项目日志——Log4cpp

• 开源的C++类库Log4cpp提供了很多功能，帮助我们的应用程序更方便地记录日志。

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安装与构建

• Log4cpp官网——http://log4cpp.sourceforge.net/

wget https://nchc.dl.sourceforge.net/project/log4cpp/log4cpp1.1.x%20%28new%29/log4cpp-1.1/log4cpp-1.1.3.tar.gz
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tar zxvf log4cpp-1.1.3.tar.gz
cd log4cpp
# root用户
./configure --prefix=执行路径  
# 示例   
# ./configure --prefix=/home/xuanxuan/share_bike/third/lib/log4cpp
make
make install
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使用

• 包含头文件

#include 
#include 
#include 
#include 
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• 初始化日志输出的目的地

示例1:输出到标准输出std::cout

log4cpp::Appender *appender = new log4cpp::OstreamAppender("root", &std::cout);
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示例2:输出到log文件

log4cpp::Appender *appender = new log4cpp::FileAppender("root", "test.log");
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输出方式如下:

log4cpp::FileAppender // 输出到文件
log4cpp::RollingFileAppender // 输出到回卷文件，即当文件到达某个大小后回卷
log4cpp::OstreamAppender // 输出到一个ostream类
log4cpp::RemoteSyslogAppender // 输出到远程syslog服务器
log4cpp::StringQueueAppender // 内存队列
log4cpp::SyslogAppender // 本地syslog
log4cpp::Win32DebugAppender // 发送到缺省系统调试器
log4cpp::NTEventLogAppender // 发送到win 事件日志
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注意：

实际上日志输出到终端或文件中是很慢的，可能会引起IO中断,所以我们可以先输出到内存中(StringQueueAppender),然后在输出到其它地方，这样效率较高。

• 设置日志输出格式

log4cpp::PatternLayout *patternLayout = new log4cpp::PatternLayout();
patternLayout->setConversionPattern("%d [%p] - %m%n");
appender->setLayout(patternLayout);
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日志输出格式控制如下:

log4cpp::PatternLayout Class Reference

%%%% - a single percent sign
%c - the category
%d - the date
Date format: The date format character may be followed by a date format specifier enclosed between braces. For example, %d{%H:%M:%S,%l} or %d{%d %m %Y %H:%M:%S,%l}. If no date format specifier is given then the following format is used: "Wed Jan 02 02:03:55 1980". The date format specifier admits the same syntax as the ANSI C function strftime, with 1 addition. The addition is the specifier %l for milliseconds, padded with zeros to make 3 digits.
%m - the message
%n - the platform specific line separator
%p - the priority
%r - milliseconds since this layout was created.
%R - seconds since Jan 1, 1970
%u - clock ticks since process start
%x - the NDC
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• 设置输出类别和日志优先级

log4cpp::Category &root = log4cpp::Category::getRoot();
root.setPriority(log4cpp::Priority::NOTICE);
root.addAppender(appender);
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日志的级别如下:

NOTSET < DEBUG < INFO < NOTICE < WARN < ERROR < CRIT < ALERT < FATAL = EMERG。
低于该级别的日志不会被记录。

• 定义宏来减少代码量

#define LOG(__level) log4cpp::Category::getRoot() << log4cpp::Priority::__level << __FILE__ << " " << __LINE__ << ": "
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使用:

LOG(DEBUG)<<"DEBUG.";
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---

测试

什么是单例？

• 程序中仅有一个的对象。

配置文件:log.conf

#定义Root category的属性
log4cpp.rootCategory=DEBUG, RootLog

#定义RootLog属性
log4cpp.appender.RootLog=RollingFileAppender
log4cpp.appender.RootLog.layout=PatternLayout

log4cpp.appender.RootLog.layout.ConversionPattern=%d{%m-%d %H:%M:%S %l} [%t][%p]%m%n
log4cpp.appender.RootLog.fileName=/var/log/share_bike.log
log4cpp.appender.RootLog.maxFileSize=268435456 #256MB
log4cpp.appender.RootLog.fileNamePattern=share_bike_%i.log
log4cpp.appender.RootLog.maxBackupIndex=256
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• 封装为一个类

Logger.h

#ifndef DISTRIBUTED_LOGGER_H_
#define DISTRIBUTED_LOGGER_H_

#include 
#include 


class Logger{
public:
    bool init(const std::string& log_conf_file);

    static Logger* instance(){//返回单例——全局唯一对象
        return &instance_;
    }

    log4cpp::Category* GetHandle(){
        return category_;
    }
    
protected:
    static Logger instance_;
    log4cpp::Category* category_;
};

#define LOG_INFO Logger::instance()->GetHandle()->info
#define LOG_DEBUG Logger::instance()->GetHandle()->debug
#define LOG_ERROR Logger::instance()->GetHandle()->error
#define LOG_WARN Logger::instance()->GetHandle()->warn

#endif
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Logger.cpp

#include "Logger.h"

#include 
#include 
#include 
#include 
#include 
#include 

Logger Logger::instance_;

bool Logger::init(const std::string& log_conf_file){
    try{
        log4cpp::PropertyConfigurator::configure(log_conf_file);

    }catch(log4cpp::ConfigureFailure& f){
        std::cerr << " load log config file " << log_conf_file.c_str() << " failed with result : " << f.what()<< std::endl;
        return false;
    }
    category_ = &log4cpp::Category::getRoot();
    return true;
}
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• 测试

main.cpp

#include "iniconfig.h" //注意路径，会在CMake中进行调整
#include "configdef.h"
#include "Logger.h"

int main(int argc,char** argv){

    if(argc != 3){//缺少参数
        printf("Please input shbk  !\n");
        return -1;
    }

    if(!Logger::instance()->init(std::string(argv[2]))){
        fprintf(stderr,"init log module failed.\n");
        return -2;
    }


    Iniconfig config;
    if(!config.loadfile(std::string(argv[1]))){
        //printf("load %s failed.\n",argv[1]);
        LOG_ERROR("load %s failed.",argv[1]);
        return -3;
    }

    //测试是否读取成功
    st_env_config conf_args = config.getconfig();
    LOG_INFO("[database]ip:%s\n [database]port:%d\n [database]user:%s\n [database]pwd:%s\n [database]db:%s\n [server]port:%d\n ",
                conf_args.db_ip.c_str(),
                conf_args.db_port,
                conf_args.db_user.c_str(),
                conf_args.db_pwd.c_str(),
                conf_args.db_name.c_str(),
                conf_args.svr_port);
    return 0;
}
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**注意链接库:**下面为示例，请根据自身情况调整。

TARGET_LINK_LIBRARIES(common log4cpp)
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TARGET_LINK_LIBRARIES(share_bike pthread)
TARGET_LINK_LIBRARIES(${PROJECT_NAME} liblog4cpp.a)
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执行:

./share_bike ../conf/share_bike.ini ../conf/log.conf
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查看:

在log.conf中。/var/log/share_bike.log为保存路径。

log4cpp.appender.RootLog.fileName=/var/log/share_bike.log
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