# Duplicate messages with logstash and log4net RollingFileAppender

**URL:** <https://discuss.elastic.co/t/duplicate-messages-with-logstash-and-log4net-rollingfileappender/349932>\
**Category:** Logstash\
**Created:** [December 26, 2023, 8:50am UTC](https://discuss.elastic.co/t/duplicate-messages-with-logstash-and-log4net-rollingfileappender/349932 "2023-12-26T08:50:32Z")\
**Posts on this page:** 3\
**Page:** 1

<div class="post-metadata">

**Author:** ![pumiki](https://avatars.discourse-cdn.com/v4/letter/p/b5ac83/32.png) [@pumiki](https://discuss.elastic.co/u/pumiki)\
**Post date:** [December 26, 2023, 8:50am UTC](https://discuss.elastic.co/t/duplicate-messages-with-logstash-and-log4net-rollingfileappender/349932/1 "2023-12-26T08:50:32Z")

</div>

Hello,  
My app writes events using log4net with rolling file appender.  
I get messages duplicated in the file gerenated by logstash.  
I found the issue mentioned also [here](https://discuss.elastic.co/t/logstash-file-input-plugin-duplicate-events-after-log-file-rollover/207750)  
However, I am not sure about the solution.  
Could any one assist ?

cam logstash work with log4net RoolingFileAppender ?  
what is the right way to configure logstash file input plugin in that way ?

---

<div class="post-metadata">

**Author:** ![pumiki](https://avatars.discourse-cdn.com/v4/letter/p/b5ac83/32.png) [@pumiki](https://discuss.elastic.co/u/pumiki)\
**Post date:** [December 26, 2023, 10:53am UTC](https://discuss.elastic.co/t/duplicate-messages-with-logstash-and-log4net-rollingfileappender/349932/2 "2023-12-26T10:53:46Z")

</div>

Adding the log4et appender:

```auto

  <appender name="RollingLogFileAppender" type="log4net.Appender.RollingFileAppender">
    <file value=".\App.log" />
    <appendToFile value="true" /> <!-- true-->
    <rollingStyle value="Size" />
    <maxSizeRollBackups value="2" /> <!-- 100-->
    <maximumFileSize value="1Mb" /> 
    <!-- 10Mb-->
    <staticLogFileName value="true"/>
    <preserveLogFileNameExtension value="true"/>
    <layout type="log4net.Layout.XmlLayout" />
    <filter type="log4net.Filter.levelRangeFilter">
      <levelMin value="INFO" />
    </filter>
  </appender>

adding logstash config

``
input
{
  	file
  	{
		path => "./App.log"
		codec => multiline 
		{
			pattern => "^<log4net:event "
			negate => true
			what => previous
		}
	}
}
filter 
{
	xml 
	{
		source => "message"	
		remove_namespaces => true
		force_array => "false"
		xpath => 
		{
			"/event/message/text()" => "LogMessage"
					
		}
		store_xml => false
  	}
}
output
{
     csv { 
            fields => ["LogMessage"]
            path => "c:\dockers\logstash\logstash-8.11.2\config\demo099b_xml_output.csv"
          }   

}
```

---

<div class="post-metadata">

**Author:** ![system](https://us1.discourse-cdn.com/elastic/original/3X/1/a/1ac57faf039f6b580b3f104ef42a2a89e41014de.png) [@system](https://discuss.elastic.co/u/system)\
**Post date:** [January 23, 2024, 10:54am UTC](https://discuss.elastic.co/t/duplicate-messages-with-logstash-and-log4net-rollingfileappender/349932/3 "2024-01-23T10:54:11Z")

</div>

This topic was automatically closed 28 days after the last reply. New replies are no longer allowed.