110 lines
4.4 KiB
Plaintext
110 lines
4.4 KiB
Plaintext
[[client]]
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== Client
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You can use the *Java client* in multiple ways:
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* Perform standard <<java-docs-index,index>>, <<java-docs-get,get>>,
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<<java-docs-delete,delete>> and <<java-search,search>> operations on an
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existing cluster
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* Perform administrative tasks on a running cluster
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Obtaining an elasticsearch `Client` is simple. The most common way to
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get a client is by creating a <<transport-client,`TransportClient`>>
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that connects to a cluster.
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[IMPORTANT]
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==============================
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The client must have the same major version (e.g. `2.x`, or `5.x`) as the
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nodes in the cluster. Clients may connect to clusters which have a different
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minor version (e.g. `2.3.x`) but it is possible that new funcionality may not
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be supported. Ideally, the client should have the same version as the
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cluster.
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==============================
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[[transport-client]]
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=== Transport Client
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The `TransportClient` connects remotely to an Elasticsearch cluster
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using the transport module. It does not join the cluster, but simply
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gets one or more initial transport addresses and communicates with them
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in round robin fashion on each action (though most actions will probably
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be "two hop" operations).
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[source,java]
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--------------------------------------------------
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// on startup
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Client client = TransportClient.builder().build()
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.addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName("host1"), 9300))
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.addTransportAddress(new InetSocketTransportAddress(InetAddress.getByName("host2"), 9300));
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// on shutdown
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client.close();
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--------------------------------------------------
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Note that you have to set the cluster name if you use one different than
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"elasticsearch":
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[source,java]
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--------------------------------------------------
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Settings settings = Settings.builder()
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.put("cluster.name", "myClusterName").build();
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Client client = TransportClient.builder().settings(settings).build();
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//Add transport addresses and do something with the client...
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--------------------------------------------------
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The Transport client comes with a cluster sniffing feature which
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allows it to dynamically add new hosts and remove old ones.
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When sniffing is enabled the the transport client will connect to the nodes in its
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internal node list, which is built via calls to addTransportAddress.
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After this, the client will call the internal cluster state API on those nodes
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to discover available data nodes. The internal node list of the client will
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be replaced with those data nodes only. This list is refreshed every five seconds by default.
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Note that the IP addresses the sniffer connects to are the ones declared as the 'publish'
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address in those node's elasticsearch config.
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Keep in mind that list might possibly not include the original node it connected to
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if that node is not a data node. If, for instance, you initially connect to a
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master node, after sniffing no further requests will go to that master node,
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but rather to any data nodes instead. The reason the transport excludes non-data
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nodes is to avoid sending search traffic to master only nodes.
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In order to enable sniffing, set `client.transport.sniff` to `true`:
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[source,java]
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--------------------------------------------------
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Settings settings = Settings.settingsBuilder()
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.put("client.transport.sniff", true).build();
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TransportClient client = TransportClient.builder().settings(settings).build();
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--------------------------------------------------
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Other transport client level settings include:
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[cols="<,<",options="header",]
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|=======================================================================
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|Parameter |Description
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|`client.transport.ignore_cluster_name` |Set to `true` to ignore cluster
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name validation of connected nodes. (since 0.19.4)
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|`client.transport.ping_timeout` |The time to wait for a ping response
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from a node. Defaults to `5s`.
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|`client.transport.nodes_sampler_interval` |How often to sample / ping
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the nodes listed and connected. Defaults to `5s`.
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|=======================================================================
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[[client-connected-to-client-node]]
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=== Connecting a Client to a Coordinating Only Node
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You can start locally a {ref}/modules-node.html#coordinating-only-node[Coordinating Only Node]
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and then simply create a <<transport-client,`TransportClient`>> in your
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application which connects to this Coordinating Only Node.
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This way, the coordinating only node will be able to load whatever plugin you
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need (think about discovery plugins for example).
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