Add support for TLS settings

[slauger]

The rubygem gelf library supports ssl since it's version 3.0.0. This PR adds new SSL options to logstash-output-gelf. This is pretty much a reimplementation of #28.

Parameters

• ssl (boolean)
• ssl_certificate_authorities (string)
• ssl_certificate (string)
• ssl_key (string)
• ssl_verify_mode ([none, peer, force_peer])

Currently there is no option for ssl_ciphers as the gelf library dosen't have any kind of cipherlist option.

Please review and let me know if any changes are necessary.

[slauger]

Hi, i just signed the CLA. Let me know if any further changes are necessary.

[slauger]

Any update or feedback? Is there anything i can do to increase the chance of merging?

[KurzweilTV]

Is anyone available to look at this request? Having this support for the gelf output would be highly valuable.

[slauger]

I'm going to close this because i'm no longer working on this. Because of the poor support we decided to move away from logstash-output-gelf. We also had some performance issues with the GELF output. If anyone is interested feel free to "fork my fork".

The main reason for this was to get our stuff from Logstash into our Graylog instance. We finally resolved this by putting a RabbitMQ instance between Logstash and Graylog (and using logstash-output-rabbitmq).