Logstash 5.6.x to 6.1.0 and ES template update

[phr0gz]

Hello,

Here is the list of changes/recommendations (I hope I don't miss anything):

1. Logstash:
   ES output plugin will change the document_type from logs to doc

2. ElasticSearch:
   Indices created in Elasticsearch 6.0.0 or later may only contain a single mapping type.
   default mapping will be removed on ES 7 (so it's better to not use this one).

3. Concerning the upgrade:
   Recommended upgrade order is Elasticsearch --> Kibana --> Logstash

Actual infrastructure:

1. Logstash 5.6 is inserting data to Elasticsearch 5.3 and Kibana 5.6 is used to view the data.

2. Logstash is creating different indexes every days with index => "logstash-index1-%{+YYYY.MM.dd}" (using custom templates stored in Elasticsearch) in Elasticsearch.

3. For the predefined templates I use the following mapping:
   ... "mappings" : { "Log" : { "dynamic" : false, "_source" : { "enabled" : true }, "properties":{ ....

Upgrade to ELK 6
I plan to update ELK stack to 6.x (with the shortest downtime possible), and I've few questions about how to do it:

1. Before starting the upgrade can I update the mapping of the templates to:
   ... "mappings" : { "doc" : { "dynamic" : false, "_source" : { "enabled" : true }, "properties":{ ...

Then do I need to add the document_type value and set it to doc?
And few days later I will update the ELK stack in the recommended order.
Can it work in that way?

2. If I upgrade ES and Kibana first, can I let Logstash in the 5.6 or will I have issues when the new indexes will be created the day after?

3. Or must I stop Logstash before the daily indexes creation, and then:
   a/ Upgrade the ES templates as mentioned previously.
   b/ Upgrade ES --> Kibana --> Logstash
   c/ Start ES --> Kibana --> Logstash

Thanks.