Node Client
editNode Client
editInstantiating a node based client is the simplest way to get a Client
that can execute operations against elasticsearch.
import static org.elasticsearch.node.NodeBuilder.*; // on startup Node node = nodeBuilder().node(); Client client = node.client(); // on shutdown node.close();
When you start a Node
, it joins an elasticsearch cluster. You can have
different clusters by simply setting the cluster.name
setting, or
explicitly using the clusterName
method on the builder.
You can define cluster.name
in the /src/main/resources/elasticsearch.yml
file in your project. As long as elasticsearch.yml
is present in the
classpath, it will be used when you start your node.
cluster.name: yourclustername
Or in Java:
Node node = nodeBuilder().clusterName("yourclustername").node(); Client client = node.client();
The benefit of using the Client
is the fact that operations are
automatically routed to the node(s) the operations need to be executed
on, without performing a "double hop". For example, the index operation
will automatically be executed on the shard that it will end up existing
at.
When you start a Node
, the most important decision is whether it
should hold data or not. In other words, should indices and shards be
allocated to it. Many times we would like to have the clients just be
clients, without shards being allocated to them. This is simple to
configure by setting either node.data
setting to false
or
node.client
to true
(the NodeBuilder
respective helper methods on
it):
import static org.elasticsearch.node.NodeBuilder.*; // on startup // Embedded node clients behave just like standalone nodes, // which means that they will leave the HTTP port open! Node node = nodeBuilder() .settings(ImmutableSettings.settingsBuilder().put("http.enabled", false)) .client(true) .node(); Client client = node.client(); // on shutdown node.close();
Another common usage is to start the Node
and use the Client
in
unit/integration tests. In such a case, we would like to start a "local"
Node
(with a "local" discovery and transport). Again, this is just a
matter of a simple setting when starting the Node
. Note, "local" here
means local on the JVM (well, actually class loader) level, meaning that
two local servers started within the same JVM will discover themselves
and form a cluster.
import static org.elasticsearch.node.NodeBuilder.*; // on startup Node node = nodeBuilder().local(true).node(); Client client = node.client(); // on shutdown node.close();
Node Client Downsides
editEmbedding a node client into your application is the easiest way to connect to an Elasticsearch cluster, but it carries some downsides.
- Frequently starting and stopping one or more node clients creates unnecessary noise across the cluster.
-
Embedded node client will respond to outside requests, just like any other client.
- You almost always want to disable HTTP for an embedded node client.