NYPL Streams Client

Helper lib for interacting with the (internal) NYPL Streams

Installation

Install it via npm for use inside your project:

npm i @nypl/nypl-streams-client --save

Usage

const NyplStreamsClient = require('@nypl/nypl-Streams-client')
var streamsClient = new NyplStreamsClient({ nyplDataApiClientBase: 'http://example.com/api/v0.1/' })

Client options include:

• nyplDataApiClientBase: Base URL for the NYPL Data API, as required by NYPL API client base_url. (Alternatively use env NYPL_API_BASE_URL)
• writeBatchSize: Batch size to use when writing records via putRecords. AWS max is 500. Default 500
• recordsPerSecond: Max records to write to stream in a given second through any means. AWS max is 1000. Default 500
• waitBetweenDescribeCallsInSeconds: Delay to insert between successive Describe calls (i.e. when checking stream availability. Default 4
• maxDescribeCallRetries: Maximum number of Describe calls to make before failing. Default 10
• awsRegion: AWS region that your kinesis streams are located in. Default 'us-east-1'
• logLevel: Set log level (i.e. info, error, warn, debug). Default env.LOG_LEVEL or 'error'

streamsClient.write (streamName, data, opts)

Returns a Promise that resolves when the given data has been written to the named stream.

Params:

• streamName: String name of stream to write to. (Also identifies the avro encoding to use.)
• data: An object (or array of objects) to encode and write to the stream
• opts: Optional options hash that may include:
  • avroEncode: Boolean indicating whether or not to avro-encode the data before writing. Default true
  • avroSchemaName: String schema name identifying avro schema to use when encoding data. Defaults to streamName.

To write a single record to a stream (encoded to "MyStream" schema):

streamsClient.write('MyStream', { id: 'id1', field1: 1, field2: 2 }).then((resp) => {
  console.log('Finished writing to stream ' + resp.Records.length)
}).catch((e) => console.error('Error writing to stream: ', e))

To write multiple records to a stream, batched and rate-limited to avoid write errors:

var records = [ { id: 'id1', field1: 1, field2: 2 }, { id: 'id2', field1: 1 }, ... ] // Array of any length
var options = {
  recordsPerSecond: 500 // This is the default and well below the 1000/s AWS constraint
}
streamsClient.write('MyStream', records, options).then((resp) => {
  console.log('Finished writing to stream ' + resp.Records.length)
}).catch((e) => console.error('Error writing to stream: ', e))

Above will resolve after records.length / 500 seconds. The resolved value is a hash merged from the hashes returned from each putRecords call.

streamsClient.decodeData (schemaName, data)

A convenience function for decoding data received from a Kinesis stream (e.g. via a lambda event). Returns a Promise that resolves the record (or array of records) decoded.

Params:

• schemaName: String name of schema the data is encoded in.
• data: An object (or array of objects) to decode.

Example lambda handler with a kinesis trigger:

exports.handler = function (event, context, callback) {
  // Initialize streams client:
  const streamsClient = new NyplStreamsClient({ nyplDataApiClientBase: 'http://example.com/api/v0.1/' })
  const record = event.Records[0]

  if (record.kinesis) {
    const decodedKinesisData = streamsClient.decodeData('SchemaName', event.Records.map(record => record.kinesis.data));

    // Resolve the Promise and do something with the decoded data
    return decodedKinesisData
      .then((result) => console.log('result:', result))
      .catch((err) => console.log('rejected:', err));
  }
}

streamsClient.decodeAvroBufferString (bufferString, avroObject, encodeType = 'base64')

A convenience function for returning a decoded Avro Object from a given encoded Buffer

Params:

• bufferString - String representing encoded buffer.
• avroObject - Avro Object containing fromBuffer method used to decode the bufferString.
• encodeType - String representing type of encoding, defaults to base64. (optional)

Example:

  const avsc = require('avsc')
  // Initialize streams client:
  const streamsClient = new NyplStreamsClient({ nyplDataApiClientBase: 'http://example.com/api/v0.1/' })
  // Using the npm avsc module
  const avroType = avsc.parse(JSON.parse(schema))
  // Encoded buffer string
  const bufferString = 'AEg5MzA4ZDMxMi0zZWQ0LTQ2ZjEtOWJiNS1iN'
  // Result of decoded buffer string
  const decodedBuffer = NyplStreamsClient.decodeAvroBufferString(bufferString, avroType)

Testing

npm test