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Added examples to cross cluster search of using cluster settings

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Clinton Gormley 2017-04-04 13:34:16 +02:00
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docs/reference/modules/cross-cluster-search.asciidoc
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@ -1,24 +1,31 @@
[[modules-cross-cluster-search]] [[modules-cross-cluster-search]]
== Cross cluster search == Cross Cluster Search
experimental[] beta[]
The _cross cluster search_ feature allows any node to act as a federated client across The _cross cluster search_ feature allows any node to act as a federated client across
multiple clusters. In contrast to the _tribe_ feature, a _cross cluster search_ node won't multiple clusters. In contrast to the <<modules-tribe,tribe node>> feature, a cross cluster search node won't
join the remote cluster, instead it connects to a remote cluster in a light fashion in order to execute join the remote cluster, instead it connects to a remote cluster in a light fashion in order to execute
federated search requests. federated search requests.
The _cross cluster search_ feature works by configuring a remote cluster in the cluster state and connects only to a Cross cluster search works by configuring a remote cluster in the cluster state and connecting only to a
limited number of nodes in the remote cluster. Each remote cluster is referenced by a name and a list of seed nodes. limited number of nodes in the remote cluster. Each remote cluster is referenced by a name and a list of seed nodes.
Those seed nodes are used to discover other nodes eligible as so-called _gateway nodes_. Each node in a cluster that Those seed nodes are used to discover nodes in the remote cluster which are eligible as _gateway nodes_.
has remote clusters configured connects to one or more _gateway nodes_ and uses them to federate search requests to Each node in a cluster that has remote clusters configured connects to one or more _gateway nodes_ and uses
the remote cluster. them to federate search requests to the remote cluster.
Remote clusters can either be configured as part of the `elasticsearch.yml` file or be dynamically updated via [float]
the <<cluster-update-settings,cluster settings API>>. If a remote cluster is configured via `elasticsearch.yml` only === Configuring Cross Cluster Search
the nodes with the configuration set will be connecting to the remote cluster in which case federated search requests
will have to be sent specifically to those nodes. Remote clusters set via the Remote clusters can be specified globally using <<cluster-update-settings,cluster settings>>
<<cluster-update-settings,cluster settings API>> will be available on every node in the cluster. (which can be updated dynamically), or local to individual nodes using the
`elasticsearch.yml` file.
If a remote cluster is configured via `elasticsearch.yml` only the nodes with
that configuration will be able to connect to the remote cluster. In other
words, federated search requests will have to be sent specifically to those
nodes. Remote clusters set via the <<cluster-update-settings,cluster settings API>>
will be available on every node in the cluster.
The `elasticsearch.yml` config file for a _cross cluster search_ node just needs to list the The `elasticsearch.yml` config file for a _cross cluster search_ node just needs to list the
remote clusters that should be connected to, for instance: remote clusters that should be connected to, for instance:
@ -36,6 +43,55 @@ search:
<1> `cluster_one` and `cluster_two` are arbitrary cluster aliases representing the connection to each cluster. <1> `cluster_one` and `cluster_two` are arbitrary cluster aliases representing the connection to each cluster.
These names are subsequently used to distinguish between local and remote indices. These names are subsequently used to distinguish between local and remote indices.
The equivalent example using the <<cluster-update-settings,cluster settings API>>
to add remote clusters to all nodes in the cluster would look like the
following:
[source,js]
--------------------------------
PUT _cluster/settings
{
"persistent": {
"search": {
"remote": {
"cluster_one": {
"seeds": [
"127.0.0.1:9300"
]
},
"cluster_two": {
"seeds": [
"127.0.0.1:9301"
]
}
}
}
}
}
--------------------------------
// CONSOLE
A remote cluster can be deleted from the cluster settings by setting its seeds to `null`:
[source,js]
--------------------------------
PUT _cluster/settings
{
"persistent": {
"search": {
"remote": {
"cluster_one": {
"seeds": null <1>
}
}
}
}
}
--------------------------------
// CONSOLE
<1> `cluster_one` would be removed from the cluster settings, leaving `cluster_two` intact.
[float] [float]
=== Using cross cluster search === Using cross cluster search
@ -126,9 +182,11 @@ will be prefixed with their remote cluster name:
connected to if `search.remote.node.attr` is set to `gateway`. connected to if `search.remote.node.attr` is set to `gateway`.
`search.remote.connect`:: `search.remote.connect`::
By default, any node in the cluster can act as a cross-cluster client and connect to remote clusters.
The `search.remote.connect` setting can be set to `false` (defaults to `true`) to prevent certain nodes from By default, any node in the cluster can act as a cross-cluster client and
connecting to remote clusters. Cross-cluster search requests must be sent to a node that is allowed to act as a connect to remote clusters. The `search.remote.connect` setting can be set
cross-cluster client. to `false` (defaults to `true`) to prevent certain nodes from connecting to
remote clusters. Cross-cluster search requests must be sent to a node that
is allowed to act as a cross-cluster client.