title: Why doesn't Logstash consume logs from gelf?
body: <p>I'm trying to set up an interaction between running Docker container's logs and Logstash.</p>
  
  <p>I run my Docker container with the following command:</p>
  
  <pre><code>docker run --log-driver gelf --log-opt gelf-address=udp://127.0.0.1:12201 nfrankel/simplelog:1
  </code></pre>
  
  <p>and the Logstash <code>config.json</code> is:</p>
  
  <pre><code>input {
    gelf {}
  }
  
  output {
    elasticsearch {
      hosts =&gt; ["http://localhost:9200"]
    }
    stdout {}
  }
  </code></pre>
  
  <p>Logstash logs are fine, I see </p>
  
  <pre><code>New Elasticsearch output {:class=&gt;"LogStash::Outputs::ElasticSearch", :hosts=&gt;["http://localhost:9200"]}
  Starting gelf listener (udp) ... {:address=&gt;"0.0.0.0:12201"}
  Successfully started Logstash API endpoint {:port=&gt;9600}
  </code></pre>
  
  <p>Nevertheless, it doesn't work. I don't see either logs in Logstash console or that Elasticsearch index is created.</p>
  
  <p>Could you help me to resolve my issue?</p>
  
  <p>Worth to mention that the running Docker container produces logs and I see them in a Cygwin from where I launched it.</p>