# Logstash not generating any output: "Class path contains multiple SLF4J bindings." error

**URL:** <https://discuss.elastic.co/t/logstash-not-generating-any-output-class-path-contains-multiple-slf4j-bindings-error/254262>\
**Category:** Logstash\
**Created:** [November 4, 2020, 11:34am UTC](https://discuss.elastic.co/t/logstash-not-generating-any-output-class-path-contains-multiple-slf4j-bindings-error/254262 "2020-11-04T11:34:17Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![Silvia\_Koleva](https://sea2.discourse-cdn.com/elastic/user_avatar/discuss.elastic.co/silvia_koleva/32/78391_2.png) [@Silvia\_Koleva](https://discuss.elastic.co/u/Silvia_Koleva)\
**Post date:** [November 4, 2020, 11:34am UTC](https://discuss.elastic.co/t/logstash-not-generating-any-output-class-path-contains-multiple-slf4j-bindings-error/254262/1 "2020-11-04T11:34:17Z")

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Hello,  
I am trying to configure Logstash to collect data from filebeat, where itgets some SharePoint ULS logs and then push them to Elasticsearch with applying some filters. The issue I have is when I run the logstash service it generates the following messages when I view the logs and it basically does not write anything to Elasticsearch:  
WARNING: An illegal reflective access operation has occurred  
WARNING: Illegal reflective access by com.headius.backport9.modules.Modules (file:/.../lib/jars/jruby-complete-9.2.11.1.jar) to field java.io.Console.cs  
WARNING: Please consider reporting this to the maintainers of com.headius.backport9.modules.Modules  
WARNING: Use --illegal-access=warn to enable warnings of further illegal reflective access operations  
WARNING: All illegal access operations will be denied in a future release  
SLF4J: Class path contains multiple SLF4J bindings.

Then it loops again and again the same message appears.  
Could you please help me to better identify the issue?

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<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:** [December 2, 2020, 11:34am UTC](https://discuss.elastic.co/t/logstash-not-generating-any-output-class-path-contains-multiple-slf4j-bindings-error/254262/2 "2020-12-02T11:34:19Z")

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