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Hystrix dashboard

createHystrixStream() serves pipeline metrics in the Hystrix text/event-stream format, for the Hystrix dashboard or Turbine. It is compatible with what opossum-hystrix produces, so a dashboard set up for opossum keeps working after a migration. For anything new, prefer Prometheus or OpenTelemetry: Hystrix has been in maintenance mode for years.

import express from 'express';
import { createHystrixStream } from '@ylcnfrht/resilience/hystrix';


const hystrix = createHystrixStream({ pipelines: ['payments', 'inventory'] });


const app = express();
app.get('/hystrix.stream', hystrix.handler);


// on shutdown:
hystrix.dispose();

Point the dashboard at http://<host>/hystrix.stream. The handler takes any Node (req, res) pair (http.createServer, Express, Koa’s ctx.req/ctx.res): it writes one HystrixCommand object per pipeline every interval, and stops when the request closes.

Options

Section titled “Options”
Option Type Default Description
pipelines string[] required Pipeline names to report, one HystrixCommand each.
group string '@ylcnfrht/resilience' Hystrix command group.
window Duration '10s' Rolling window, Hystrix’s default.
interval Duration '1s' How often the stream writes.
timeProvider TimeProvider system clock, unref’d timers For tests.

The returned object has handler(req, res), commands() (the current HystrixCommand objects, to serve as JSON or log), and dispose(), which stops the telemetry listeners and every open stream.

How the numbers map

Section titled “How the numbers map”

The data comes from createStats plus circuit breaker events. Hystrix’s model (thread pools, a command per call site) doesn’t match a pipeline one to one, so some fields are approximations:

Hystrix field Source
requestCount, errorCount, errorPercentage executions and failed executions in the window.
rollingCountSuccess successful executions.
rollingCountShortCircuited circuit rejections (OnCircuitRejected) in the window.
rollingCountSemaphoreRejected other rejections: bulkhead, rate limit, lock.
rollingCountTimeout OnTimeout events (one per timed-out attempt).
rollingCountFailure failures minus rejections minus timeouts, floored at 0.
rollingCountFallbackSuccess fallbacks.
rollingCountResponsesFromCache, rollingCountCollapsedRequests cache hits, coalesced calls.
latencyExecute, latencyTotal (+ _mean) execution latency percentiles (0, 25, 50, 75, 90, 95, 99, 99.5, 100), rounded to ms; both are the same data.
isCircuitBreakerOpen true while the pipeline’s breaker is open or half-open.
currentConcurrentExecutionCount, rollingMaxConcurrentExecutionCount, thread-pool and other counters always 0.
propertyValue_* fixed values (SEMAPHORE isolation, breaker enabled, the window length).
Section titled “Related”