " << logging::trivial::severity << "[" << expr::attr<string>("FileName") << ":" << expr::attr<unsigned int>("LineNumber") << "] " << expr::smessage); logging::core::get()->add_sink(sink); logging::add_common_attributes(); logging::core::get()->add_global_attribute("TimeStamp", attrs::local_clock()); src::severity_logger<logging::trivial::severity_level> slg; lg.add_attribute("LineNumber", attrs::constant<unsigned int>(__LINE__)); lg.add_attribute("FileName", attrs::constant<string>(__FILE__)); for (unsigned int i = 0; i < 5; ++i) { BOOST_LOG_SEV(slg, logging::trivial::info) << "Some log record"; }

Now I'd like to make a macro so that I can add file and line number and have it behave like an ostream. What I'd like to be able to do is say

LOG(info) << "Hello, world!";

I wrote the following, which doesn't work, but it expresses what I'm trying to do:

#define LOG(severity_level) LogMessage(__FILE__, __LINE__, severity_level) // What's my return type? auto LogMessage(const char* filename, const int line_number, const enum SeverityLevel) { src::severity_logger slg; slg.add_attribute("LineNumber", attrs::constant<unsigned int>(__LINE__)); slg.add_attribute("FileName", attrs::constant<string>(__FILE__)); return BOOST_LOG_SEV(slg, severity_level); // NO }

最满意答案

这里回答了类似的问题，我只是重复我的建议。

最简单的解决方案是定义您自己的日志记录宏，它将在消息前面添加源文件中的位置。 例如： #define LOG(lg, sev)\ BOOST_LOG_SEV(lg, sev) << "[" << __FILE__ << ":" << __LINE__ << "]: "

现在，您可以在代码中的任何位置使用此宏而不是BOOST_LOG_SEV 。 此解决方案的缺点是您不能将文件和行用作属性，因此日志格式是固定的。

使用流操纵器将文件名和行号附加为属性。 同样，在宏中更容易做到这一点： BOOST_LOG_ATTRIBUTE_KEYWORD(a_file, "File", std::string) BOOST_LOG_ATTRIBUTE_KEYWORD(a_line, "Line", unsigned int) #define LOG(lg, sev)\ BOOST_LOG_SEV(lg, sev) << logging::add_value(a_file, __FILE__) << logging::add_value(a_line, __LINE__)

（请参阅此处有关关键字。）执行此操作后，您可以在格式化程序中使用这些属性：

sink->set_formatter( expr::stream << "[" << a_file << ":" << a_line << "]: " << expr::message);

以这种方式添加的属性不能在过滤器中使用，如果这是一个问题，你可以......

使用范围属性 。 同样，您可以定义一个宏来自动化该过程： #define LOG(lg, sev, strm)\ do {\ BOOST_LOG_SCOPED_LOGGER_ATTR(lg, a_file.get_name(), attrs::constant< tag::a_file::value_type >(__FILE__));\ BOOST_LOG_SCOPED_LOGGER_ATTR(lg, a_line.get_name(), attrs::constant< tag::a_line::value_type >(__LINE__));\ BOOST_LOG_SEV(lg, sev) strm;\ } while (false)

请注意，在这种情况下，流表达式作为参数传递给宏，因为我们需要将它注入范围的中间。 另请注意，此解决方案可能性能低于其他两个。

确实没有一个解决方案在某些时候不涉及宏，因为__FILE__和__LINE__是在使用点展开的宏。 我相信，这是您的代码中的一个问题，您在LogMessage函数中使用了宏。

这是因为无论如何都必须定义宏，这些宏应该是用户特定的，Boost.Log不提供开箱即用的功能。

This answer owes quite a lot to these conversations and to the solution proposed by @guillermo-ruiz in particular. I chose to follow Guillermo's suggestions because it made the least use of the preprocessor. (Some use of the preprocessor is mandatory, of course, since I wanted __FILE__ and __LINE__.)

In the interest of offering to those who follow somewhat broader help than just a strict answer, a couple remarks:

Yes, it's very strange that Boost log doesn't provide this out of the box. Boost log doesn't do as much error checking as I'd like. In particular, if one has a mismatch between the name of an attribute at definition and the name at use, the result is a segfault without descriptive error, not a runtime error (followed by abort or not). Boost log is remarkably sensitive to getting include statements correct. There's no single include to rule them all, and missing an include leads to error messages suggesting a programming error when, in fact, it's merely a missing definition.

In the file log.cc, I wrote this:

Log::Log() { try { // The first thing we have to do to get using the library is // to set up the logging sinks - i.e. where the logs will be written to. logging::add_console_log(std::clog, keywords::format = "%TimeStamp%: %_%", keywords::auto_flush = true); // Create a text file sink typedef sinks::synchronous_sink<sinks::text_file_backend> file_sink; shared_ptr<file_sink> sink(new file_sink( // File name pattern. keywords::file_name = "%Y%m%d_%H%M%S_%5N.log", // Rotation size, in characters keywords::rotation_size = 16384, // Rotate daily if not more often. The time is arbitrary. keywords::time_based_rotation = sinks::file::rotation_at_time_point(4, 33, 17), // Flush after write. keywords::auto_flush = true)); // Set up where the rotated files will be stored. sink->locked_backend()->set_file_collector(sinks::file::make_collector( // Where to store rotated files. keywords::target = "logs", // Maximum total size of the stored files, in bytes. keywords::max_size = 16 * 1024 * 1024, // Minimum free space on the drive, in bytes. keywords::min_free_space = 100 * 1024 * 1024)); // Upon restart, scan the target directory for files matching the // file_name pattern. sink->locked_backend()->scan_for_files(); boost::log::register_simple_formatter_factory< logging::trivial::severity_level, char>("Severity"); sink->set_formatter(expr::stream << expr::attr<boost::posix_time::ptime>("TimeStamp") << " " << logging::trivial::severity << "[" << expr::attr<string>("FileName") << ":" << expr::attr<unsigned int>("LineNumber") << "] " << expr::smessage); // Add it to the core logging::core::get()->add_sink(sink); // Add some attributes too logging::add_common_attributes(); logging::core::get()->add_global_attribute("TimeStamp", attrs::local_clock()); logging::core::get()->add_global_attribute( "LineNumber", attrs::mutable_constant<unsigned int>(5)); logging::core::get()->add_global_attribute( "FileName", attrs::mutable_constant<string>("")); src::severity_logger<logging::trivial::severity_level> slg; slg.add_attribute("LineNumber", attrs::constant<unsigned int>(__LINE__)); slg.add_attribute("FileName", attrs::constant<string>(__FILE__)); for (unsigned int i = 0; i < 2; ++i) { BOOST_LOG_SEV(slg, logging::trivial::info) << "Testing log, #" << i; } } catch (std::exception& e) { std::cerr << "Failed to establish logging: " << e.what() << std::endl; throw LoggingInitException(); } } Log::~Log() { boost::log::core::get()->remove_all_sinks(); } string PathToFilename(const string& path) { string sub_path = path.substr(path.find_last_of("/\\") + 1); return sub_path; }

In the file log.h, I wrote this:

// An exception if logging fails to initialize. class LoggingInitException : public std::exception {}; /* Class to set up logging as we want it in all services. Instantiate a Log object near the beginning of main(). */ class Log { public: Log(); ~Log(); }; // Logging macro that includes severity, filename, and line number. // Copied and modified from // https://stackoverflow.com/questions/24750218/boost-log-to-print-source-code-file-name-and-line-number // Set attribute and return the new value template <typename ValueType> ValueType SetGetAttrib(const char* name, ValueType value) { auto attr = boost::log::attribute_cast< boost::log::attributes::mutable_constant<ValueType>>( boost::log::core::get()->get_global_attributes()[name]); attr.set(value); return attr.get(); } // Convert file path to only the filename std::string PathToFilename(const std::string& path); // Shortcut to declare a log source. To insert in each function that will call // the LOG macro. #define LOGGABLE \ boost::log::sources::severity_logger<boost::log::trivial::severity_level> \ slg; #define LOG(sev) \ BOOST_LOG_STREAM_WITH_PARAMS( \ (slg), \ (SetGetAttrib("FileName", PathToFilename(__FILE__)))( \ SetGetAttrib("LineNumber", (unsigned int)__LINE__))( \ ::boost::log::keywords::severity = (boost::log::trivial::sev)))

Then, to log from file foo.cc, I do this:

void MyFunction() { LOGGABLE; LOG(debug) << "I made it to MyFunction()."; } int main(int argc, char *argv[]) { Log log; LOGGABLE; LOG(info) << "Hey, I'm a message!"; MyFunction(); return 0; }

A few quibbles remain, but they are out of scope for this SO question/answer:

To make this more usable, I should make logs go somewhere more specific than "logs", probably directed by invocation flags and the application name, whether I'm in production or not, etc. I should check if stdout is connected to a terminal and if not, skip logging to stdout. Or I should provide a flag to disable it in data centers, at least. Sometimes, mysteriously, I get a top level log file called (for example) 20160310_093628_00000.log instead of a file written to the logs/ directory. It took me a long time to realize that boost log writes there, then rotates to the logs/ directory. So if the program crashes, I end up with a log file at that level.