Elasticsearch Scroll Stream

Elasticsearch Scroll query results as a Node.js Readable Stream.

This module works with the official Elasticsearch nodejs clients:

• @elastic/elasticsearch (new Elasticsearch js API)
• elasticsearch (old Elasticsearch js API)

API

ElasticsearchScrollStream is a Readable Stream, so it supports all the methods of a classic Stream#Readable. In addition it exposes a #close() method to force the stream to stop sourcing from Elasticsearch. When the stream begins to be consumed (starting from the first data event), it will contain an attribute _total that is the total number of matched documents.

Installing

To install the latest released version:

npm install elasticsearch-scroll-stream --save

Usage with the official Elasticsearch js API

Example with a simple query strings query.

const { Client } = require('@elastic/elasticsearch')
const ElasticsearchScrollStream = require('elasticsearch-scroll-stream')

const elasticsearch_client = new Client({ node: 'http://localhost:9200' })

// Create index and add documents here...

// You need to pass the client instance and the query object
// as parameters in the constructor
const es_stream = new ElasticsearchScrollStream(client, {
  index: 'elasticsearch-test-scroll-stream',
  type: 'test-type',
  scroll: '10s',
  size: '50',
  _source: ['name'],
  q: 'name:*',
})

// Pipe the results to other writeble streams..
es_stream.pipe(process.stdout)

es_stream.on('end', function() {
  console.log('End')
})

Example with a simple query strings query, and optional_fields specified (in this case we want _id and _score fields into results).

const { Client } = require('@elastic/elasticsearch')
const ElasticsearchScrollStream = require('elasticsearch-scroll-stream')

const elasticsearch_client = new Client({ node: 'http://localhost:9200' })

// Create index and add documents here...

// You need to pass the client instance and the query object
// as parameters in the constructor
const es_stream = new ElasticsearchScrollStream(client, {
  index: 'elasticsearch-test-scroll-stream',
  type: 'test-type',
  scroll: '10s',
  size: '50',
  _source: ['name'],
  q: 'name:*'
}, ['_id', '_score']); // optional_fields parameter: allowed values are those supported by elasticsearch

// Pipe the results to other writeble streams..
es_stream.pipe(process.stdout)

es_stream.on('end', function() {
  console.log("End")
});

Example with a full request definition using the Elasticsearch Query DSL.

const { Client } = require('@elastic/elasticsearch')
const ElasticsearchScrollStream = require('elasticsearch-scroll-stream')

const elasticsearch_client = new Client({ node: 'http://localhost:9200' })

// Create index and add documents here...

// You need to pass the client instance and the query object
// as parameters in the constructor
const es_stream = new ElasticsearchScrollStream(client, {
  index: 'elasticsearch-test-scroll-stream',
  type: 'test-type',
  scroll: '10s',
  size: '50',
  _source: ['name'],
  body: {
    query: {
      bool: {
        must: [
          {
            query_string: {
              default_field: "_all",
              query: 'name:*'
            }
          }
        ]
      }
    }
  }
});

// Pipe the results to other writeble streams..
es_stream.pipe(process.stdout)

es_stream.on('end', function() {
  console.log("End")
});

Example of using the close() method.

const { Client } = require('@elastic/elasticsearch')
const ElasticsearchScrollStream = require('elasticsearch-scroll-stream')


// Create index and add documents here...

const pageSize = '5'
let stopCounterIndex = (parseInt(pageSize) + 1)
let counter = 0
let current_doc
const elasticsearch_client = new Client({ node: 'http://localhost:9200' })

const es_stream = new ElasticsearchScrollStream(elasticsearch_client, {
  index: 'elasticsearch-test-scroll-stream',
  type: 'test-type',
  scroll: '10s',
  size: pageSize,
  _source: ["name"],
  body: {
    query: {
      bool: {
        must: [
          {
            query_string: {
              default_field: "_all",
              query: 'name:third*'
            }
          }
        ]
      }
    }
  }
}, ['_id', '_score']);

es_stream.on('data', function(data) {
  current_doc = JSON.parse(data.toString())
  if (counter == stopCounterIndex) {
    es_stream.close()
  }
  counter++
});

es_stream.on('end', function() {
  console.log(counter)
});

es_stream.on('error', function(err) {
  console.log(err)
});

See test files for more examples.

Developing

Fork the git repo, clone it, then install the dev dependencies.

cd elasticsearch-scroll-stream
npm install

Make your changes, add tests, then run the tests to make sure nothing broke.

make

NOTE: Tests require an ElasticSearch server running at http://127.0.0.1:9200/. You can spawn a docker container for the purpose with:

docker-compose up -d

which maps host port 127.0.0.1:9200 to container port 9200

LICENSE

The MIT License (MIT)

Copyright (c) 2019 Francesco Valente

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.