@zenvark/prom

Prometheus metrics integration for Zenvark Circuit Breaker.

Installation

npm install @zenvark/prom prom-client

Usage

import { CircuitBreaker, ConsecutiveBreaker, ConstantBackoff } from "zenvark";
import { PrometheusBreakerMetrics } from "@zenvark/prom";
import { register } from "prom-client";
import { Redis } from "ioredis";

const redis = new Redis("redis://localhost:6379");

const circuitBreaker = new CircuitBreaker({
  id: "my-service-api",
  redis,
  breaker: new ConsecutiveBreaker({ threshold: 5 }),
  health: {
    backoff: new ConstantBackoff({ delayMs: 5000 }),
    async check(type, signal) {
      const response = await fetch("https://api.example.com/health", {
        signal,
      });
      if (!response.ok) throw new Error("Health check failed");
    },
  },
  metrics: new PrometheusBreakerMetrics({
    register,
    customLabels: { service: "my-api", environment: "production" },
  }),
});

await circuitBreaker.start();

Available Metrics

| Metric | Type | Description | Labels | | -------------------------------------- | --------- | -------------------------------- | ------------------------------ | | zenvark_call_duration_seconds | Histogram | Duration of protected calls | breaker_id, result | | zenvark_blocked_requests_total | Counter | Requests blocked by open circuit | breaker_id | | zenvark_healthcheck_duration_seconds | Histogram | Health check attempt duration | breaker_id, type, result |

Label Values

• breaker_id - Circuit breaker instance identifier
• type - Health check type: recovery or idle
• result - Outcome: success or failure
• Custom labels - Additional key-value pairs from configuration

Custom Labels

Add custom labels to all metrics:

const metrics = new PrometheusBreakerMetrics({
  register,
  customLabels: {
    service: "payment-service",
    environment: "production",
    region: "us-east-1",
  },
});

Documentation

Full documentation: https://zenvark.github.io/zenvark/docs/guides/metrics

For comprehensive information about Zenvark Circuit Breaker:

• Main Documentation
• Metrics & Observability Guide
• GitHub Repository

License

MIT