title: Logstash: forwardings logs via proxy to logz.io
body: <p>I want to ship stdout from a running application to logz.io using logstash. Application and logstash are both docker images managed by docker-compose, which does the setup (pull images, network_mode, logging driver etc.). Logstash input is handled via gelf-input-plugin. The shipping to logz.io is handled via tcp-output-plugin.</p>
  
  <p>logstash.conf:</p>
  
  <pre><code>input { gelf {
              type =&gt; docker
              port =&gt; 12201 } }
  
  filter { mutate { add_field =&gt; { "token" =&gt; "${LOGZIOTOKEN}" } } }
  
  output { tcp {
              host =&gt; "listener.logz.io"
              port =&gt; 5050
              codec =&gt; json_lines } }
  </code></pre>
  
  <p>excerpt from docker-compose.yml:</p>
  
  <pre><code>  application:
    ...
   logging:
     driver: "gelf"
    options:
      gelf-address: "udp://0.0.0.0:12201"
  </code></pre>
  
  <p>This works as expected. </p>
  
  <p>Now there is a TCP proxy server I need to use, to ship the logs from the host (running the logstash instance) to logz.io. Unfortunately I did not find a proxy extension for logstashs tcp-output-plugin. Does anyone has a suggestion for this issue?</p>