Further clarify cluster.initial_master_nodes (#41179)
The following phrase causes confusion: > Alternatively the IP addresses or hostnames (if node name defaults to the > host name) can be used. This change clarifies the conditions under which you can use a hostname, and adds an anchor to the note introduced in (#41137) so we can link directly to it in conversations with users.
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David Turner
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c8bc4ab003
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5ef247dc91
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@ -10,15 +10,20 @@ data folder and freshly-started nodes that are joining an existing cluster
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obtain this information from the cluster's elected master.
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The initial set of master-eligible nodes is defined in the
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<<initial_master_nodes,`cluster.initial_master_nodes` setting>>. When you
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start a master-eligible node, you can provide this setting on the command line
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or in the `elasticsearch.yml` file. After the cluster has formed, this setting
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is no longer required and is ignored. It need not be set
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on master-ineligible nodes, nor on master-eligible nodes that are started to
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join an existing cluster. Note that master-eligible nodes should use storage
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that persists across restarts. If they do not, and
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`cluster.initial_master_nodes` is set, and a full cluster restart occurs, then
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another brand-new cluster will form and this may result in data loss.
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<<initial_master_nodes,`cluster.initial_master_nodes` setting>>. This is a list
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of the <<node.name,node names>> or IP addresses of the master-eligible nodes in
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the new cluster. If you do not configure `node.name` then it is set to the
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node's hostname, so in this case you can use hostnames in
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`cluster.initial_master_nodes` too.
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When you start a master-eligible node, you can provide this setting on the
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command line or in the `elasticsearch.yml` file. After the cluster has formed,
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this setting is no longer required and is ignored. It need not be set on
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master-ineligible nodes, nor on master-eligible nodes that are started to join
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an existing cluster. Note that master-eligible nodes should use storage that
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persists across restarts. If they do not, and `cluster.initial_master_nodes` is
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set, and a full cluster restart occurs, then another brand-new cluster will
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form and this may result in data loss.
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It is technically sufficient to set `cluster.initial_master_nodes` on a single
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master-eligible node in the cluster, and only to mention that single node in the
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@ -42,10 +47,9 @@ cluster.initial_master_nodes:
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- master-c
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--------------------------------------------------
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Alternatively the IP addresses or hostnames (<<node.name,if node name defaults
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to the host name>>) can be used. If there is more than one Elasticsearch node
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with the same IP address or hostname then the transport ports must also be given
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to specify exactly which node is meant:
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You can use a mix of IP addresses and node names too. If there is more than one
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Elasticsearch node with the same IP address then the transport port must also
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be given to specify exactly which node is meant:
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[source,yaml]
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--------------------------------------------------
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@ -56,14 +60,23 @@ cluster.initial_master_nodes:
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- master-node-hostname
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--------------------------------------------------
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Like all node settings, it is also possible to specify the initial set of master
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nodes on the command-line that is used to start Elasticsearch:
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[source,bash]
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--------------------------------------------------
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$ bin/elasticsearch -Ecluster.initial_master_nodes=master-a,master-b,master-c
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--------------------------------------------------
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[NOTE]
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==================================================
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The node names used in this list must exactly match the `node.name` properties
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of the nodes. By default the node name is set to the machine's hostname which
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may or may not be fully-qualified depending on your system configuration. If
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each node name is a fully-qualified domain name such as `master-a.example.com`
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then you must use fully-qualified domain names in the
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[[modules-discovery-bootstrap-cluster-fqdns]] The node names used in the
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`cluster.initial_master_nodes` list must exactly match the `node.name`
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properties of the nodes. By default the node name is set to the machine's
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hostname which may or may not be fully-qualified depending on your system
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configuration. If each node name is a fully-qualified domain name such as
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`master-a.example.com` then you must use fully-qualified domain names in the
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`cluster.initial_master_nodes` list too; conversely if your node names are bare
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hostnames (without the `.example.com` suffix) then you must use bare hostnames
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in the `cluster.initial_master_nodes` list. If you use a mix of fully-qualifed
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@ -81,18 +94,11 @@ bootstrap a cluster: have discovered [{master-b.example.com}{...
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This message shows the node names `master-a.example.com` and
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`master-b.example.com` as well as the `cluster.initial_master_nodes` entries
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`master-a` and `master-b`, and it is apparent that they do not match exactly.
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`master-a` and `master-b`, and it is clear from this message that they do not
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match exactly.
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==================================================
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Like all node settings, it is also possible to specify the initial set of master
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nodes on the command-line that is used to start Elasticsearch:
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[source,bash]
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--------------------------------------------------
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$ bin/elasticsearch -Ecluster.initial_master_nodes=master-a,master-b,master-c
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--------------------------------------------------
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[float]
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==== Choosing a cluster name
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@ -58,15 +58,17 @@ cluster.initial_master_nodes:
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`transport.port` if not specified.
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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> Initial master nodes can be identified by their <<node.name,`node.name`>>.
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Make sure that the value here matches the `node.name` exactly. If you use a
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fully-qualified domain name such as `master-node-a.example.com` for your
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<3> Initial master nodes can be identified by their <<node.name,`node.name`>>,
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which defaults to the hostname. Make sure that the value in
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`cluster.initial_master_nodes` matches the `node.name` exactly. If you use
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a fully-qualified domain name such as `master-node-a.example.com` for your
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node names then you must use the fully-qualified name in this list;
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conversely if `node.name` is a bare hostname without any trailing
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qualifiers then you must also omit the trailing qualifiers in
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`cluster.initial_master_nodes`.
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<4> Initial master nodes can also be identified by their IP address.
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<5> If multiple master nodes share an IP address then the port must be used to
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disambiguate them.
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<5> If multiple master nodes share an IP address then the transport port must
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be used to distinguish between them.
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For more information, see <<modules-discovery-settings>>.
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For more information, see <<modules-discovery-bootstrap-cluster>> and
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<<modules-discovery-settings>>.
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