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

A global module with commons utilities for microservice support

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


let defaults = {
  "hystrix.execution.timeoutInMilliseconds": 30000,
  "hystrix.force.circuit.open": false,
  "hystrix.force.circuit.closed": false,
  "hystrix.circuit.sleepWindowInMilliseconds": 3000,
  "hystrix.circuit.errorThresholdPercentage": 50,
  "hystrix.circuit.volumeThreshold": 10,
  "hystrix.metrics.statistical.window.timeInMilliseconds": 10000,
  "hystrix.metrics.statistical.window.bucketsNumber": 10,
  "hystrix.metrics.percentile.window.timeInMilliseconds": 10000,
  "hystrix.metrics.percentile.window.bucketsNumber": 10,
  "hystrix.request.volume.rejectionThreshold": 0,
};

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 || defaults["hystrix.execution.timeoutInMilliseconds"];
  const CIRCUIT_VOLUME_THRESHOLD = configs.circuitVolumeThreshold || defaults["hystrix.circuit.volumeThreshold"];
  const CIRCUIT_SLEEP_WINDOW_IN_MS = configs.circuitSleepWindowInMilliseconds || defaults["hystrix.circuit.sleepWindowInMilliseconds"];
  const REQUEST_VOLUME_REJECTION_THRESHOLD = configs.requestVolumeRejectionThreshold || defaults["hystrix.request.volume.rejectionThreshold"];
  const FORCE_CIRCUIT_OPEN = configs.forceCircuitOpen || defaults["hystrix.force.circuit.open"];
  const FORCE_CIRCUIT_CLOSED = configs.forceCircuitClosed || defaults["hystrix.force.circuit.closed"];
  const STATISTICAL_WINDOW_NUMBER_OF_BUCKETS = configs.statisticalWindowNumberOfBuckets || defaults["hystrix.metrics.statistical.window.bucketsNumber"];
  const STATISTICAL_WINDOW_LENGTH = configs.statisticalWindowLength || defaults["hystrix.metrics.statistical.window.timeInMilliseconds"];
  const PERCENTILE_WINDOW_NUMBER_OF_BUCKETS = configs.percentileWindowNumberOfBuckets || defaults["hystrix.metrics.percentile.window.bucketsNumber"];
  const PERCENTILE_WINDOW_LENGTH = configs.percentileWindowLength || defaults["hystrix.metrics.percentile.window.timeInMilliseconds"];
  const CIRCUIT_ERROR_THRESHOLD_PERCENTAGE = configs.errorThresholdPercentage || defaults["hystrix.circuit.errorThresholdPercentage"];
  CommandFactory.resetCache();
  if (errorHandler) {
    return CommandFactory.getOrCreate(commandKey)
      .timeout(TIMEOUT)
      .circuitBreakerSleepWindowInMilliseconds(CIRCUIT_SLEEP_WINDOW_IN_MS)
      .circuitBreakerRequestVolumeThreshold(CIRCUIT_VOLUME_THRESHOLD)
      .requestVolumeRejectionThreshold(REQUEST_VOLUME_REJECTION_THRESHOLD)
      .circuitBreakerForceOpened(FORCE_CIRCUIT_OPEN)
      .circuitBreakerForceClosed(FORCE_CIRCUIT_CLOSED)
      .statisticalWindowNumberOfBuckets(STATISTICAL_WINDOW_NUMBER_OF_BUCKETS)
      .statisticalWindowLength(STATISTICAL_WINDOW_LENGTH)
      .percentileWindowNumberOfBuckets(PERCENTILE_WINDOW_NUMBER_OF_BUCKETS)
      .percentileWindowLength(PERCENTILE_WINDOW_LENGTH)
      .circuitBreakerErrorThresholdPercentage(CIRCUIT_ERROR_THRESHOLD_PERCENTAGE)
      .run(makeRequest)
      .fallbackTo(fallbackTo)
      .errorHandler(errorHandler)
      .build();
  } else {
    return CommandFactory.getOrCreate(commandKey)
      .timeout(TIMEOUT)
      .circuitBreakerSleepWindowInMilliseconds(CIRCUIT_SLEEP_WINDOW_IN_MS)
      .circuitBreakerRequestVolumeThreshold(CIRCUIT_VOLUME_THRESHOLD)
      .requestVolumeRejectionThreshold(REQUEST_VOLUME_REJECTION_THRESHOLD)
      .circuitBreakerForceOpened(FORCE_CIRCUIT_OPEN)
      .circuitBreakerForceClosed(FORCE_CIRCUIT_CLOSED)
      .statisticalWindowNumberOfBuckets(STATISTICAL_WINDOW_NUMBER_OF_BUCKETS)
      .statisticalWindowLength(STATISTICAL_WINDOW_LENGTH)
      .percentileWindowNumberOfBuckets(PERCENTILE_WINDOW_NUMBER_OF_BUCKETS)
      .percentileWindowLength(PERCENTILE_WINDOW_LENGTH)
      .circuitBreakerErrorThresholdPercentage(CIRCUIT_ERROR_THRESHOLD_PERCENTAGE)
      .run(makeRequest)
      .fallbackTo(fallbackTo)
      .build();
  }
};

module.exports = {
  commandBuilder,
  stream,
};