Merge "Upgrade ELK to 6.1.3"

diff --cc extra/docker/elk/docker-compose.yml
index 388c318,2f1ce24..3b5571e
--- 1/extra/docker/elk/docker-compose.yml
--- 2/extra/docker/elk/docker-compose.yml
+++ b/extra/docker/elk/docker-compose.yml
@@@ -9,12 -9,15 +9,16 @@@ services
        es_net:
          aliases:
            - elasticsearch
+     environment:
+       - cluster.name=docker-cluster
+       - bootstrap.memory_lock=false
+       - "ES_JAVA_OPTS=-Xms512m -Xmx512m"
  
    logstash:
-     image: logstash
+     image: docker.elastic.co/logstash/logstash:6.1.3
      volumes:
        - ./logstash-conf:/config-dir
 +      - ./logstash-input:/log-input
      command: logstash -f /config-dir/logstash.conf
      depends_on:
        - elasticsearch

diff --cc extra/docker/elk/logstash-conf/logstash.conf
Simple merge