Separate remote clusters docs from CCS #34612
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| [[modules-remote-clusters]] | ||
| == Remote clusters | ||
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| ifndef::include-xpack[] | ||
| The _remote clusters_ module allows establishing uni-directional connections to | ||
| a remote cluster. This functionality is used in | ||
| <<modules-cross-cluster-search,cross-cluster search>>. | ||
| endif::[] | ||
| ifdef::include-xpack[] | ||
| The _remote clusters_ module allows establishing uni-directional connections to | ||
| a remote cluster. This functionality is used in cross-cluster replication, | ||
| <<modules-cross-cluster-search,cross-cluster search>>. | ||
| endif::[] | ||
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| Remote cluster connections work by configuring a remote cluster 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. When a remote cluster is | ||
| registered, its cluster state is retrieved from one of the seed nodes so that by | ||
| default up to three _gateway nodes_ are selected to be connected to as part of | ||
| remote cluster requests. Remote cluster connections consist of uni-directional | ||
| connections from the coordinating node to the previously selected remote nodes | ||
| only. It is possible to tag which nodes should be selected through node | ||
| attributes (see <<remote-cluster-settings>>). | ||
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| Each node in a cluster that has remote clusters configured connects to one or | ||
| more _gateway nodes_ and uses them to federate requests to the remote cluster. | ||
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| [float] | ||
| [[configuring-remote-clusters]] | ||
| === Configuring Remote Clusters | ||
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| Remote clusters can be specified globally using | ||
| <<cluster-update-settings,cluster settings>> (which can be updated dynamically), | ||
| or local to individual nodes using the `elasticsearch.yml` file. | ||
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| 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, functionality that relies on remote cluster requests will have to be | ||
|
Member
There was a problem hiding this comment. This seems like a very particular feature. Almost like we'd be better off giving the advice to set the remote cluster up in every |
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| driven specifically from those nodes. Remote clusters set via the | ||
| <<cluster-update-settings,cluster settings API>> will be available on every node | ||
|
Member
There was a problem hiding this comment. This sentence feels out of order with the one after it. |
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| in the cluster. | ||
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| The `elasticsearch.yml` config file for a node that connects to remote clusters | ||
| needs to list the remote clusters that should be connected to, for instance: | ||
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| [source,yaml] | ||
| -------------------------------- | ||
| cluster: | ||
| remote: | ||
| cluster_one: <1> | ||
| seeds: 127.0.0.1:9300 | ||
| cluster_two: <1> | ||
| seeds: 127.0.0.1:9301 | ||
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| -------------------------------- | ||
| <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. | ||
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| 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: | ||
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| [source,js] | ||
| -------------------------------- | ||
| PUT _cluster/settings | ||
| { | ||
| "persistent": { | ||
| "cluster": { | ||
| "remote": { | ||
| "cluster_one": { | ||
| "seeds": [ | ||
| "127.0.0.1:9300" | ||
| ] | ||
| }, | ||
| "cluster_two": { | ||
| "seeds": [ | ||
| "127.0.0.1:9301" | ||
| ] | ||
| }, | ||
| "cluster_three": { | ||
| "seeds": [ | ||
| "127.0.0.1:9302" | ||
| ] | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| -------------------------------- | ||
| // CONSOLE | ||
| // TEST[setup:host] | ||
| // TEST[s/127.0.0.1:9300/\${transport_host}/] | ||
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| A remote cluster can be deleted from the cluster settings by setting its seeds | ||
| to `null`: | ||
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| [source,js] | ||
| -------------------------------- | ||
| PUT _cluster/settings | ||
| { | ||
| "persistent": { | ||
| "cluster": { | ||
| "remote": { | ||
| "cluster_three": { | ||
| "seeds": null <1> | ||
| } | ||
| } | ||
| } | ||
| } | ||
| } | ||
| -------------------------------- | ||
| // CONSOLE | ||
| // TEST[continued] | ||
| <1> `cluster_three` would be removed from the cluster settings, leaving | ||
| `cluster_one` and `cluster_two` intact. | ||
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| [float] | ||
| [[remote-cluster-settings]] | ||
| === Remote cluster settings | ||
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| `cluster.remote.connections_per_cluster`:: | ||
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| The number of gateway nodes to connect to per remote cluster. The default is | ||
| `3`. | ||
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| `cluster.remote.initial_connect_timeout`:: | ||
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| The time to wait for remote connections to be established when the node | ||
| starts. The default is `30s`. | ||
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| `cluster.remote.node.attr`:: | ||
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| A node attribute to filter out nodes that are eligible as a gateway node in | ||
| the remote cluster. For instance a node can have a node attribute | ||
| `node.attr.gateway: true` such that only nodes with this attribute will be | ||
| connected to if `cluster.remote.node.attr` is set to `gateway`. | ||
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| `cluster.remote.connect`:: | ||
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| By default, any node in the cluster can act as a cross-cluster client and | ||
| connect to remote clusters. The `cluster.remote.connect` setting can be set to | ||
| `false` (defaults to `true`) to prevent certain nodes from connecting to | ||
| remote clusters. Remote cluster requests must be sent to a node that is | ||
| allowed to act as a cross-cluster client. | ||
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| `cluster.remote.${cluster_alias}.skip_unavailable`:: | ||
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| Per cluster boolean setting that allows to skip specific clusters when no | ||
| nodes belonging to them are available and they are the targetof a remote | ||
| cluster request. Default is `false`, meaning that all clusters are mandatory | ||
| by default, but they can selectively be made optional by setting this setting | ||
| to `true`. | ||
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| [float] | ||
| [[retrieve-remote-clusters-info]] | ||
| === Retrieving remote clusters info | ||
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| The <<cluster-remote-info, Remote Cluster Info API>> allows to retrieve | ||
| information about the configured remote clusters, as well as the remote nodes | ||
| that the node is connected to. | ||
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should we rather say
proxythanfederate?