Work with Logstash 5.x versions. Please use logstash-v6x.py if you are using logstash v6 and rename it logstash.py to match example. A new template for Zabbix 3.4 is also needed.

From pip:

pip install protobix

Import Template in Zabbix with Template_Logstash.xml if you are using Zabbix 3.4. If you are using Zabbix 3.2, you can use Template_Logstash-32.xml.

Put logstash.py in UserParameter in zabbix agent configuration.

UserParameter=logstash.check,/usr/local/bin/logstash.py --update-items UserParameter=logstash.discovery,/usr/local/bin/logstash.py --discovery

Restart zabbix agent.

Link Template to host in Zabbix.

Enjoy!