title: Mosquitto: Outgoing messages are being dropped
body: <p>First, I'll start by telling that this question is a refinement of <a href="https://stackoverflow.com/q/49057771/">Mosquitto not propagating messages to AWS IoT using bridge configuration</a>, so lots of context and logs could be found on that question too, but I decided to start a new one as I guess I found a real symptom of the actual problem, which I prefer to handle it alone to avoid confusion with other possible issues:</p>
  
  <p>Mosquitto (<code>/var/log/mosquitto/mosqutto.log</code>) log files were actually disabled and, the only available logs where from <code>/var/log/syslog</code> but, when we enabled them, and issued a <code>cat mosquitto.log|grep bridge</code>, some relevant messages appeared:</p>
  
  <p>1.- <code>Bridge local.bridgeawsiot doing local SUBSCRIBE on topic #</code></p>
  
  <p>Which tells that all topic are being bridged</p>
  
  <p>2.- <code>Connecting bridge awsiot (myEndpoint.iot.us-east-1.amazonaws.com:8883)</code></p>
  
  <p>Which tells that it's using the correct endpoint</p>
  
  <p>3.-  <code>Outgoing messages are being dropped for client local.bridgeawsiot.</code></p>
  
  <p>Which worries me a lot, as I don't really know why is that happening, but seems like a clear symptom of the problem, but after a few searches I found:</p>
  
  <p>"The message "Outgoing messages are being dropped" is shown when the internal message queue become full.", so I guess messages are just being enqueued but not actually being sent to AWS IoT.</p>
  
  <p><strong>So my questions are:</strong> </p>
  
  <ol>
  <li>Why are these messages are being dropped?</li>
  <li>If they are being dropped because queue is full, then why queued messages are not being sent to the bridged endpoint?</li>
  </ol>
  
  <p><strong>Relevant info:</strong></p>
  
  <pre><code>Version: 1.4.14-0mosquitto1~jessie2
  OS: Debian GNU/Linux 9.1 (stretch)
  </code></pre>