76 lines
3.5 KiB
Plaintext
76 lines
3.5 KiB
Plaintext
[[discovery-settings]]
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=== Important discovery and cluster formation settings
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++++
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<titleabbrev>Discovery and cluster formation settings</titleabbrev>
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++++
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There are two important discovery and cluster formation settings that should be
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configured before going to production so that nodes in the cluster can discover
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each other and elect a master node.
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[discrete]
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[[unicast.hosts]]
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==== `discovery.seed_hosts`
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Out of the box, without any network configuration, Elasticsearch will bind to
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the available loopback addresses and will scan local ports 9300 to 9305 to try
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to connect to other nodes running on the same server. This provides an
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auto-clustering experience without having to do any configuration.
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When you want to form a cluster with nodes on other hosts, you should use the
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`discovery.seed_hosts` setting to provide a list of other nodes in the cluster
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that are master-eligible and likely to be live and contactable in order to seed
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the <<modules-discovery-hosts-providers,discovery process>>. This setting
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should be a list of the addresses of all the master-eligible nodes in the
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cluster. Each address can be either an IP address or a hostname which resolves
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to one or more IP addresses via DNS.
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If your master-eligible nodes do not have fixed names or addresses, use an
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<<built-in-hosts-providers,alternative hosts provider>> to find their addresses
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dynamically.
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[discrete]
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[[initial_master_nodes]]
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==== `cluster.initial_master_nodes`
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When you start a brand new Elasticsearch cluster for the very first time, there
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is a <<modules-discovery-bootstrap-cluster,cluster bootstrapping>> step, which
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determines the set of master-eligible nodes whose votes are counted in the very
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first election. In <<dev-vs-prod-mode,development mode>>, with no discovery
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settings configured, this step is automatically performed by the nodes
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themselves. As this auto-bootstrapping is <<modules-discovery-quorums,inherently
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unsafe>>, when you start a brand new cluster in <<dev-vs-prod-mode,production
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mode>>, you must explicitly list the master-eligible nodes whose votes should be
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counted in the very first election. This list is set using the
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`cluster.initial_master_nodes` setting. You should not use this setting when
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restarting a cluster or adding a new node to an existing cluster.
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[source,yaml]
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--------------------------------------------------
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discovery.seed_hosts:
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- 192.168.1.10:9300
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- 192.168.1.11 <1>
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- seeds.mydomain.com <2>
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- [0:0:0:0:0:ffff:c0a8:10c]:9301 <3>
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cluster.initial_master_nodes: <4>
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- master-node-a
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- master-node-b
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- master-node-c
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--------------------------------------------------
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<1> The port is optional and usually defaults to `9300`, but this default can
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be <<built-in-hosts-providers,overridden>> by certain settings.
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<2> If a hostname resolves to multiple IP addresses then the node will attempt to
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discover other nodes at all resolved addresses.
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<3> IPv6 addresses must be enclosed in square brackets.
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<4> The initial master nodes should be identified by their
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<<node.name,`node.name`>>, which defaults to their hostname. Make sure that
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the value in `cluster.initial_master_nodes` matches the `node.name`
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exactly. If you use a fully-qualified domain name such as
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`master-node-a.example.com` for your node names then you must use the
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fully-qualified name in this list; conversely if `node.name` is a bare
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hostname without any trailing qualifiers then you must also omit the
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trailing qualifiers in `cluster.initial_master_nodes`.
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For more information, see <<modules-discovery-bootstrap-cluster>> and
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<<modules-discovery-settings>>.
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