一个轻巧高效的多线程c++stream风格异步日志(一)

一个轻巧高效的多线程c++stream风格异步日志


前言

本文主要实现muduo的异步日志.省去boost库中特性的引用,轻巧简洁。

对于编程而言,日志是必不可少的,对于关键进程,日志通常需要记录: 
1.收到的每条内部消息id. 
2.收到的每条外部消息全文. 
3.发出的每条消息全文,每条消息都有全局唯一的id. 
4.关键内部状态变更,等等. 
5.每条日志都有时间戳,以方便的追踪分布式系统中一个时间的来龙去脉.

c++日志大体上有两种API风格: 
C/JAVA的printf(fmt, ...)风格: 
log_info(“received %d bytes from %s”, len, getName.c_str()); 
c++的stream<<风格: 
LOG_INFO << “received << len << bytes from << getName.c_str();

本文实现的是c++的stream风格, 优点是使用起来更自然,不用保持格式的一致性.

功能需求

常规的通用日志库如log4j/logback通常会提供丰富的功能,但不一定是必须的功能.

1.日志有多种级别:TRACE、DEBUG、INFO、WARN、ERROR、FATAL等。 
2.日志可能会有多个目的地:文件、socket、SMTP等。 
3.日志消息格式可配置。 
4.可设置运行时过滤器(filter)、控制不同的组件的日志消息级别和目的地.

这四项中,除了第一项之外,其余并非是必须的功能.本文内容只包含第一项功能. 
对于分布式系统中的服务进程而言,日志的目的地只有一个:本地文件,往网络写日志消息是不可靠的,另一个坏处就是网络带宽的消耗.

muduo日志格式如下,本日志对格式有所改动,但基本信息不变。

日期 时间 微妙 线程 级别 函数名 正文 源文件名: 行号
20180802 12:42:50.621354 44321 WARN main just test - test.cpp:445
20180802 12:42:50.621359 44321 INFO main just test - test.cpp:446
20180802 12:42:50.621364 44321 ERROR main just test - test.cpp:447
  • 时间戳精确到微妙,每条消息通过gettimeofday(2)获取当前时间.这样做不会有什么性能损失,在x86-64Linux上,gettimeofday()不是系统调用,不会陷入内核
  • 打印线程ID,便于分析多线程程序时序,也可以检测死锁(未加入)
  • 打印日志级别,通过查看有无ERROR日志快速定位
  • 打印文件名和行号,修复问题不至于搞错对象
  • 每条日志尽量占一行,便于分析日志

性能需求

只有日志库足够高效,程序员才敢在代码中输出足够多的诊断信息,减小运维难度,提升效率.它体现在:

  • 每秒几千万条日志没有明显的性能损失
  • 能应对一个进程产生大量日志数据的场景,如1GB/min。
  • 不阻塞正常的执行流程
  • 在多线程程序中,不造成争用

为了实现性能指标,本日志设计中几点优化:

  • 时间戳字符串中的日期和时间两部分是缓存的,一秒之内的多条日志只需格式化微妙即可
  • 日志消息 的前四段是定长的,可避免运行时字串长度的计算
  • 线程id是预先格式化的字符串
  • 原文件名部分通过编译期计算来获得,避免运行期strrchr()的开销

Logger实现

LogStream类

LogStream类,主要作用是重载<<操作符,将基本类型的数据格式成字符串通过append接口存入LogBuffer中。

Alt text

#ifndef _LOG_STREAM_HH
#define _LOG_STREAM_HH
#include <stdio.h>
#include <string.h>
const int kSmallBuffer = 4096;
const int kLargeBuffer = 4096;
template<int SIZE>
class LogBuffer
{
public:
LogBuffer(): m_cur(m_data){
}
~LogBuffer(){
//printf("%s", m_data);
}
void append(const char* /*restrict*/ buf, size_t len){
// append partially
if (/*implicit_cast<size_t>*/(avail()) > len)
{
memcpy(m_cur, buf, len);
m_cur += len;
}
}
// write in m_data directly
char* current() { return m_cur; };
int avail() const { return static_cast<int> (end() - m_cur); }
void add(size_t len) { m_cur += len; }
int length() const {return m_cur - m_data;}
const char* data() const { return m_data; }
private:
const char* end() const { return m_data + sizeof(m_data); }
char m_data[SIZE];
char* m_cur;
};
class LogStream{
public:
LogStream();
~LogStream();
typedef LogBuffer<kSmallBuffer> Buffer;
typedef LogStream self;
self& operator<<(bool v);
self& operator<<(short);
self& operator<<(unsigned short);
self& operator<<(int);
self& operator<<(unsigned int);
self& operator<<(long);
self& operator<<(unsigned long);
self& operator<<(long long);
self& operator<<(unsigned long long);
self& operator<<(const void*);
self& operator<<(float v);
self& operator<<(double);
self& operator<<(char v);
self& operator<<(const char *);
void append(const char* data, int len) { return m_buffer.append(data, len); }
const Buffer& buffer() const { return m_buffer; }
private:
LogStream(const LogStream& ls); //no copyable
LogStream& operator=(const LogStream& ls);
template<typename T>
void formatInteger(T v);
Buffer m_buffer;
static const int kMaxNumericSize = 32;
};
class Fmt{
public:
template<typename T>
Fmt(const char* fmt, T val);
const char* data() const { return m_buf; }
int length() const { return m_length; }
private:
char m_buf[32];
int m_length;
};
inline LogStream& operator<<(LogStream &s, const Fmt& fmt){
s.append(fmt.data(), fmt.length());
return s;
}
#endif

Logger类

Logger类,使用LogStream的<<操作符将文件名,日志级别,时间等信息格式好提前写入LogBuffer中. 
它实际上是一个临时对象,通过宏定义临时构造一个logger对象,构造的时候即将上面信息写入LogBuffer,之后通过stream()接口引用LogStream的<<操作符写入我们的日志信息. 
优点是 :对于日志级别低的log那么它将是一个空的操作.

// CAUTION: do not write:
//
// if (good)
// LOG_INFO << "Good news";
// else
// LOG_WARN << "Bad news";
//
// this expends to
//
// if (good)
// if (logging_INFO)
// logInfoStream << "Good news";
// else
// logWarnStream << "Bad news";
//
#define LOG_TRACE if (Logger::logLevel() <= Logger::TRACE) \
Logger(__FILE__, __LINE__, Logger::TRACE, __func__).stream()
#define LOG_DEBUG if (Logger::logLevel() <= Logger::DEBUG) \
Logger(__FILE__, __LINE__, Logger::DEBUG, __func__).stream()
#define LOG_INFO if (Logger::logLevel() <= Logger::INFO) \
Logger(__FILE__, __LINE__).stream()
#define LOG_WARN Logger(__FILE__, __LINE__, Logger::WARN).stream()
#define LOG_ERROR Logger(__FILE__, __LINE__, Logger::ERROR).stream()
#define LOG_FATAL Logger(__FILE__, __LINE__, Logger::FATAL).stream()
#define LOG_SYSERR Logger(__FILE__, __LINE__, false).stream()
#define LOG_SYSFATAL Logger(__FILE__, __LINE__, true).stream()

它的成员结构如下图所示: 
Impl对象是个私有类,主要是为了闭源,构造Impl的时候后写入时间戳,日志级别,文件名等等. 
logLevel()、setlogLevel()、为两个静态成员函数,用于设置日志级别. 
setOutput()也是个静态成员函数,主要作用是重定向日志的输出.默认是输出至stdout.

Alt text

#ifndef _LOGGER_HH
#define _LOGGER_HH
#include <string.h>
#include "LogStream.hh"
#include "TimeStamp.hh"
// CAUTION: do not write:
//
// if (good)
// LOG_INFO << "Good news";
// else
// LOG_WARN << "Bad news";
//
// this expends to
//
// if (good)
// if (logging_INFO)
// logInfoStream << "Good news";
// else
// logWarnStream << "Bad news";
//
#define LOG_TRACE if (Logger::logLevel() <= Logger::TRACE) \
Logger(__FILE__, __LINE__, Logger::TRACE, __func__).stream()
#define LOG_DEBUG if (Logger::logLevel() <= Logger::DEBUG) \
Logger(__FILE__, __LINE__, Logger::DEBUG, __func__).stream()
#define LOG_INFO if (Logger::logLevel() <= Logger::INFO) \
Logger(__FILE__, __LINE__).stream()
#define LOG_WARN Logger(__FILE__, __LINE__, Logger::WARN).stream()
#define LOG_ERROR Logger(__FILE__, __LINE__, Logger::ERROR).stream()
#define LOG_FATAL Logger(__FILE__, __LINE__, Logger::FATAL).stream()
#define LOG_SYSERR Logger(__FILE__, __LINE__, false).stream()
#define LOG_SYSFATAL Logger(__FILE__, __LINE__, true).stream()
class Logger
{
public:
enum LogLevel
{
TRACE,
DEBUG,
INFO,
WARN,
ERROR,
FATAL,
NUM_LOG_LEVELS,
};
//compile time calculation of basename of source file
class SourceFile
{
public:
template<int N>
inline SourceFile(const char (&arr)[N])
:m_data(arr),
m_size(N-1){
const char* slash = strrchr(m_data, '/'); // builtin function
if (slash){
m_data = slash + 1;
m_size -= static_cast<int>(m_data - arr);
}
}
explicit SourceFile(const char* filename)
: m_data(filename){
const char* slash = strrchr(filename, '/');
if (slash){
m_data = slash + 1;
}
m_size = static_cast<int>(strlen(m_data));
}
const char* m_data;
int m_size;
};
Logger(SourceFile file, int line);
Logger(SourceFile file, int line, LogLevel level);
Logger(SourceFile file, int line, LogLevel level, const char* func);
Logger(SourceFile file, int line, bool toAbort);
~Logger();
static void setLogLevel(LogLevel level);
static LogLevel logLevel();
LogStream& stream() { return m_impl.m_stream; }
typedef void (*outputFunc)(const char *msg, int len);
typedef void (*flushFunc)();
static void setOutput(outputFunc);
static void setFlush(flushFunc);
private:
Logger(const Logger &lg); //no copyable
Logger& operator=(const Logger &lg);
class Impl
{
public:
typedef Logger::LogLevel LogLevel;
Impl(LogLevel level, int old_errno, const SourceFile& file, int line);
void formatTime();
void finish();
TimeStamp m_time;
LogStream m_stream;
LogLevel m_level;
int m_line;
SourceFile m_fileBaseName;
};
Impl m_impl;
};
#endif

完成Logger即可直接使用了。 
直接通过宏LOG_DEBUG << 即可打印格式化好的日志信息. 只是默认输出到stdout. 
后面文章会给出日志文件类及异步线程类的实现.

LogStream及Logger cpp源码

//LogStream
#include <stdio.h>
#include <assert.h>
#include <algorithm>
#include "LogStream.hh"
LogStream::LogStream(){
}
LogStream::~LogStream(){
}
LogStream& LogStream::operator<<(bool v){
m_buffer.append(v ? "1" : "0", 1);
return *this;
}
LogStream& LogStream::operator<<(short v){
*this << static_cast<int>(v);
return *this;
}
LogStream& LogStream::operator<<(unsigned short v)
{
*this << static_cast<unsigned int>(v);
return *this;
}
LogStream& LogStream::operator<<(int v)
{
formatInteger(v);
return *this;
}
LogStream& LogStream::operator<<(unsigned int v)
{
formatInteger(v);
return *this;
}
LogStream& LogStream::operator<<(long v)
{
formatInteger(v);
return *this;
}
LogStream& LogStream::operator<<(unsigned long v)
{
formatInteger(v);
return *this;
}
LogStream& LogStream::operator<<(long long v)
{
formatInteger(v);
return *this;
}
LogStream& LogStream::operator<<(unsigned long long v)
{
formatInteger(v);
return *this;
}
LogStream& LogStream::operator<<(const void*){
printf("undefine\n");
}
LogStream& LogStream::operator<<(float v)
{
*this << static_cast<double>(v);
return *this;
}
LogStream& LogStream::operator<<(double v){
if(m_buffer.avail() >= kMaxNumericSize){
int len = snprintf(m_buffer.current(), kMaxNumericSize, "%.12g", v);
m_buffer.add(len);
}
return *this;
}
LogStream& LogStream::operator<<(char v){
m_buffer.append(&v, 1);
return *this;
}
LogStream& LogStream::operator<<(const char *str){
if(str){
m_buffer.append(str, strlen(str));
}else{
m_buffer.append("(NULL)", 6);
}
return *this;
}
const char digits[] = "9876543210123456789";
const char* zero = digits + 9;
//convert to str
template<typename T>
size_t convert(char buf[], T value){
T i = value;
char *p = buf;
do{
int lsd = static_cast<int>(i % 10);
i /= 10;
*p++ = zero[lsd];
} while(i != 0);
if(value < 0){
*p++ = '-';
}
*p = '\0';
std::reverse(buf, p);
return p - buf;
}
template<typename T>
void LogStream::formatInteger(T v)
{
if(m_buffer.avail() >= kMaxNumericSize){
size_t len = convert(m_buffer.current(), v);
m_buffer.add(len);
}
}
template<typename T>
Fmt::Fmt(const char* fmt, T val)
{
m_length = snprintf(m_buf, sizeof(m_buf), fmt, val);
assert(static_cast<size_t>(m_length) < sizeof(m_buf));
}
// Explicit instantiations
template Fmt::Fmt(const char* fmt, char);
template Fmt::Fmt(const char* fmt, short);
template Fmt::Fmt(const char* fmt, unsigned short);
template Fmt::Fmt(const char* fmt, int);
template Fmt::Fmt(const char* fmt, unsigned int);
template Fmt::Fmt(const char* fmt, long);
template Fmt::Fmt(const char* fmt, unsigned long);
template Fmt::Fmt(const char* fmt, long long);
template Fmt::Fmt(const char* fmt, unsigned long long);
template Fmt::Fmt(const char* fmt, float);
template Fmt::Fmt(const char* fmt, double);
//Logger
#include <time.h>
#include <stdint.h>
#include <stdlib.h>
#include <assert.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include "TimeStamp.hh"
#include "Logger.hh"
__thread char t_time[64];
__thread time_t t_lastSecond;
__thread char t_errnobuf[512];
const char* strerror_tl(int savedErrno)
{
return strerror_r(savedErrno, t_errnobuf, sizeof(t_errnobuf));
}
Logger::LogLevel g_logLevel = Logger::INFO;
void Logger::setLogLevel(LogLevel level){
g_logLevel = level;
}
Logger::LogLevel Logger::logLevel(){
return g_logLevel;
}
const char* LogLevelName[Logger::NUM_LOG_LEVELS] =
{
"[TRACE]",
"[DEBUG]",
"[INFO ]",
"[WARN ]",
"[ERROR]",
"[FATAL]",
};
// helper class for known string length at compile time
class T
{
public:
T(const char* str, unsigned len)
:m_str(str),
m_len(len)
{
assert(strlen(str) == m_len);
}
const char* m_str;
const unsigned m_len;
};
void defaultOutput(const char *msg, int len){
size_t n = fwrite(msg, 1, len, stdout);
(void)n;
}
void defaultFlush(){
fflush(stdout);
}
Logger::outputFunc g_output = defaultOutput;
Logger::flushFunc g_flush = defaultFlush;
void Logger::setOutput(outputFunc out){
g_output = out;
}
void Logger::setFlush(flushFunc flush){
g_flush = flush;
}
Logger::Logger(SourceFile file, int line)
: m_impl(INFO, 0, file, line){
}
Logger::Logger(SourceFile file, int line, LogLevel level)
: m_impl(level, 0, file, line){
}
Logger::Logger(SourceFile file, int line, bool toAbort)
: m_impl(toAbort? FATAL:ERROR, errno, file, line){
}
Logger::Logger(SourceFile file, int line, LogLevel level, const char* func)
: m_impl(level, 0, file, line){
m_impl.m_stream << '[' << func << "] ";
}
Logger::~Logger(){
m_impl.finish();
const LogStream::Buffer& buf(stream().buffer());
g_output(buf.data(), buf.length());
if (m_impl.m_level == FATAL)
{
g_flush();
abort();
}
}
Logger::Impl::Impl(LogLevel level, int savedErrno, const SourceFile& file, int line)
: m_time(TimeStamp::now()),
m_stream(),
m_level(level),
m_fileBaseName(file),
m_line(line)
{
formatTime();
m_stream << LogLevelName[level] << ' ';
m_stream << '[' << m_fileBaseName.m_data << ':' << m_line << "] ";
if (savedErrno != 0)
{
m_stream << strerror_tl(savedErrno) << " (errno=" << savedErrno << ") ";
}
}
void Logger::Impl::finish()
{
m_stream<< '\n';
}
void Logger::Impl::formatTime()
{
int64_t microSecondsSinceEpoch = m_time.microSecondsSinceEpoch();
time_t seconds = static_cast<time_t>(microSecondsSinceEpoch / TimeStamp::kMicroSecondsPerSecond);
int microseconds = static_cast<int>(microSecondsSinceEpoch % TimeStamp::kMicroSecondsPerSecond);
if (seconds != t_lastSecond){
t_lastSecond = seconds;
struct tm tm_time;
::gmtime_r(&seconds, &tm_time); // FIXME TimeZone::fromUtcTime
int len = snprintf(t_time, sizeof(t_time), "%4d-%02d-%02d %02d:%02d:%02d",
tm_time.tm_year + 1900, tm_time.tm_mon + 1, tm_time.tm_mday,
tm_time.tm_hour + 8, tm_time.tm_min, tm_time.tm_sec);
assert(len == 19); (void)len;
}
Fmt us(".%06d ", microseconds);
assert(us.length() == 8);
m_stream << t_time << us.data();
}
作者 —— 靑い空゛

出处:http://www.cnblogs.com/ailumiyana/

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posted @ 2018-08-24 09:01  靑い空゛  阅读(1702)  评论(0编辑  收藏  举报