I currently have the following setup:
Logstash - Collector (1.5) -> Redis (3.0) -> Logstash - Indexer (1.5) -> Elasticsearch (1.5.2) <- Kibana (4.1)
I'm looking to upgrade all to the latest version, however as we are unable to have virtually any downtime with this setup I'm not sure the best way to get around it.
Can Elasticsearch be upgraded to the latest version at the same time our Logstash Indexers and Kibana whilst leaving the Logstash Collectors on the v1,5? Redis has plenty of RAM to store a large buffer of logs to hold out until the Indexers came back online.
Assuming we can, I can then upgrade the Collectors at a quiet time to minimise data loss.