Add upstream quote about elastic 5.x vm.max_map_count check

[yosifkit]

Related to docker-library/elasticsearch#98.

[tianon]

Nice 👍

[yosifkit]

Reading further in elastic/elasticsearch#4978, I found this:

You can set http.host independently of transport.host (network.host sets both); the bootstrap checks are only enforced if a node is able to form a cluster with other instances not on localhost
- elastic/elasticsearch#4978 (comment)

So maybe, instead we change our default provided config to not set network.host and instead just http.host and print a warning in the logs and here in the docs to let users know how to set it up for clustering.

[yosifkit]

So, it will work with a smaller vm.max_map_count on the host; the only drawback is that it won't be able to cluster with other nodes, since that part is now only on localhost of the container.

$ sudo sysctl -w vm.max_map_count=262144
$ docker run -it --rm elacticsearch:5
...
[2016-12-20T00:47:34,773][INFO ][o.e.b.BootstrapCheck     ] [vvWlFNU] bound or publishing to a non-loopback or non-link-local address, enforcing bootstrap checks
... works (no warning or error)
$ sudo sysctl -w vm.max_map_count=262000
$ docker run -it --rm elacticsearch:5
...
[2016-12-20T00:32:39,125][INFO ][o.e.b.BootstrapCheck     ] [YoNYX3Z] bound or publishing to a non-loopback or non-link-local address, enforcing bootstrap checks
ERROR: bootstrap checks failed
max virtual memory areas vm.max_map_count [262000] is too low, increase to at least [262144]
... fails
$ # build new elasticsearch:5 with 
diff --git a/5/config/elasticsearch.yml b/5/config/elasticsearch.yml
-network.host: 0.0.0.0
+http.host: 0.0.0.0
$ # vm.max_map_count still set to 262000
$ docker run -it --rm new-elacticsearch:5
...
[2016-12-20T00:36:44,447][INFO ][o.e.t.TransportService   ] [UdTHcL7] publish_address {127.0.0.1:9300}, bound_addresses {[::1]:9300}, {127.0.0.1:9300}
[2016-12-20T00:36:44,452][WARN ][o.e.b.BootstrapCheck     ] [UdTHcL7] max virtual memory areas vm.max_map_count [262000] is too low, increase to at least [262144]
... SUCCESS! (just a warning)

[tianon]

+1 sounds great! That's exactly what I wanted when I set this config in the first place; mind commenting on that other issue and opening a PR? 👍