This commit updates the Zen Discovery documentation to explain which
nodes partcipate in master election (by default) as well as the
configuration parameters for controlling this.
Closes#12727
During master election each node pings in order to discover other nodes and validate the liveness of existing nodes. Based on this information the node either discovers an existing master or, if enough nodes are found (based on `discovery.zen.minimum_master_nodes>>) a new master will be elected.
Currently, the node that is elected as master will currently update it the cluster state to indicate the result of the election. Other nodes will submit a join request to the newly elected master node. Instead of immediately processing the election result, the elected master
node should wait for the incoming joins from other nodes, thus validating the elections result is properly applied. As soon as enough nodes have sent their joins request (based on the `minimum_master_nodes` settings) the cluster state is modified.
Note that if `minimum_master_nodes` is not set, this change has no effect.
Closes#12161
When a node sends a join request to the master, only send back the response after it has been added to the master cluster state and published.
This will fix the rare cases where today, a join request can return, and the master, since its under load, have not yet added the node to its cluster state, and the node that joined will start a fault detect against the master, failing since its not part of the cluster state.
Since now the join request is longer, also increase the join request timeout default.
closes#6480
Using ping.timeout, which defaults to 3s, to use as a timeout value on the join request a node makes to the master once its discovered can be too small, specifically when there is a large cluster state involved (and by definition, all the buffers and such on the nio layer will be "cold"). Introduce a dedicated join.timeout setting, that by default is 10x the ping.timeout (so 30s by default).
closes#6342
Jason Tedor
Boaz Leskes
javanna
Clinton Gormley
Martijn van Groningen
Christian Verkerk
Simon Willnauer
Shay Banon
David Pilato
Lee Hinman