spdlog

Very fast, header only, C++ logging library.  

Install

Just copy the headers:

• Copy the source folder to your build tree and use a C++11 compiler.

Or use your favourite package manager:

• Ubuntu: apt-get install libspdlog-dev
• Homebrew: brew install spdlog
• FreeBSD: cd /usr/ports/devel/spdlog/ && make install clean
• Fedora: yum install spdlog
• Arch Linux: pacman -S spdlog-git
• vcpkg: vcpkg install spdlog

Platforms

• Linux, FreeBSD, Solaris
• Windows (vc 2013+, cygwin/mingw)
• Mac OSX (clang 3.5+)
• Android

Features

• Very fast - performance is the primary goal (see benchmarks below).
• Headers only, just copy and use.
• Feature rich call style using the excellent fmt library.
• Extremely fast asynchronous mode (optional) - using lockfree queues and other tricks to reach millions of calls/sec.
• Custom formatting.
• Conditional Logging
• Multi/Single threaded loggers.
• Various log targets:
  • Rotating log files.
  • Daily log files.
  • Console logging (colors supported).
  • syslog.
  • Windows debugger (OutputDebugString(..))
  • Easily extendable with custom log targets (just implement a single function in the sink interface).
• Severity based filtering - threshold levels can be modified in runtime as well as in compile time.

Benchmarks

Below are some benchmarks comparing popular log libraries under Ubuntu 64 bit, Intel i7-4770 CPU @ 3.40GHz

Synchronous mode

Time needed to log 1,000,000 lines in synchronous mode (in seconds, the best of 3 runs):

threads	boost log 1.54	glog	easylogging	spdlog
1	4.169s	1.066s	0.975s	0.302s
10	6.180s	3.032s	2.857s	0.968s
100	5.981s	1.139s	4.512s	0.497s

Asynchronous mode

Time needed to log 1,000,000 lines in asynchronous mode, i.e. the time it takes to put them in the async queue (in seconds, the best of 3 runs):

threads	g2log async logger	spdlog async mode
1	1.850s	0.216s
10	0.943s	0.173s
100	0.959s	0.202s

Usage Example

#include "spdlog/spdlog.h"

#include <iostream>
#include <memory>

void async_example();
void syslog_example();
void user_defined_example();
void err_handler_example();

namespace spd = spdlog;
int main(int, char*[])
{
    try
    {
        // Console logger with color
        auto console = spd::stdout_color_mt("console");
        console->info("Welcome to spdlog!");
        console->error("Some error message with arg{}..", 1);

	// Conditional logging example
        auto i = 2;
        console->info_if(i < 20, "Welcome to spdlog conditional logging!");
        console->warn_if(i != 0, "an important message");
        console->critical_if(i != 2, "a false warning which won't show up");

        // Formatting examples
        console->warn("Easy padding in numbers like {:08d}", 12);
        console->critical("Support for int: {0:d};  hex: {0:x};  oct: {0:o}; bin: {0:b}", 42);
        console->info("Support for floats {:03.2f}", 1.23456);
        console->info("Positional args are {1} {0}..", "too", "supported");
        console->info("{:<30}", "left aligned");
        

        spd::get("console")->info("loggers can be retrieved from a global registry using the spdlog::get(logger_name) function");
        
        // Create basic file logger (not rotated)
        auto my_logger = spd::basic_logger_mt("basic_logger", "logs/basic.txt");
        my_logger->info("Some log message");

        // Create a file rotating logger with 5mb size max and 3 rotated files
        auto rotating_logger = spd::rotating_logger_mt("some_logger_name", "logs/mylogfile", 1048576 * 5, 3);
        for (int i = 0; i < 10; ++i)
            rotating_logger->info("{} * {} equals {:>10}", i, i, i*i);

        // Create a daily logger - a new file is created every day on 2:30am
        auto daily_logger = spd::daily_logger_mt("daily_logger", "logs/daily", 2, 30);
        // trigger flush if the log severity is error or higher
        daily_logger->flush_on(spd::level::err);
        daily_logger->info(123.44);

        // Customize msg format for all messages
        spd::set_pattern("*** [%H:%M:%S %z] [thread %t] %v ***");
        rotating_logger->info("This is another message with custom format");


        // Runtime log levels
	spd::set_level(spd::level::info); //Set global log level to info
	console->debug("This message shold not be displayed!");
	console->set_level(spd::level::debug); // Set specific logger's log level
	console->debug("This message shold be displayed..");

        // Compile time log levels
        // define SPDLOG_DEBUG_ON or SPDLOG_TRACE_ON
        SPDLOG_TRACE(console, "Enabled only #ifdef SPDLOG_TRACE_ON..{} ,{}", 1, 3.23);
        SPDLOG_DEBUG(console, "Enabled only #ifdef SPDLOG_DEBUG_ON.. {} ,{}", 1, 3.23);

        // Asynchronous logging is very fast..
        // Just call spdlog::set_async_mode(q_size) and all created loggers from now on will be asynchronous..
        async_example();

        // syslog example. linux/osx only
        syslog_example();

        // android example. compile with NDK
        android_example();

        // Log user-defined types example
        user_defined_example();

        // Change default log error handler
        err_handler_example();

        // Apply a function on all registered loggers
        spd::apply_all([&](std::shared_ptr<spd::logger> l)
        {
            l->info("End of example.");
        });

        // Release and close all loggers
        spd::drop_all();
    }
    // Exceptions will only be thrown upon failed logger or sink construction (not during logging)
    catch (const spd::spdlog_ex& ex)
    {
        std::cout << "Log init failed: " << ex.what() << std::endl;
        return 1;
    }
}

void async_example()
{
    size_t q_size = 4096; //queue size must be power of 2
    spd::set_async_mode(q_size);
    auto async_file = spd::daily_logger_st("async_file_logger", "logs/async_log.txt");
    for (int i = 0; i < 100; ++i)
        async_file->info("Async message #{}", i);
}

//syslog example
void syslog_example()
{
#ifdef SPDLOG_ENABLE_SYSLOG 
    std::string ident = "spdlog-example";
    auto syslog_logger = spd::syslog_logger("syslog", ident, LOG_PID);
    syslog_logger->warn("This is warning that will end up in syslog..");
#endif
}

// user defined types logging by implementing operator<<
struct my_type
{
    int i;
    template<typename OStream>
    friend OStream& operator<<(OStream& os, const my_type &c)
    {
        return os << "[my_type i="<<c.i << "]";
    }
};

#include <spdlog/fmt/ostr.h> // must be included
void user_defined_example()
{
    spd::get("console")->info("user defined type: {}", my_type { 14 });
}

//
//custom error handler
//
void err_handler_example()
{	
	spd::set_error_handler([](const std::string& msg) {
		std::cerr << "my err handler: " << msg << std::endl;
	}); 
	// (or logger->set_error_handler(..) to set for specific logger)
}

Documentation

Documentation can be found in the wiki pages.