This page contains the information you need to create an instance of the .NET Client for Elasticsearch that connects to your Elasticsearch cluster.

It’s possible to connect to your Elasticsearch cluster via a single node, or by specifying multiple nodes using a node pool. Using a node pool has a few advantages over a single node, such as load balancing and cluster failover support. The client provides convenient configuration options to connect to an Elastic Cloud deployment.

Client applications should create a single instance of ElasticsearchClient that is used throughout your application for its entire lifetime. Internally the client manages and maintains HTTP connections to nodes, reusing them to optimize performance. If you use a dependency injection container for your application, the client instance should be registered with a singleton lifetime.

Connecting to a cloud deploymentedit

Elastic Cloud is the easiest way to get started with Elasticsearch. When connecting to Elastic Cloud with the .NET Elasticsearch client you should always use the Cloud ID. You can find this value within the "Manage Deployment" page after you’ve created a cluster (look in the top-left if you’re in Kibana).

We recommend using a Cloud ID whenever possible because your client will be automatically configured for optimal use with Elastic Cloud, including HTTPS and HTTP compression.

Connecting to an Elasticsearch Service deployment is achieved by providing the unique Cloud ID for your deployment when configuring the ElasticsearchClient instance. You also require suitable credentials, either a username and password or an API key that your application uses to authenticate with your deployment.

As a security best practice, it is recommended to create a dedicated API key per application, with permissions limited to only those required for any API calls the application is authorized to make.

The following snippet demonstrates how to create a client instance that connects to an Elasticsearch deployment in the cloud.

using Elastic.Clients.Elasticsearch;
using Elastic.Transport;

var client = new ElasticsearchClient("<CLOUD_ID>", new ApiKey("<API_KEY>")); 

Replace the placeholder string values above with your cloud ID and the API key configured for your application to access your deployment.

Connecting to a single nodeedit

Single node configuration is best suited to connections to a multi-node cluster running behind a load balancer or reverse proxy, which is exposed via a single URL. It may also be convenient to use a single node during local application development. If the URL represents a single Elasticsearch node, be aware that this offers no resiliency should the server be unreachable or unresponsive.

By default, security features such as authentication and TLS are enabled on Elasticsearch clusters. When you start Elasticsearch for the first time, TLS is configured automatically for the HTTP layer. A CA certificate is generated and stored on disk which is used to sign the certificates for the HTTP layer of the Elasticsearch cluster.

In order for the client to establish a connection with the cluster over HTTPS, the CA certificate must be trusted by the client application. The simplest choice is to use the hex-encoded SHA-256 fingerprint of the CA certificate. The CA fingerprint is output to the terminal when you start Elasticsearch for the first time. You’ll see a distinct block like the one below in the output from Elasticsearch (you may have to scroll up if it’s been a while):

-> Elasticsearch security features have been automatically configured!
-> Authentication is enabled and cluster connections are encrypted.

->  Password for the elastic user (reset with `bin/elasticsearch-reset-password -u elastic`):

->  HTTP CA certificate SHA-256 fingerprint:

Note down the elastic user password and HTTP CA fingerprint for the next sections.

The CA fingerprint can also be retrieved at any time from a running cluster using the following command:

openssl x509 -fingerprint -sha256 -in config/certs/http_ca.crt

The command returns the security certificate, including the fingerprint. The issuer should be Elasticsearch security auto-configuration HTTP CA.

issuer= /CN=Elasticsearch security auto-configuration HTTP CA
SHA256 Fingerprint=<FINGERPRINT>

Visit the Start the Elastic Stack with security enabled automatically documentation for more information.

The following snippet shows you how to create a client instance that connects to your Elasticsearch cluster via a single node, using the CA fingerprint:

using Elastic.Clients.Elasticsearch;
using Elastic.Transport;

var settings = new ElasticsearchClientSettings(new Uri("https://localhost:9200"))
    .Authentication(new BasicAuthentication("<USERNAME>", "<PASSWORD>"));

var client = new ElasticsearchClient(settings);

The preceding snippet demonstrates configuring the client to authenticate by providing a username and password with basic authentication. If preferred, you may also use ApiKey authentication as shown in the cloud connection example.

Connecting to multiple nodes using a node pooledit

To provide resiliency, you should configure multiple nodes for your cluster to which the client attempts to communicate. By default, the client cycles through nodes for each request in a round robin fashion. The client also tracks unhealthy nodes and avoids sending requests to them until they become healthy.

This configuration is best suited to connect to a known small sized cluster, where you do not require sniffing to detect the cluster topology.

The following snippet shows you how to connect to multiple nodes by using a static node pool:

using Elastic.Clients.Elasticsearch;
using Elastic.Transport;

var nodes = new Uri[]
	new Uri("https://myserver1:9200"),
	new Uri("https://myserver2:9200"),
	new Uri("https://myserver3:9200")

var pool = new StaticNodePool(nodes);

var settings = new ElasticsearchClientSettings(pool)
    .Authentication(new ApiKey("<API_KEY>"));

var client = new ElasticsearchClient(settings);