elastic / go-elasticsearch

https://github.com/elastic/go-elasticsearch

Go
The official Go client for Elasticsearch



go-elasticsearch

The official Go client for Elasticsearch.

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Caveats

We encourage you to try the package in your projects, just keep these caveats in mind, please:

  • This is a work in progress. Not all the planned features, standard in official Elasticsearch clients — retries on failures, auto-discovering nodes, ... — are implemented yet.
  • There are no guarantees on API stability. Though the public APIs have been designed very carefully, they can change in a backwards-incompatible way depending on further exploration and user feedback.
  • The client targets Elasticsearch 7.x. Support for 6.x and 5.x APIs will be added later.

Installation

Install the package with go get:

go get -u github.com/elastic/go-elasticsearch

Or, add the package to your go.mod file:

require github.com/elastic/go-elasticsearch v0.0.0

Or, clone the repository:

git clone https://github.com/elastic/go-elasticsearch.git && cd 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 v0.0.0
END

cat > main.go <<-END
  package main

  import (
    "log"

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

  func main() {
    es, _ := elasticsearch.NewDefaultClient()
    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"
// ...

NOTE: When you export the ELASTICSEARCH_URL environment variable, it will be used as the cluster endpoint.

To configure the client, use the elasticsearch.NewClient() function (the options are for illustrative purposes only).

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

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

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 light wrapper around the response body.

// $ go run _examples/main.go

package main

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

  "github.com/elastic/go-elasticsearch"
  "github.com/elastic/go-elasticsearch/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)
  }
  // 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 version number.
  log.Printf("~~~~~~~> Elasticsearch %s", r["version"].(map[string]interface{})["number"])

  // 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()

      // Set up the request object directly.
      req := esapi.IndexRequest{
        Index:      "test",
        DocumentID: strconv.Itoa(i + 1),
        Body:       strings.NewReader(`{"title" : "` + title + `"}`),
        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
  //
  // Use the helper methods of the client.
  res, err = es.Search(
    es.Search.WithContext(context.Background()),
    es.Search.WithIndex("test"),
    es.Search.WithBody(strings.NewReader(`{"query" : { "match" : { "title" : "test" } }}`)),
    es.Search.WithTrackTotalHits(true),
    es.Search.WithPretty(),
  )
  if err != nil {
    log.Fatalf("ERROR: %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))
}

// ~~~~~~~> Elasticsearch 7.0.0-SNAPSHOT
// [200 OK] updated; version=1
// [200 OK] updated; version=1
// -------------------------------------
// [200 OK] 2 hits; took: 7ms
//  * 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.

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.

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