add basic docs
This commit is contained in:
Simon Willnauer
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dca54734ac
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@ -86,7 +86,7 @@ public final class RemoteClusterService extends AbstractComponent implements Clo
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/**
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* The name of a node attribute to filter out nodes that should not be connected to in the remote cluster.
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* For instance a node can be configured with <tt>node.node_attr.gateway: true</tt> in order to be eligable as a gateway node between
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* For instance a node can be configured with <tt>node.node_attr.gateway: true</tt> in order to be eligible as a gateway node between
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* clusters. In that case <tt>search.remote.node_attribute: gateway</tt> can be used to filter out other nodes in the remote cluster
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*/
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public static final Setting<String> REMOTE_NODE_ATTRIBUTE = Setting.simpleString("search.remote.node_attribute",
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@ -157,7 +157,7 @@ public final class RemoteClusterService extends AbstractComponent implements Clo
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return remoteClusters.isEmpty() == false;
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}
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public String[] filterIndices(Map<String, List<String>> perClusterIndices, String... requestIndices) {
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public String[] filterIndices(Map<String, List<String>> perClusterIndices, String[] requestIndices) {
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List<String> localIndicesList = new ArrayList<>();
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for (String index : requestIndices) {
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int i = index.indexOf(REMOTE_CLUSTER_INDEX_SEPARATOR);
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@ -124,7 +124,7 @@ public class TransportSearchAction extends HandledTransportAction<SearchRequest,
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final Map<String, List<String>> remoteIndicesByCluster;
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if (remoteClusterService.isCrossClusterSearchEnabled()) {
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remoteIndicesByCluster = new HashMap<>();
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localIndices = remoteClusterService.filterIndices(remoteIndicesByCluster);
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localIndices = remoteClusterService.filterIndices(remoteIndicesByCluster, searchRequest.indices());
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} else {
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remoteIndicesByCluster = Collections.emptyMap();
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localIndices = searchRequest.indices();
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@ -257,7 +257,7 @@ public final class ClusterSettings extends AbstractScopedSettings {
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RemoteClusterService.REMOTE_CLUSTERS_SEEDS,
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RemoteClusterService.REMOTE_CONNECTIONS_PER_CLUSTER,
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RemoteClusterService.REMOTE_INITIAL_CONNECTION_TIMEOUT_SETTING,
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RemoteClusterServic.REMOTE_NODE_ATTRIBUTE
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RemoteClusterService.REMOTE_NODE_ATTRIBUTE,
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TransportService.TRACE_LOG_EXCLUDE_SETTING,
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TransportService.TRACE_LOG_INCLUDE_SETTING,
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TransportCloseIndexAction.CLUSTER_INDICES_CLOSE_ENABLE_SETTING,
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@ -145,6 +145,7 @@ buildRestTests.expectedUnconvertedCandidates = [
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'reference/modules/scripting/security.asciidoc',
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'reference/modules/scripting/using.asciidoc',
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'reference/modules/transport.asciidoc',
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'reference/modules/cross-cluster-search.asciidoc', // this is hart to test since we need 2 clusters -- maybe we can trick it into referencing itself...
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'reference/query-dsl/exists-query.asciidoc',
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'reference/query-dsl/function-score-query.asciidoc',
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'reference/query-dsl/geo-shape-query.asciidoc',
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@ -77,6 +77,11 @@ The modules in this section are:
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A tribe node joins one or more clusters and acts as a federated
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client across them.
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<<modules-cross-cluster-search, Cross cluster Search>>::
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Cross cluster search allows to execute search requests across more than one cluster without joining them and acts
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as a federated client across them.
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--
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@ -0,0 +1,112 @@
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[[modules-cross-cluster-search]]
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== Cross cluster search
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The _cross cluster search_ feature allows any node to act as a federated client across
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multiple clusters. In contrast to the _tribe_ feature, a _cross cluster search_ node won't
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join the remote cluster, instead it connects to a remote cluster in a light fashion in order to executed
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federated search requests.
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The _cross cluster search_ feature works by configuring a remote cluster in the cluster state and connects only to a
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limited number of nodes in the remote cluster. Each remote cluster is referenced by a name and a list of seed nodes.
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Those seed nodes are used to discover other nodes eligible as so-called _gateway nodes_. Each node in a cluster that
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has remote cluster configured connects to one or more _gateway nodes_ and uses them to federate search requests to
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the remote cluster.
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Remote clusters can either be configured as part of the `elasticsearch.yml` file or be dynamically updated via
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the <<cluster settings API, cluster-update-settings>>. If a remote cluster is configured via `elasticsearch.yml` only
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the nodes with the configuration set will be connecting to the remote cluster. Remote clusters set via the
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<<cluster settings API, cluster-update-settings>> will be available on every node in the cluster.
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The `elasticsearch.yml` config file for a _cross cluster search_ node just needs to list the
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remote clusters that should be connected to, for instance:
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[source,yaml]
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--------------------------------
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search:
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remote:
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seeds:
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cluster_one: 127.0.0.1:9300 <1>
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cluster_two: 127.0.0.1:9301 <1>
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--------------------------------
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<1> `cluster_one` and `cluster_two` are arbitrary names representing the connection to each cluster. These names are subsequently used to distinguish between local and remote indices.
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[float]
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=== Using cross cluster search
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To search the `twitter` index on remote cluster `cluster_1` the index name must be prefixed with the cluster name
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separated by a `|` character:
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[source,js]
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--------------------------------------------------
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POST /cluster_1|twitter/tweet/_search
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{
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"match_all": {}
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}
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--------------------------------------------------
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In contrast to the `tribe` feature cross cluster search can also search indices with the same name on different clusters:
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[source,js]
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--------------------------------------------------
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POST /cluster_1|twitter,twitter/tweet/_search
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{
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"match_all": {}
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}
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--------------------------------------------------
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Search results are disambiguated the same way as the indices are disambiguated in the request. Even if index names are
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identical these indices will be treated as different indices when results are merged. All results retrieved from a remote index
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will be prefixed with it's remote clusters name:
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[source,js]
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--------------------------------------------------
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{
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"took" : 89,
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"timed_out" : false,
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"_shards" : {
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"total" : 10,
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"successful" : 10,
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"failed" : 0
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},
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"hits" : {
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"total" : 2,
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"max_score" : 1.0,
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"hits" : [
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{
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"_index" : "cluster_1|twitter",
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"_type" : "tweet",
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"_id" : "1",
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"_score" : 1.0,
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"_source" : {
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"user" : "kimchy",
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"postDate" : "2009-11-15T14:12:12",
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"message" : "trying out Elasticsearch"
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}
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},
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{
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"_index" : "cluster_1|twitter",
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"_type" : "tweet",
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"_id" : "1",
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"_score" : 1.0,
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"_source" : {
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"user" : "kimchy",
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"postDate" : "2009-11-15T14:12:12",
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"message" : "trying out Elasticsearch"
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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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[float]
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=== Cross cluster search settings
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* `search.remote.connections_per_cluster` - the number of nodes to connect to per remote cluster. The default is `3`
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* `search.remote.initial_connect_timeout` - the time to wait for remote connections to be established when the node starts. The default is `30s`.
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* `search.remote.node_attribute` - a node attribute to filter out nodes that are eligible as a gateway node in the remote cluster.
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For instance a node can have a node attribute `node.attr.gateway: true` such that only nodes with this attribute
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will be connected to if `search.remote.node_attribute` is set to `gateway`
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