@mojaloop/central-services-stream/src/kafka/examples/consumer.js

Streaming library code for central services.

/*****
 License
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 Copyright © 2020-2025 Mojaloop Foundation
 The Mojaloop files are made available by the Mojaloop Foundation under the Apache License, Version 2.0 (the "License") and you may not use these files except in compliance with the License. You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, the Mojaloop files are distributed on an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the specific language governing permissions and limitations under the License.

 Contributors
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 This is the official list of the Mojaloop project contributors for this file.
 Names of the original copyright holders (individuals or organizations)
 should be listed with a '*' in the first column. People who have
 contributed from an organization can be listed under the organization
 that actually holds the copyright for their contributions (see the
 Mojaloop Foundation for an example). Those individuals should have
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 * Mojaloop Foundation
 - Name Surname <name.surname@mojaloop.io>

 * Lazola Lucas <lazola.lucas@modusbox.com>
 * Rajiv Mothilal <rajiv.mothilal@modusbox.com>
 * Miguel de Barros <miguel.debarros@modusbox.com>

 --------------
 ******/

'use strict'

const Consumer = require('../').Consumer
const ConsumerEnums = require('../').Consumer.ENUMS
const Logger = require('@mojaloop/central-services-logger')

const testConsumer = async () => {
  console.log('Instantiate consumer')
  const c = new Consumer(['test'], {
    options: {
      mode: ConsumerEnums.CONSUMER_MODES.recursive,
      batchSize: 1,
      recursiveTimeout: 100,
      messageCharset: 'utf8',
      messageAsJSON: true,
      sync: true,
      consumeTimeout: 1000
    },
    rdkafkaConf: {
      'group.id': 'kafka',
      'metadata.broker.list': 'localhost:9092',
      'enable.auto.commit': false
    },
    topicConf: {},
    logger: Logger
  })

  console.log('Connect consumer')
  const connectionResult = await c.connect()

  console.log(`Connected result=${connectionResult}`)

  console.log('Consume messages')

  c.consume((error, message) => {
    return new Promise((resolve, reject) => {
      if (error) {
        console.log(`WTDSDSD!!! error ${error}`)
        // resolve(false)
        reject(error)
      }
      if (message) { // check if there is a valid message coming back
        console.log(`Message Received by callback function - ${JSON.stringify(message)}`)
        // lets check if we have received a batch of messages or single. This is dependant on the Consumer Mode
        if (Array.isArray(message) && message.length != null && message.length > 0) {
          message.forEach(msg => {
            c.commitMessage(msg)
          })
        } else {
          c.commitMessage(message)
        }
        resolve(true)
      } else {
        resolve(false)
      }
      // resolve(true)
    })
  })

  // consume 'ready' event
  c.on('ready', arg => console.log(`onReady: ${JSON.stringify(arg)}`))
  // consume 'message' event
  c.on('message', message => console.log(`onMessage: ${message.offset}, ${JSON.stringify(message.value)}`))
  // consume 'batch' event
  c.on('batch', message => console.log(`onBatch: ${JSON.stringify(message)}`))

  console.log('testConsumer::end')
}

testConsumer()