CircuitBreaker middlewares

Initial configuration

To begin using the circuit-breaker middlewares, you'll need to create and configure a CircuitBreakerFactory instance:

./samples/circuit-breaker.ts

import { CircuitBreakerFactory } from "eridu-tech/circuit-breaker";
import { DatabaseCircuitBreakerAdapter } from "eridu-tech/circuit-breaker/database-circuit-breaker-adapter";
import { MemoryCircuitBreakerStorageAdapter } from "eridu-tech/circuit-breaker/memory-circuit-breaker-storage-adapter";

export const circuitBreakerFactory = new CircuitBreakerFactory({
    adapter: new DatabaseCircuitBreakerAdapter({
        adapter: new MemoryCircuitBreakerStorageAdapter(),
    }),
});

withCircuitBreakerFactory middleware

The CircuitBreaker middleware wraps function calls with a circuit-breaker, providing fault tolerance for distributed systems. Each unique key (derived from the function's arguments) gets its own circuit instance. When the circuit is open, the wrapped function is not called and an error is thrown instead, preventing cascading failures.

Usage

./samples/with-circuit-breaker.ts

import { withCircuitBreakerFactory } from "eridu-tech/circuit-breaker/middlewares";
import { use } from "eridu-tech/middleware";
import { circuitBreakerFactory } from "./circuit-breaker.js";

const withCircuitBreaker = withCircuitBreakerFactory(circuitBreakerFactory);

const callExternalApi = async (endpoint: string): Promise<unknown> => {
    const response = await fetch(`https://api.example.com/${endpoint}`);
    return response.json();
};

// Wrap with circuit-breaker
const protectedCall = use(
    callExternalApi,
    withCircuitBreaker({
        key: ([endpoint]) => `api:${endpoint}`,
    }),
);

await protectedCall("users"); // Succeeds or opens the circuit on repeated failures

info

Here is a complete list of settings for the withCircuitBreaker function.

Settings

Option	Type	Description
key	Invocable<TParameters, string>	A function that produces a unique identifier for the circuit from the wrapped function's arguments. Each unique key gets its own circuit state
errorPolicy	ErrorPolicy	Determines which errors count toward opening the circuit. Defaults to treating all errors as failures
trigger	CircuitBreakerTrigger	Optional custom trigger that determines when the circuit should open. Defaults to the built-in trigger
slowCallTime	ITimeSpan	Optional duration above which a call is considered slow. Exceeding it counts toward opening the circuit (if configured in the trigger)

Further information

For further information refer to eridu-tech/circuit-breaker API docs.