Plugin silently discards undelivered messages

[jsmucr]

The gelf.rb dependency does not properly check for connection breakdown and discards every first message that it tries to send to server that just terminated the connection.

• Version: 3.1.4, gelf-3.0.0
• Operating System: CentOS 7
• Steps to Reproduce:
  1. Create a numbered messages generator
  2. Start a dummy Netcat server listening on (i.e.) 12201/tcp
  3. Send the generated messages to the Netcat server via the GELF output. All messages will be delivered.
  4. Restart the Netcat server.
  5. Send the generated messages again. The first message won't be delivered.

I've already posted a PR here: graylog-labs/gelf-rb#70
I've discovered this issue with the TCP output plugin as well, yet with one difference: The message got lost only if the server sent a random content back prior to the connection breakdown.

[jsmucr]

The gelf-rb PR has been merged.