AI interviewer: use Log4Net in Asp.Net (3)

AI interviewer: use Log4Net in Asp.Net (3)

When interviews involve questions about using the log4net logging framework, they usually focus on how to integrate and use log4net in .NET or .NET Core applications. Here are some interview questions about log4net, with corresponding answers, examples and code:

11. How to implement asynchronous recording of log information in log4net?

Answer: Log4net can be used AsyncAppenderto record log information asynchronously. AsyncAppenderLogging is handled in a background thread to avoid blocking the main thread.

Case and code: Add in the configuration file of log4net AsyncAppenderto realize asynchronous recording of log information:

<log4net>
    <appender name="AsyncAppender" type="log4net.Async.AsyncAppender">
        <appender-ref ref="FileAppender" />
    </appender>

    <root>
        <level value="INFO" />
        <appender-ref ref="AsyncAppender" />
    </root>
</log4net>

12. How to realize the email sending of log information in log4net?

Answer: You can use log4net SmtpAppenderto send emails of log information. You need to configure the SMTP server information, recipient address, etc.

Case and code: Add in the configuration file of log4net SmtpAppenderto realize the mail sending of log information:

<log4net>
    <appender name="SmtpAppender" type="log4net.Appender.SmtpAppender">
        <to value="[email protected]" />
        <from value="[email protected]" />
        <subject value="Log4net Error" />
        <smtpHost value="smtp.example.com" />
        <bufferSize value="512" />
        <lossy value="true" />
        <evaluator type="log4net.Core.LevelEvaluator">
            <threshold value="ERROR" />
        </evaluator>
        <layout type="log4net.Layout.PatternLayout">
            <conversionPattern value="%date [%thread] %-5level %logger - %message%newline" />
        </layout>
    </appender>

    <root>
        <level value="ERROR" />
        <appender-ref ref="SmtpAppender" />
    </root>
</log4net>

13. How does log4net record the context data (Context Data) of log information?

ANSWER: You can use log4net's ThreadContext.Propertiesor LogicalThreadContext.Propertiesto log the context data of the log information. This can output some additional associated information in the log, such as user ID, request ID, etc.

ThreadContext.PropertiesExample and code: Use context data for logging information in code :

// 在某个操作中添加上下文数据
ThreadContext.Properties["UserId"] = 12345;
ThreadContext.Properties["RequestId"] = Guid.NewGuid().ToString();

// 记录日志
_logger.Info("Some log message");

14. How to use log4net for dynamic configuration of log information?

Answer: You can use the log4net XmlConfigurator.ConfigureAndWtchmethod to achieve dynamic configuration. This way log4net automatically reloads the configuration when the configuration file changes.

Case and code: Program.csUse XmlConfigurator.ConfigureAndWatchthe method in the file of the .NET Core Web API project:

class Program
{
    
    
    static void Main(string[] args)
    {
    
    
        var logRepository = LogManager.GetRepository(Assembly.GetEntryAssembly());
        XmlConfigurator.ConfigureAndWatch(logRepository, new FileInfo("log4net.config"));

        CreateHostBuilder(args).Build().Run();
    }

    // 其他代码
    // ...
}

15. How does log4net implement dynamic switching of log information, such as outputting logs separately in the development environment and the production environment?

Answer: Dynamic switching of log information can be achieved by using conditions in the log4net configuration file. Classes can be used log4net.Util.SystemInfoto determine the current operating environment and output different log configurations based on conditions.

Case and code: Use conditions in the log4net configuration file to output different log configurations according to the operating environment:

<log4net>
    <!-- 开发环境日志配置 -->
    <appender name="DevFileAppender" type="log4net.Appender.FileAppender">
        <file value="logs/development.log" />
        <!-- ... 其他配置 ... -->
    </appender>

    <!-- 生产环境日志配置 -->
    <appender name="ProdFileAppender" type="log4net.Appender.FileAppender">
        <file value="logs/production.log" />
        <!-- ... 其他配置 ... -->
    </appender>

    <!-- 设置Root Logger使用不同的Appender -->
    <root>
        <level value="INFO" />
        <!-- 根据运行环境使用不同的Appender -->
        <appender-ref ref="DevFileAppender" />
        <!-- <appender-ref ref="ProdFileAppender" /> -->
    </root>
</log4net>