171 lines
5.8 KiB
Plaintext
171 lines
5.8 KiB
Plaintext
[[modules-remote-clusters]]
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== Remote clusters
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ifndef::include-xpack[]
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The _remote clusters_ module allows establishing uni-directional connections to
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a remote cluster. This functionality is used in
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<<modules-cross-cluster-search,cross-cluster search>>.
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endif::[]
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ifdef::include-xpack[]
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The _remote clusters_ module allows establishing uni-directional connections to
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a remote cluster. This functionality is used in cross-cluster replication, and
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<<modules-cross-cluster-search,cross-cluster search>>.
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endif::[]
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Remote cluster connections work by configuring a remote cluster and connecting
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only to a limited number of nodes in the remote cluster. Each remote cluster is
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referenced by a name and a list of seed nodes. When a remote cluster is
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registered, its cluster state is retrieved from one of the seed nodes so that by
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default up to three _gateway nodes_ are selected to be connected to as part of
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remote cluster requests. Remote cluster connections consist of uni-directional
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connections from the coordinating node to the previously selected remote nodes
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only. It is possible to tag which nodes should be selected through node
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attributes (see <<remote-cluster-settings>>).
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Each node in a cluster that has remote clusters configured connects to one or
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more _gateway nodes_ and uses them to federate requests to the remote cluster.
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[float]
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[[configuring-remote-clusters]]
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=== Configuring Remote Clusters
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Remote clusters can be specified globally using
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<<cluster-update-settings,cluster settings>> (which can be updated dynamically),
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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
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that configuration will be able to connect to the remote cluster. In other
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words, functionality that relies on remote cluster requests will have to be
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driven specifically from those nodes. Remote clusters set via the
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<<cluster-update-settings,cluster settings API>> will be available on every node
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in the cluster.
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The `elasticsearch.yml` config file for a node that connects to remote clusters
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needs to list the remote clusters that should be connected to, for instance:
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[source,yaml]
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--------------------------------
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cluster:
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remote:
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cluster_one: <1>
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seeds: 127.0.0.1:9300
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cluster_two: <1>
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seeds: 127.0.0.1:9301
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--------------------------------
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<1> `cluster_one` and `cluster_two` are arbitrary _cluster aliases_ representing
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the connection to each cluster. These names are subsequently used to distinguish
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between local and remote indices.
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The equivalent example using the <<cluster-update-settings,cluster settings
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API>> to add remote clusters to all nodes in the cluster would look like the
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following:
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[source,js]
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--------------------------------
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PUT _cluster/settings
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{
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"persistent": {
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"cluster": {
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"remote": {
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"cluster_one": {
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"seeds": [
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"127.0.0.1:9300"
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]
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},
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"cluster_two": {
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"seeds": [
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"127.0.0.1:9301"
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]
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},
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"cluster_three": {
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"seeds": [
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"127.0.0.1:9302"
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]
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}
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}
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}
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}
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}
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--------------------------------
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// CONSOLE
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// TEST[setup:host]
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// 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
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to `null`:
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[source,js]
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--------------------------------
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PUT _cluster/settings
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{
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"persistent": {
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"cluster": {
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"remote": {
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"cluster_three": {
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"seeds": null <1>
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}
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}
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}
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}
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}
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--------------------------------
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// CONSOLE
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// TEST[continued]
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<1> `cluster_three` would be removed from the cluster settings, leaving
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`cluster_one` and `cluster_two` intact.
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[float]
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[[remote-cluster-settings]]
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=== 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
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`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
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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
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the remote cluster. For instance a node can have a node attribute
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`node.attr.gateway: true` such that only nodes with this attribute will be
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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
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connect to remote clusters. The `cluster.remote.connect` setting can be set to
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`false` (defaults to `true`) to prevent certain nodes from connecting to
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remote clusters. Remote cluster requests must be sent to a node that is
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allowed to act as a cross-cluster client.
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`cluster.remote.${cluster_alias}.skip_unavailable`::
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Per cluster boolean setting that allows to skip specific clusters when no
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nodes belonging to them are available and they are the targetof a remote
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cluster request. Default is `false`, meaning that all clusters are mandatory
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by default, but they can selectively be made optional by setting this setting
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to `true`.
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`cluster.remote.${cluster_alias}.transport.ping_schedule`::
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Sets the time interval between regular application-level ping messages that
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are sent to ensure that transport connections to nodes belonging to remote
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clusters are kept alive. If set to `-1`, application-level ping messages to
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this remote cluster are not sent. If unset, application-level ping messages
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are sent according to the global `transport.ping_schedule` setting, which
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defaults to ``-1` meaning that pings are not sent.
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[float]
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[[retrieve-remote-clusters-info]]
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=== Retrieving remote clusters info
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The <<cluster-remote-info, Remote Cluster Info API>> allows to retrieve
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information about the configured remote clusters, as well as the remote nodes
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that the node is connected to.
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