假如让你自己去写一个日志程序，我想最原始且简单的想法因该是，首先将要写入日志文件的内容转化为字符串，然后调用write系统调用将其写入文件。这种实现方法的确就是我们程序最原始的日志方法。这种做法无疑是十分低效的，那么如何让我们的日志能够高效起来呢？本篇博文就是要给大家分享一种高效的日志–异步日志
1.异步日志要实现什么?
前言中我有告诉打下那种最原始且简单的日志方法很低效，那么它低效在什么地方了呢？
主要有如下几点
1.其每条日志内容都会调用write,我们都知道write为系统调用，每一条就调一次它，势必系统开销会很大
2.当我们在关键的地方调用write会不会导致关键部分的代码不能即使的执行?
上述俩个导致我们原始日志低效的主要原因的解决方案分别为:
(1)既然每条日志调用一次write会导致系统开销变大，那么我们就设计一个buffer将日志内容保存在buffer中，待buffer满之后在一次性调用write将其写入即可
(2)由于write可能会阻塞在当前位置，导致紧随其后的关键代码可能不能马上执行，那么我们就单独开个线程专门来执行write调用不就可以了么
根据我们的解决方案，我们可以总结出异步日志的基本流程因该为:
前段线程(我们的程序)负责将日志写入buffer中，当buffer写满之后，将buffer转交给后端线程(我们的负责专门调用write来写日志的线程)，也就是一个典型的多生产者单消费者模式
2.异步日志的代码实现
接下来为大家介绍一下我用C++实现的的异步日志代码
(1)buffer类的实现
#ifndef FIX_BUFFER_H_
#define FIX_BUFFER_H_
#include <vector>
#include <string>
#include <assert.h>
#include <fcntl.h>
namespace netlib
{
class FixBuffer
{
public:
FixBuffer()
:buffer_(1024*1024*4) //初始化大小为4M
{
readableIndex_ = 0;
writeableIndex_ = 0;
}
~FixBuffer()
{
}
int readableSize(void) //可读字节数
{
return writeableIndex_ - readableIndex_;
}
int writeableSize(void) //可写字节数
{
return buffer_.size() - writeableIndex_;
}
void append(const char *data,int len) //添加数据到buffer中
{
std::copy(data,data + len,getWritePeek());
moveWriteIndex(len);
}
char *getReadPeek(void) //获得读位置的指针
{
return begin() + readableIndex_;
}
char *getWritePeek(void) //获得写位置的指针
{
return begin() + writeableIndex_;
}
void moveWriteIndex(int len) //移动可写下标
{
writeableIndex_ = writeableIndex_ + len;
}
void resetBuffer(void) //重置buffer
{
readableIndex_ = 0;
writeableIndex_ = 0;
}
private:
char *begin()
{
return &*buffer_.begin();
}
std::vector<char> buffer_;
int readableIndex_;
int writeableIndex_;
};
}
#endifbuffer用std::vector来实现，主要提供的对外接口为获取buffer的读写位置指针，可读可写的大小，往buffer中添加数据等，buffer为固定大小4M
(2)用于将日志写如文件的类
logfile.h
#ifndef LOG_FILE_H_
#define LOG_FILE_H_
namespace netlib
{
class LogFile
{
public:
LogFile(int rollSize);
~LogFile();
//往磁盘里添加消息
void append(char *log,int len);
//滚动文件
void rollFile(int curLen);
private:
int rollSize_; //文件滚动大小
int fd_;
int fillSize_; //当前文件填充大小
int fileNumbers_; //已有文件数量
};
}
#endif
logfile类的实现
#include "logFile.h"
#include <stdio.h>
#include <assert.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <sys/stat.h>
using namespace netlib;
LogFile::LogFile(int rollSize)
:rollSize_(rollSize),
fillSize_(0),
fileNumbers_(1)
{
fd_ = open("/home/shreck/log/mylog.log",O_WRONLY | O_APPEND | O_CREAT,S_IWUSR | S_IRUSR | S_IXUSR);
assert(fd_ > 0);
}
LogFile::~LogFile()
{
close(fd_);
}
void LogFile::append(char *log,int len)
{
int ret = write(fd_,log,len);
rollFile(ret);
assert(ret == len);
}
void LogFile::rollFile(int curLen)
{
fillSize_ += curLen;
if(fillSize_ >= rollSize_)
{
printf("1G满了\n");
//置0fillSize_
fillSize_ = 0;
char command[80];
snprintf(command,sizeof(command),"mv /home/shreck/log/mylog.log /home/shreck/log/mylog%d.log",fileNumbers_);
fileNumbers_++;
//改当前文件名为fileName
system(command);
//重新创建一个mylog.log文件
fd_ = open("/home/shreck/log/mylog.log",O_WRONLY | O_APPEND | O_CREAT,S_IWUSR | S_IRUSR | S_IXUSR);
assert(fd_ > 0);
}
}(3)时间戳类的实现
#ifndef TIMESTAMP_H_
#define TIMESTAMP_H_
#include <time.h>
#include <string.h>
#include <sys/time.h>
#include <stdio.h>
#include <stdlib.h>
#include <string>
namespace netlib
{
class Timestamp
{
public:
Timestamp()
{
}
~Timestamp()
{
}
static struct tm now(void) //获取当前tm格式的时间
{
struct timeval tv;
struct tm time;
gettimeofday(&tv,NULL); //获取微妙，秒值
gmtime_r(&tv.tv_sec,&time); //将s转换为tm格式
time.tm_year += 1900;
return time;
}
static timeval getTime(void)
{
struct timeval tv;
gettimeofday(&tv,NULL);
return tv;
}
char *toStringTime(void) //将时间转化为字符串并返回
{
struct tm time;
bzero(str_,sizeof(str_));
time = now();
snprintf(str_,sizeof(str_),"%d-%d-%d %d:%d:%d ",time.tm_year,time.tm_mon,time.tm_mday,time.tm_hour,time.tm_min,time.tm_sec);
printf("%s",str_);
return str_;
}
static int getTimeDiff(timeval v1,timeval v2) //获得俩时间的时间差,返回值为微妙
{
int t;
t = v1.tv_sec*1000000 + v1.tv_usec - v2.tv_sec*1000000 - v2.tv_usec;
t = abs(t);
return t;
}
private:
char str_[100];
};
}
#endif(4)异步日志类的实现
异步日志类的定义
#ifndef ASYNLOG_H_
#define ASYNLOG_H_
#include <memory>
#include "fixBuffer.h"
#include "timestamp.h"
#include <vector>
#include <thread>
#include <string>
#include <mutex>
#include <condition_variable>
namespace netlib
{
enum LogLevel
{
OFF, //关闭所有日志记录
FATAL, //导致程序退出的错误
ERROE, //发生了错误但不影响系统运行
WARN, //会出现潜在的错误情形
INFO, //系统发生了那些事情
DEBUG, //调试程序有关的信息
ALL, //输出所有日志记录
};
class AsynLog
{
public:
AsynLog(int roolSize);
~AsynLog();
void append(char *logline,int len,LogLevel level); //添加日志行
void setLevel(LogLevel level); //设置日志的水平
void stop(void); //关闭日志
private:
void threadFunc(void); //线程函数
bool aboveLevel(LogLevel level); //判断某条日志等级是否超过我们所设的level
void writeBuffer(const char* logline,int len); //将日志内容写入buffer中
std::string toStringForLevel(LogLevel level); //将对应的level转化为字符串
int rollSize_; //文件达到多大时滚动
bool running_;
std::unique_ptr<FixBuffer> currentBuffer_; //当前buffer
std::unique_ptr<FixBuffer> nextBuffer_; //备用buffer
std::vector<std::unique_ptr<FixBuffer>> buffers_; //保存buffer的vector
std::thread acceptThread_; //后台接受数据的线程
std::mutex mutex_; //互斥变量
std::condition_variable_any condition_; //条件变量
Timestamp timestamp_; //时间戳
LogLevel currentLevel_; //当前日志等级
};
}
#endif异步日志类的实现
#include "asynLog.h"
#include "logFile.h"
#include "timestamp.h"
#include <stdio.h>
#include <string.h>
#include <memory>
#include "fixBuffer.h"
#include <mutex>
#include <condition_variable>
#include <functional>
#include <pthread.h>
using namespace netlib;
AsynLog::AsynLog(int rollSize)
:rollSize_(rollSize),
running_(true),
currentBuffer_(new FixBuffer()),
nextBuffer_(new FixBuffer()),
acceptThread_(std::bind(&AsynLog::threadFunc,this))
{
}
AsynLog::~AsynLog()
{
stop();
}
void AsynLog::setLevel(LogLevel level)
{
currentLevel_ = level;
}
bool AsynLog::aboveLevel(LogLevel level)
{
return level <= currentLevel_;
}
void AsynLog::append(char *logline,int len,LogLevel level)
{
if(aboveLevel(level)) //如果level超过所设等级
{
std::lock_guard<std::mutex> guard(mutex_);
//与时间以及线程id等字符串连接
std::string log1(logline); //日志内容
std::string log2(timestamp_.toStringTime());//获得时间戳的字符串
char log3[30];
snprintf(log3,sizeof(log3),"threadid[%lu]: ",pthread_self());//获得线程id的字符串
std::string log4(toStringForLevel(level)); //获得等级对应的字符串
log2 = log2 + log3 + log4 + log1;
writeBuffer(log2.c_str(),log2.size()); //写入buffer
}
}
void AsynLog::writeBuffer(const char *logline,int len)
{
if(currentBuffer_->writeableSize() >= len) //如果当前buffer空间足
{
currentBuffer_->append(logline,len);
}
else
{
buffers_.push_back(std::move(currentBuffer_)); //返回指针，自己变为空
if(nextBuffer_)
{
currentBuffer_ = std::move(nextBuffer_); //将nextBuffer_的控制权交给currentBuffer_
}
else
{
currentBuffer_.reset(new FixBuffer()); //申请一块新的buffer
}
currentBuffer_->append(logline,len);
condition_.notify_one(); //唤醒后台线程
}
}
std::string AsynLog::toStringForLevel(LogLevel level)
{
switch(level)
{
case LogLevel::OFF:
return std::string("OFF ");break;
case LogLevel::FATAL:
return std::string("FATAL ");break;
case LogLevel::ERROE:
return std::string("ERROE ");break;
case LogLevel::WARN:
return std::string("WARN ");break;
case LogLevel::INFO:
return std::string("INFO ");break;
case LogLevel::DEBUG:
return std::string("DEBUG ");break;
case LogLevel::ALL:
return std::string("ALL ");break;
default:return std::string("UNKNOWN ");
}
return NULL;
}
void AsynLog::stop(void)
{
if(running_)
{
running_ = false;
acceptThread_.join(); //等待后台进程退出
printf("日志系统已关闭\n");
}
}
void AsynLog::threadFunc(void)
{
std::unique_ptr<FixBuffer> newBuffer1(new FixBuffer);
std::unique_ptr<FixBuffer> newBuffer2(new FixBuffer);
std::vector<std::unique_ptr<FixBuffer>> buffersToWrite;
LogFile output(rollSize_);
buffersToWrite.reserve(16);
while(running_)
{
{
std::lock_guard<std::mutex> guard(mutex_); //临界区加锁
if(buffers_.empty()) //如果buffers_为空
{
condition_.wait_for(mutex_,std::chrono::seconds(3));
}
buffers_.push_back(std::move(currentBuffer_));
currentBuffer_ = std::move(newBuffer1);
buffersToWrite.swap(buffers_); //交换俩个容器
if(!nextBuffer_)
{
nextBuffer_ = std::move(newBuffer2);
}
}
assert(!buffersToWrite.empty());
if(buffersToWrite.size() > 25)
{
//日志异常
}
//将buffer中的内容写进文件中
for(int i = 0; i < buffersToWrite.size(); i++)
{
output.append(buffersToWrite[i]->getReadPeek(),buffersToWrite[i]->readableSize());
}
if(buffersToWrite.size() > 2)
{
buffersToWrite.resize(2);
}
if(!newBuffer1)
{
assert(!buffersToWrite.empty());
newBuffer1 = std::move(buffersToWrite[0]);
newBuffer1->resetBuffer(); //重置buffer
}
if(!newBuffer2)
{
assert(!buffersToWrite.empty());
newBuffer2 = std::move(buffersToWrite[1]);
newBuffer2->resetBuffer();
}
buffersToWrite.clear();
}
}测试代码
#include<iostream>
#include "asynLog.h"
#include <stdio.h>
#include <unistd.h>
#include <string.h>
#include <thread>
netlib::AsynLog log(1024*1024*1024);
void func(void)
{
char s[100] = "hello\n";
log.setLevel(netlib::LogLevel::ALL);
while(true)
{
log.append(s,strlen(s),netlib::LogLevel::INFO);
}
}
int main(int argc,char **argv)
{
std::thread t1(func);
std::thread t2(func);
std::thread t3(func);
std::thread t4(func);
t1.join();
t2.join();
t3.join();
t4.join();
return 0;
}github:https://github.com/Miaoshuai/LogLibrary/tree/master/LogLibrary
写在日志的功能还在完善中，希望大家能给出意见!