Connecting

This page contains the information you need to connect and use the Client with Elasticsearch.

On this page

If you are using Elastic Cloud, the client offers an easy way to connect to it. You must pass the Cloud ID that you can find in the cloud console and the corresponding API key.

cfg := elasticsearch.Config{
        CloudID: "CLOUD_ID",
        APIKey: "API_KEY"
}
es, err := elasticsearch.NewClient(cfg)

Starting from version 8.0, Elasticsearch offers security by default with authentication and TLS enabled.

To connect to the Elasticsearch cluster you need to configure the client to use the generated CA certificate. If you’re just getting started with Elasticsearch we recommend reading the documentation on configuring and starting Elasticsearch to ensure your cluster is running as expected.

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`):
  lhQpLELkjkrawaBoaz0Q
->  HTTP CA certificate SHA-256 fingerprint:
  a52dd93511e8c6045e21f16654b77c9ee0f34aea26d9f40320b531c474676228
...
----------------------------------------------------------------

Note down the elastic user password and HTTP CA fingerprint for the next sections. In the examples below they will be stored in the variables ELASTIC_PASSWORD and CERT_FINGERPRINT respectively.

Depending on the circumstances there are two options for verifying the HTTPS connection, either verifying with the CA certificate itself or via the HTTP CA certificate fingerprint.

The generated root CA certificate can be found in the certs directory in your Elasticsearch config location ($ES_CONF_PATH/certs/http_ca.crt). If you’re running Elasticsearch in Docker there is additional documentation for retrieving the CA certificate.

Once you have the http_ca.crt file somewhere accessible pass the content of the file to the client via CACert:

cert, _ := os.ReadFile("/path/to/http_ca.crt")

cfg := elasticsearch.Config{
        Addresses: []string{
            "https://localhost:9200",
        },
        Username: "elastic",
        Password: ELASTIC_PASSWORD
        CACert:   cert
}
es, err := elasticsearch.NewClient(cfg)

This method of verifying the HTTPS connection takes advantage of the certificate fingerprint value noted down earlier. Take this SHA256 fingerprint value and pass it to the Go Elasticsearch client via ca_fingerprint:

cfg := elasticsearch.Config{
        Addresses: []string{
            "https://localhost:9200",
        },
        Username: "elastic",
        Password: ELASTIC_PASSWORD
        CertificateFingerprint: CERT_FINGERPRINT
}
es, err := elasticsearch.NewClient(cfg)

The certificate fingerprint can be calculated using openssl x509 with the certificate file:

openssl x509 -fingerprint -sha256 -noout -in /path/to/http_ca.crt

If you don’t have access to the generated CA file from Elasticsearch you can use the following script to output the root CA fingerprint of the Elasticsearch instance with openssl s_client:

# Replace the values of 'localhost' and '9200' to the
# corresponding host and port values for the cluster.
openssl s_client -connect localhost:9200 -servername localhost -showcerts </dev/null 2>/dev/null \
  | openssl x509 -fingerprint -sha256 -noout -in /dev/stdin

The output of openssl x509 will look something like this:

SHA256 Fingerprint=A5:2D:D9:35:11:E8:C6:04:5E:21:F1:66:54:B7:7C:9E:E0:F3:4A:EA:26:D9:F4:03:20:B5:31:C4:74:67:62:28

If your cluster is configured with security explicitly disabled then you can connect via HTTP:

cfg := elasticsearch.Config{
        Addresses: []string{
            "http://localhost:9200",
        },
}
es, err := elasticsearch.NewClient(cfg)

The Go Elasticsearch client supports sending API requests to multiple nodes in the cluster. This means that work will be more evenly spread across the cluster instead of hammering the same node over and over with requests. To configure the client with multiple nodes you can pass a list of URLs, each URL will be used as a separate node in the pool.

cfg := elasticsearch.Config{
  Addresses: []string{
    "https://localhost:9200",
    "https://localhost:9201",
  },
  CACert:   caCert,
  Username: "elastic",
  Password: ELASTIC_PASSWORD,
}
es, err := elasticsearch.NewClient(cfg)

By default nodes are selected using round-robin, but alternate node selection strategies can be implemented via the elastictransport.Selector interface and provided to the client configuration.

This section contains code snippets to show you how to authenticate with Elasticsearch.

To set the cluster endpoints, the username, and the password programatically, pass a configuration object to the elasticsearch.NewClient() function.

cfg := elasticsearch.Config{
  Addresses: []string{
    "https://localhost:9200",
    "https://localhost:9201",
  },
  Username: "foo",
  Password: "bar",
}
es, err := elasticsearch.NewClient(cfg)

You can also include the username and password in the endpoint URL:

'https://username:password@localhost:9200'

HTTP Bearer authentication uses the ServiceToken parameter by passing the token as a string. This authentication method is used by Service Account Tokens and Bearer Tokens.

cfg := elasticsearch.Config{
    Addresses: []string{
        "https://localhost:9200",
    },
    ServiceToken: "token-value",
}
es, err := elasticsearch.NewClient(cfg)

The Elasticsearch server version 8.0 is introducing a new compatibility mode that allows you a smoother upgrade experience from 7 to 8. In a nutshell, you can use the latest 7.x go-elasticsearch Elasticsearch client with an 8.x Elasticsearch server, giving more room to coordinate the upgrade of your codebase to the next major version.

If you want to leverage this functionality, please make sure that you are using the latest 7.x go-elasticsearch client and set the environment variable ELASTIC_CLIENT_APIVERSIONING to true or the configuration option config.EnableCompatibilityMode in the client Config. The client is handling the rest internally. For every 8.0 and beyond go-elasticsearch client, you’re all set! The compatibility mode is enabled by default.

The Elasticsearch package ties together two separate packages for calling the Elasticsearch APIs and transferring data over HTTP: esapi and estransport, respectively.

Use the elasticsearch.NewDefaultClient() function to create the client with the default settings.

es, err := elasticsearch.NewDefaultClient()
if err != nil {
  log.Fatalf("Error creating the client: %s", err)
}

res, err := es.Info()
if err != nil {
  log.Fatalf("Error getting response: %s", err)
}

defer res.Body.Close()
log.Println(res)

This section illustrates the best practices for leveraging the Elasticsearch client in a Function-as-a-Service (FaaS) environment. The most influential optimization is to initialize the client outside of the function, the global scope. This practice does not only improve performance but also enables background functionality as – for example – sniffing. The following examples provide a skeleton for the best practices.

package httpexample

import (
	"github.com/elastic/go-elasticsearch/v8"
)

var client *elasticsearch.Client

func init() {
	var err error

	... # Client configuration
	client, err = elasticsearch.NewClient(cfg)
	if err != nil {
		log.Fatalf("elasticsearch.NewClient: %v", err)
	}
}

func HttpExample(w http.ResponseWriter, r *http.Request) {
	... # Client usage
}

package httpexample

import (
	"github.com/aws/aws-lambda-go/lambda"
	"github.com/elastic/go-elasticsearch/v8"
)

var client *elasticsearch.Client

func init() {
	var err error

	... # Client configuration
	client, err = elasticsearch.NewClient(cfg)
	if err != nil {
		log.Fatalf("elasticsearch.NewClient: %v", err)
	}
}

func HttpExample() {
	... # Client usage
}

func main() {
	lambda.Start(HttpExample)
}

Resources used to assess these recommendations: