# 2013-10-17  Log4perl多个Appender重复输出日志的问题解决办法

Perl开发中会经常用到Log4perl来输出日志，例如有类似如下配置：

```
log4perl.rootLogger = DEBUG, Screen
log4perl.logger.Utils = DEBUG, Screen

log4perl.appender.Logfile = Log::Log4perl::Appender::File
log4perl.appender.Logfile.filename = test.log
log4perl.appender.Logfile.layout = Log::Log4perl::Layout::PatternLayout
log4perl.appender.Logfile.layout.ConversionPattern = %r %F %L %m%n

log4perl.appender.Screen = Log::Log4perl::Appender::Screen
log4perl.appender.Screen.stderr = 1
log4perl.appender.Screen.layout = Log::Log4perl::Layout::PatternLayout
log4perl.appender.Screen.layout.ConversionPattern = %M | %m%n
```

结果发现Utils中的消息，一次debug调用会输出两条同样的消息。Google一查发现还很常见，老祖宗Log4j下面也有类似的问题。作者在[FAQ中](http://log4perl.sourceforge.net/releases/Log-Log4perl/docs/html/Log/Log4perl/FAQ.html#a6c81)提到了这个问题，解决办法除了与Log4j类似的解决方案之外，Log4perl还有一个简单的办法，只要在配置加入一行

```
log4perl.oneMessagePerAppender = 1 
```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://blog.log4think.com/log4perl-duplicate-message.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.