title: LogstashTcpSocketAppender is not sending logs to Logstash
body: <p>I am using Docker ELK stack with my Spring Boot application. All three components are up and running at <a href="http://192.168.99.100:5601/" rel="nofollow noreferrer">http://192.168.99.100:5601/</a>, <a href="http://192.168.99.100:9200/" rel="nofollow noreferrer">http://192.168.99.100:9200/</a> and 192.168.99.100:5000 respectively.</p>
  
  <p>My logback-spring.xml looks like:</p>
  
  <pre><code>&lt;?xml version="1.0" encoding="UTF-8"?&gt;
  &lt;configuration&gt;
  &lt;include resource="org/springframework/boot/logging/logback/base.xml"/&gt;
  &lt;appender name="stash" class="net.logstash.logback.appender.LogstashTcpSocketAppender"&gt;
      &lt;keepAliveDuration&gt;5 minutes&lt;/keepAliveDuration&gt;
      &lt;reconnectionDelay&gt;10 second&lt;/reconnectionDelay&gt;
      &lt;waitStrategyType&gt;sleeping&lt;/waitStrategyType&gt;
      &lt;destination&gt;192.168.99.100:5000&lt;/destination&gt;
      &lt;encoder class="net.logstash.logback.encoder.LoggingEventCompositeJsonEncoder"&gt;
          &lt;providers&gt;
              &lt;mdc/&gt; &lt;!-- MDC variables on the Thread will be written as JSON fields--&gt;
              &lt;context/&gt; &lt;!--Outputs entries from logback's context --&gt;
              &lt;logLevel/&gt;
              &lt;loggerName/&gt;
              &lt;pattern&gt;
                      {
                      "timestamp": "%date{\"yyyy-MM-dd'T'HH:mm:ss,SSSXXX\", UTC}",
                      "level": "%level",
                      "logger": "%logger",
                      "message": "%message",
                      "logstashMarkers": "%marker"
                      }
                  &lt;/pattern&gt;
              &lt;threadName/&gt;
              &lt;message/&gt;
              &lt;logstashMarkers/&gt; &lt;!-- Useful so we can add extra information for specific log lines as Markers--&gt;
              &lt;arguments/&gt; &lt;!--or through StructuredArguments--&gt;
             &lt;stackTrace&gt;
                  &lt;fieldName&gt;stackTrace&lt;/fieldName&gt;
                  &lt;throwableConverter class="net.logstash.logback.stacktrace.ShortenedThrowableConverter"&gt;
                      &lt;exclude&gt;net\.sf\.cglib\..*&lt;/exclude&gt;
                      &lt;maxDepthPerThrowable&gt;30&lt;/maxDepthPerThrowable&gt;
                      &lt;rootCauseFirst&gt;true&lt;/rootCauseFirst&gt;
                  &lt;/throwableConverter&gt;
              &lt;/stackTrace&gt;
          &lt;/providers&gt;
      &lt;/encoder&gt;
  &lt;/appender&gt;
  
  &lt;root level="INFO"&gt;
      &lt;appender-ref ref="stash"/&gt;
  &lt;/root&gt;
  </code></pre>
  
  <p></p>
  
  <p><strong>The issue is that I am not able to see my logs in the Kibana and my doubt is that LogstashTcpSocketAppender is not sending logs to Logstash. Is there a way by which I can validate whether LogstashTcpSocketAppender is sending logs to Logstash or not?</strong></p>