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Separate remote clusters docs from CCS (#34612) 

With remote clusters taking on a larger role, we have make the
infrastructure more generic than being tied to cross-cluster search
(CCS). We want to refer to the remote clusters configuration in the
cross-cluster replication (CCR) docs. Yet, these docs are still tied to
CCS. This commit extracts the remote clusters docs from CCS (with some
wording changes to make them more general) so that we can refer to them
in the CCR docs.
This commit is contained in:
Jason Tedor 2018-10-20 08:33:59 -04:00 committed by GitHub
parent 9fb2f7cc20
commit b2dc58450e
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3 changed files with 167 additions and 167 deletions
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4
docs/reference/modules.asciidoc
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@ -73,6 +73,8 @@ The modules in this section are:
Configure the transport networking layer, used internally by Elasticsearch
to communicate between nodes.
<<modules-remote-cluster, Remote cluster>>::
Remote clusters are used in features that work by connecting across clusters on the transport layer.
<<modules-cross-cluster-search, Cross cluster Search>>::
@ -106,4 +108,6 @@ include::modules/threadpool.asciidoc[]
include::modules/transport.asciidoc[]
include::modules/remote-clusters.asciidoc[]
include::modules/cross-cluster-search.asciidoc[]

169
docs/reference/modules/cross-cluster-search.asciidoc
View File

@ -6,52 +6,10 @@ multiple clusters. A cross cluster search node won't join the remote cluster, in
it connects to a remote cluster in a light fashion in order to execute
federated search requests.
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.
When a remote cluster is registered, its cluster state is retrieved from one of the seed nodes so that up to 3
_gateway nodes_ are selected to be connected to as part of upcoming cross cluster search requests.
Cross cluster search requests 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 <<cross-cluster-search-settings>>).
Each node in a cluster that has remote clusters configured connects to one or more _gateway nodes_ and uses
them to federate search requests to the remote cluster.
[float]
=== Configuring Cross Cluster Search
=== Using cross cluster search
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.
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.
[WARNING]
This feature was added as Beta in Elasticsearch `v5.3` with further improvements made in 5.4 and 5.5. It requires gateway eligible nodes to be on `v5.5` onwards.
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:
[source,yaml]
--------------------------------
cluster:
remote:
cluster_one: <1>
seeds: 127.0.0.1:9300
cluster_two: <1>
seeds: 127.0.0.1:9301
--------------------------------
<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.
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:
Cross-cluster search requires <<modules-remote-clusters,configuring remote clusters>>.
[source,js]
--------------------------------
@ -84,85 +42,6 @@ PUT _cluster/settings
// TEST[setup:host]
// TEST[s/127.0.0.1:9300/\${transport_host}/]
//////////////////////////
We want to be sure that settings have been updated,
because we'll use them later.
[source,js]
--------------------------------------------------
{
"acknowledged" : true,
"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"
]
}
}
}
},
"transient" : {}
}
--------------------------------------------------
// TESTRESPONSE[s/127.0.0.1:9300/\${transport_host}/]
//////////////////////////
A remote cluster can be deleted from the cluster settings by setting its seeds to `null`:
[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.
//////////////////////////
We want to be sure that settings have been updated,
because we'll use them later.
[source,js]
--------------------------------------------------
{
"acknowledged" : true,
"persistent" : {},
"transient" : {}
}
--------------------------------------------------
// TESTRESPONSE
//////////////////////////
[float]
=== Using cross cluster search
To search the `twitter` index on remote cluster `cluster_one` the index name
must be prefixed with the cluster alias separated by a `:` character:
@ -385,47 +264,3 @@ GET /cluster_one:twitter,cluster_two:twitter,twitter/_search <1>
// TESTRESPONSE[s/"_score": 1/"_score": "$body.hits.hits.0._score"/]
// TESTRESPONSE[s/"_score": 2/"_score": "$body.hits.hits.1._score"/]
<1> The `clusters` section indicates that one cluster was unavailable and got skipped
[float]
[[cross-cluster-search-settings]]
=== Cross cluster search settings
`cluster.remote.connections_per_cluster`::
The number of nodes to connect to per remote cluster. The default is `3`.
`cluster.remote.initial_connect_timeout`::
The time to wait for remote connections to be established when the node starts. The default is `30s`.
`cluster.remote.node.attr`::
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`.
`cluster.remote.connect`::
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. Cross-cluster search requests must be sent to a node that
is allowed to act as a cross-cluster client.
`cluster.remote.${cluster_alias}.skip_unavailable`::
Per cluster boolean setting that allows to skip specific clusters when no
nodes belonging to them are available and they are searched as part of a
cross cluster search 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`.
[float]
[[retrieve-remote-clusters-info]]
=== Retrieving remote clusters info
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 Cross Cluster Search node is connected to.

161
docs/reference/modules/remote-clusters.asciidoc Normal file
View File

@ -0,0 +1,161 @@
[[modules-remote-clusters]]
== Remote clusters
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::[]
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>>).
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.
[float]
[[configuring-remote-clusters]]
=== Configuring Remote Clusters
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.
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
driven specifically from 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 node that connects to remote clusters
needs to list the remote clusters that should be connected to, for instance:
[source,yaml]
--------------------------------
cluster:
remote:
cluster_one: <1>
seeds: 127.0.0.1:9300
cluster_two: <1>
seeds: 127.0.0.1:9301
--------------------------------
<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.
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": {
"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}/]
A remote cluster can be deleted from the cluster settings by setting its seeds
to `null`:
[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.
[float]
[[remote-cluster-settings]]
=== Remote cluster settings
`cluster.remote.connections_per_cluster`::
The number of gateway nodes to connect to per remote cluster. The default is
`3`.
`cluster.remote.initial_connect_timeout`::
The time to wait for remote connections to be established when the node
starts. The default is `30s`.
`cluster.remote.node.attr`::
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`.
`cluster.remote.connect`::
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.
`cluster.remote.${cluster_alias}.skip_unavailable`::
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`.
[float]
[[retrieve-remote-clusters-info]]
=== Retrieving remote clusters info
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.