microservice-support-stack/lib/core/hystrix.js

A global module with commons utilities to support for microservices

const {
	hystrixSSEStream: HystrixStream,
	commandFactory: CommandFactory
} = require('hystrixjs');
const logger = require('./logger');

const stream = (request, response) => {
  logger.info('Starting hystrix stream...');

  response.append('Content-Type', 'text/event-stream;charset=UTF-8');
  response.append('Cache-Control', 'no-cache, no-store, max-age=0, must-revalidate');
  response.append('Pragma', 'no-cache');

  return HystrixStream.toObservable().subscribe(
    sseData => response.write('data: ' + sseData + '\n\n'),
    err => console.error(err),
    () => response.end()
  );
};

const commandBuilder = (makeRequest, fallbackTo, errorHandler, serviceName, commandKey, configs = {}) => {
  const TIMEOUT = configs.timeout || 3000;
  const STATISTICAL_WINDOW_LENGTH = configs.statisticalWindowLength || 10000;
  const STATISTICAL_WINDOW_NUMBER_OF_BUCKETS = configs.statisticalWindowNumberOfBuckets || 10;
  CommandFactory.resetCache();
  if (errorHandler) {
    return CommandFactory.getOrCreate(commandKey)
      .run(makeRequest)
      .timeout(TIMEOUT)
      .fallbackTo(fallbackTo)
      .statisticalWindowLength(STATISTICAL_WINDOW_LENGTH)
      .statisticalWindowNumberOfBuckets(STATISTICAL_WINDOW_NUMBER_OF_BUCKETS)
      .errorHandler(errorHandler)
      .build();
  } else {
    return CommandFactory.getOrCreate(commandKey)
      .run(makeRequest)
      .timeout(TIMEOUT)
      .fallbackTo(fallbackTo)
      .statisticalWindowLength(STATISTICAL_WINDOW_LENGTH)
      .statisticalWindowNumberOfBuckets(STATISTICAL_WINDOW_NUMBER_OF_BUCKETS)
      .build();
  }
};


module.exports = {
  commandBuilder,
  stream,
};