When reading the [rolling upgrade process](http://www.elasticsearch.org/guide/en/elasticsearch/reference/current/setup-upgrade.html#rolling-upgrades), you can see that we wrote:
* disable allocation
* upgrade node1
* upgrade node2
* upgrade node3
* ...
* enable allocation
That won't work as after a node has been removed and restarted, no shard will be allocated anymore.
So closing node2 and remaining nodes, won't help to serve index and search request anymore.
We should write:
* disable allocation
* upgrade node1
* enable allocation
* wait for shards being recovered on node1
* disable allocation
* upgrade node2
* enable allocation
* wait for shards being recovered on node2
* disable allocation
* upgrade node3
* enable allocation
* wait for shards being recovered on node3
* disable allocation
* ...
* enable allocation
I think this documentation update should go in 1.3, 1.4, 1.x and master branches.
Closes#8218Closes#7973.
David Pilato
corochoone
Martijn van Groningen
Sean Gallagher