elasticsearch

README

go-elasticsearch

The official Go client for Elasticsearch.

Compatibility

The client major versions correspond to the compatible Elasticsearch major versions: to connect to Elasticsearch 7.x, use a 7.x version of the client, to connect to Elasticsearch 6.x, use a 6.x version of the client.

When using Go modules, include the version in the import path, and specify either an explicit version or a branch:

require github.com/elastic/go-elasticsearch/v7 7.x
require github.com/elastic/go-elasticsearch/v7 7.0.0

It's possible to use multiple versions of the client in a single project:

// go.mod
github.com/elastic/go-elasticsearch/v6 6.x
github.com/elastic/go-elasticsearch/v7 7.x

// main.go
import (
  elasticsearch6 "github.com/elastic/go-elasticsearch/v6"
  elasticsearch7 "github.com/elastic/go-elasticsearch/v7"
)
// ...
es6, _ := elasticsearch6.NewDefaultClient()
es7, _ := elasticsearch7.NewDefaultClient()

The master branch of the client is compatible with the current master branch of Elasticsearch.

Installation

Add the package to your go.mod file:

require github.com/elastic/go-elasticsearch/v8 master

Or, clone the repository:

git clone --branch master https://github.com/elastic/go-elasticsearch.git $GOPATH/src/github.com/elastic/go-elasticsearch

A complete example:

mkdir my-elasticsearch-app && cd my-elasticsearch-app

cat > go.mod <<-END
  module my-elasticsearch-app

  require github.com/elastic/go-elasticsearch/v8 master
END

cat > main.go <<-END
  package main

  import (
    "log"

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

  func main() {
    es, _ := elasticsearch.NewDefaultClient()
    log.Println(elasticsearch.Version)
    log.Println(es.Info())
  }
END

go run main.go

Usage

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)
}

log.Println(res)

// [200 OK] {
//   "name" : "node-1",
//   "cluster_name" : "go-elasticsearch"
// ...

When you export the ELASTICSEARCH_URL environment variable, it will be used to set the cluster endpoint(s). Separate multiple adresses by a comma.

To set the cluster endpoint(s) programatically, pass them in the configuration object to the elasticsearch.NewClient() function.

cfg := elasticsearch.Config{
  Addresses: []string{
    "http://localhost:9200",
    "http://localhost:9201",
  },
}
es, err := elasticsearch.NewClient(cfg)
// ...

To configure the HTTP settings, pass a http.Transport object in the configuration object (the values are for illustrative purposes only).

cfg := elasticsearch.Config{
  Transport: &http.Transport{
    MaxIdleConnsPerHost:   10,
    ResponseHeaderTimeout: time.Second,
    DialContext:           (&net.Dialer{Timeout: time.Second}).DialContext,
    TLSClientConfig: &tls.Config{
      MinVersion: tls.VersionTLS11,
      // ...
    },
  },
}

es, err := elasticsearch.NewClient(cfg)
// ...

See the _examples/configuration.go and _examples/customization.go files for more examples of configuration and customization of the client.

The following example demonstrates a more complex usage. It fetches the Elasticsearch version from the cluster, indexes a couple of documents concurrently, and prints the search results, using a lightweight wrapper around the response body.

// $ go run _examples/main.go

package main

import (
  "bytes"
  "context"
  "encoding/json"
  "log"
  "strconv"
  "strings"
  "sync"

  "github.com/elastic/go-elasticsearch/v8"
  "github.com/elastic/go-elasticsearch/v8/esapi"
)

func main() {
  log.SetFlags(0)

  var (
    r  map[string]interface{}
    wg sync.WaitGroup
  )

  // Initialize a client with the default settings.
  //
  // An `ELASTICSEARCH_URL` environment variable will be used when exported.
  //
  es, err := elasticsearch.NewDefaultClient()
  if err != nil {
    log.Fatalf("Error creating the client: %s", err)
  }

  // 1. Get cluster info
  //
  res, err := es.Info()
  if err != nil {
    log.Fatalf("Error getting response: %s", err)
  }
  // Check response status
  if res.IsError() {
    log.Fatalf("Error: %s", res.String())
  }
  // Deserialize the response into a map.
  if err := json.NewDecoder(res.Body).Decode(&r); err != nil {
    log.Fatalf("Error parsing the response body: %s", err)
  }
  // Print client and server version numbers.
  log.Printf("Client: %s", elasticsearch.Version)
  log.Printf("Server: %s", r["version"].(map[string]interface{})["number"])
  log.Println(strings.Repeat("~", 37))

  // 2. Index documents concurrently
  //
  for i, title := range []string{"Test One", "Test Two"} {
    wg.Add(1)

    go func(i int, title string) {
      defer wg.Done()

      // Build the request body.
      var b strings.Builder
      b.WriteString(`{"title" : "`)
      b.WriteString(title)
      b.WriteString(`"}`)

      // Set up the request object.
      req := esapi.IndexRequest{
        Index:      "test",
        DocumentID: strconv.Itoa(i + 1),
        Body:       strings.NewReader(b.String()),
        Refresh:    "true",
      }

      // Perform the request with the client.
      res, err := req.Do(context.Background(), es)
      if err != nil {
        log.Fatalf("Error getting response: %s", err)
      }
      defer res.Body.Close()

      if res.IsError() {
        log.Printf("[%s] Error indexing document ID=%d", res.Status(), i+1)
      } else {
        // Deserialize the response into a map.
        var r map[string]interface{}
        if err := json.NewDecoder(res.Body).Decode(&r); err != nil {
          log.Printf("Error parsing the response body: %s", err)
        } else {
          // Print the response status and indexed document version.
          log.Printf("[%s] %s; version=%d", res.Status(), r["result"], int(r["_version"].(float64)))
        }
      }
    }(i, title)
  }
  wg.Wait()

  log.Println(strings.Repeat("-", 37))

  // 3. Search for the indexed documents
  //
  // Build the request body.
  var buf bytes.Buffer
  query := map[string]interface{}{
    "query": map[string]interface{}{
      "match": map[string]interface{}{
        "title": "test",
      },
    },
  }
  if err := json.NewEncoder(&buf).Encode(query); err != nil {
    log.Fatalf("Error encoding query: %s", err)
  }

  // Perform the search request.
  res, err = es.Search(
    es.Search.WithContext(context.Background()),
    es.Search.WithIndex("test"),
    es.Search.WithBody(&buf),
    es.Search.WithTrackTotalHits(true),
    es.Search.WithPretty(),
  )
  if err != nil {
    log.Fatalf("Error getting response: %s", err)
  }
  defer res.Body.Close()

  if res.IsError() {
    var e map[string]interface{}
    if err := json.NewDecoder(res.Body).Decode(&e); err != nil {
      log.Fatalf("Error parsing the response body: %s", err)
    } else {
      // Print the response status and error information.
      log.Fatalf("[%s] %s: %s",
        res.Status(),
        e["error"].(map[string]interface{})["type"],
        e["error"].(map[string]interface{})["reason"],
      )
    }
  }

  if err := json.NewDecoder(res.Body).Decode(&r); err != nil {
    log.Fatalf("Error parsing the response body: %s", err)
  }
  // Print the response status, number of results, and request duration.
  log.Printf(
    "[%s] %d hits; took: %dms",
    res.Status(),
    int(r["hits"].(map[string]interface{})["total"].(map[string]interface{})["value"].(float64)),
    int(r["took"].(float64)),
  )
  // Print the ID and document source for each hit.
  for _, hit := range r["hits"].(map[string]interface{})["hits"].([]interface{}) {
    log.Printf(" * ID=%s, %s", hit.(map[string]interface{})["_id"], hit.(map[string]interface{})["_source"])
  }

  log.Println(strings.Repeat("=", 37))
}

// Client: 8.0.0-SNAPSHOT
// Server: 8.0.0-SNAPSHOT
// ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
// [201 Created] updated; version=1
// [201 Created] updated; version=1
// -------------------------------------
// [200 OK] 2 hits; took: 5ms
//  * ID=1, map[title:Test One]
//  * ID=2, map[title:Test Two]
// =====================================

As you see in the example above, the esapi package allows to call the Elasticsearch APIs in two distinct ways: either by creating a struct, such as IndexRequest, and calling its Do() method by passing it a context and the client, or by calling the Search() function on the client directly, using the option functions such as WithIndex(). See more information and examples in the package documentation.

The estransport package handles the transfer of data to and from Elasticsearch. At the moment, the implementation is really minimal: it only round-robins across the configured cluster endpoints. In future, more features — retrying failed requests, ignoring certain status codes, auto-discovering nodes in the cluster, and so on — will be added.

Helpers

The esutil package provides convenience helpers for working with the client. At the moment, it provides the esutil.JSONReader() helper function.

Examples

The _examples folder contains a number of recipes and comprehensive examples to get you started with the client, including configuration and customization of the client, mocking the transport for unit tests, embedding the client in a custom type, building queries, performing requests, and parsing the responses.

License

(c) 2019 Elasticsearch. Licensed under the Apache License, Version 2.0.

Documentation

Overview

Package elasticsearch provides a Go client for Elasticsearch.

Create the client with the NewDefaultClient function:

elasticsearch.NewDefaultClient()

The ELASTICSEARCH_URL environment variable is used instead of the default URL, when set. Use a comma to separate multiple URLs.

To configure the client, pass a Config object to the NewClient function:

cfg := elasticsearch.Config{
  Addresses: []string{
    "http://localhost:9200",
    "http://localhost:9201",
  },
  Username: "foo",
  Password: "bar",
  Transport: &http.Transport{
    MaxIdleConnsPerHost:   10,
    ResponseHeaderTimeout: time.Second,
    DialContext:           (&net.Dialer{Timeout: time.Second}).DialContext,
    TLSClientConfig: &tls.Config{
      MinVersion:         tls.VersionTLS11,
    },
  },
}

elasticsearch.NewClient(cfg)

When using the Elastic Service (https://elastic.co/cloud), you can use CloudID instead of Addresses. When either Addresses or CloudID is set, the ELASTICSEARCH_URL environment variable is ignored.

See the elasticsearch_integration_test.go file and the _examples folder for more information.

Call the Elasticsearch APIs by invoking the corresponding methods on the client:

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

log.Println(res)

See the github.com/elastic/go-elasticsearch/esapi package for more information about using the API.

See the github.com/elastic/go-elasticsearch/estransport package for more information about configuring the transport.

Index

• Constants
• type Client
  • func NewClient(cfg Config) (*Client, error)
  • func NewDefaultClient() (*Client, error)
  • func (c *Client) DiscoverNodes() error
  • func (c *Client) Metrics() (estransport.Metrics, error)
  • func (c *Client) Perform(req *http.Request) (*http.Response, error)
• type Config

Examples

• NewClient
• NewClient (Logger)
• NewDefaultClient

Constants

const Version = version.Client

Version returns the package version as a string.

Types

type Client

type Client struct {
	*esapi.API // Embeds the API methods
	Transport  estransport.Interface
}

Client represents the Elasticsearch client.

func NewClient

func NewClient(cfg Config) (*Client, error)

NewClient creates a new client with configuration from cfg.

It will use http://localhost:9200 as the default address.

It will use the ELASTICSEARCH_URL environment variable, if set, to configure the addresses; use a comma to separate multiple URLs.

If either cfg.Addresses or cfg.CloudID is set, the ELASTICSEARCH_URL environment variable is ignored.

It's an error to set both cfg.Addresses and cfg.CloudID.

Example

cfg := elasticsearch.Config{
	Addresses: []string{
		"http://localhost:9200",
	},
	Username: "foo",
	Password: "bar",
	Transport: &http.Transport{
		MaxIdleConnsPerHost:   10,
		ResponseHeaderTimeout: time.Second,
		DialContext:           (&net.Dialer{Timeout: time.Second}).DialContext,
		TLSClientConfig: &tls.Config{
			MinVersion: tls.VersionTLS11,
		},
	},
}

es, _ := elasticsearch.NewClient(cfg)
log.Print(es.Transport.(*estransport.Client).URLs())

Example (Logger)

// import "github.com/elastic/go-elasticsearch/v8/estransport"

// Use one of the bundled loggers:
//
// * estransport.TextLogger
// * estransport.ColorLogger
// * estransport.CurlLogger
// * estransport.JSONLogger

cfg := elasticsearch.Config{
	Logger: &estransport.ColorLogger{Output: os.Stdout},
}

elasticsearch.NewClient(cfg)

func NewDefaultClient

func NewDefaultClient() (*Client, error)

NewDefaultClient creates a new client with default options.

It will use http://localhost:9200 as the default address.

It will use the ELASTICSEARCH_URL environment variable, if set, to configure the addresses; use a comma to separate multiple URLs.

Example

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

res, err := es.Info()
if err != nil {
	log.Fatalf("Error getting the response: %s\n", err)
}
defer res.Body.Close()

log.Print(es.Transport.(*estransport.Client).URLs())

func (*Client) DiscoverNodes

func (c *Client) DiscoverNodes() error

DiscoverNodes reloads the client connections by fetching information from the cluster.

func (*Client) Metrics

func (c *Client) Metrics() (estransport.Metrics, error)

Metrics returns the client metrics.

func (*Client) Perform

func (c *Client) Perform(req *http.Request) (*http.Response, error)

Perform delegates to Transport to execute a request and return a response.

type Config

type Config struct {
	Addresses []string // A list of Elasticsearch nodes to use.
	Username  string   // Username for HTTP Basic Authentication.
	Password  string   // Password for HTTP Basic Authentication.

	CloudID string // Endpoint for the Elastic Service (https://elastic.co/cloud).
	APIKey  string // Base64-encoded token for authorization; if set, overrides username and password.

	RetryOnStatus        []int // List of status codes for retry. Default: 502, 503, 504.
	DisableRetry         bool  // Default: false.
	EnableRetryOnTimeout bool  // Default: false.
	MaxRetries           int   // Default: 3.

	DiscoverNodesOnStart  bool          // Discover nodes when initializing the client. Default: false.
	DiscoverNodesInterval time.Duration // Discover nodes periodically. Default: disabled.

	EnableMetrics     bool // Enable the metrics collection.
	EnableDebugLogger bool // Enable the debug logging.

	RetryBackoff func(attempt int) time.Duration // Optional backoff duration. Default: nil.

	Transport http.RoundTripper    // The HTTP transport object.
	Logger    estransport.Logger   // The logger object.
	Selector  estransport.Selector // The selector object.

	// Optional constructor function for a custom ConnectionPool. Default: nil.
	ConnectionPoolFunc func([]*estransport.Connection, estransport.Selector) estransport.ConnectionPool
}

Config represents the client configuration.