RateLimiter middlewares

Initial configuration

To begin using the rate-limiter middlewares, you'll need to create and configure a RateLimiterFactory instance:

./samples/rate-limiter.ts

import { RateLimiterFactory } from "eridu-tech/rate-limiter";
import { DatabaseRateLimiterAdapter } from "eridu-tech/rate-limiter/database-rate-limiter-adapter";
import { MemoryRateLimiterStorageAdapter } from "eridu-tech/rate-limiter/memory-rate-limiter-storage-adapter";

export const rateLimiterFactory = new RateLimiterFactory({
    adapter: new DatabaseRateLimiterAdapter({
        adapter: new MemoryRateLimiterStorageAdapter(),
    }),
});

withRateLimiterFactory middleware

The RateLimiter middleware wraps function calls with a rate limiter, controlling how many times a function can be invoked within a configured policy window. Each unique key (derived from the function's arguments) gets its own rate limit counter. Once the limit is reached, further invocations are blocked until the policy permits attempts again.

Usage

./samples/with-rate-limiter.ts

import { withRateLimiterFactory } from "eridu-tech/rate-limiter/middlewares";
import { use } from "eridu-tech/middleware";
import { rateLimiterFactory } from "./rate-limiter.js";

const withRateLimiter = withRateLimiterFactory(rateLimiterFactory);

const fetchHandler = async (request: Request): Promise<Response> => {
    // ... handle the request
    return new Response("OK");
};

// Wrap with rate limiter — max 10 calls per window
const rateLimitedCall = use(
    fetchHandler,
    withRateLimiter({
        key: ([req]) => `api:${String(req.headers.get("x-ip"))}`,
        limit: 10,
    }),
);

await rateLimitedCall(
    new Request("/url", {
        method: "POST",
    }),
);

info

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

Settings

Option	Type	Description
key	Invocable<TParameters, string>	A function that produces the rate-limiter key from the wrapped function's arguments. Each unique key gets its own rate-limit counter
limit	number	Maximum number of invocations allowed within the configured window
onlyError	boolean	When true, only failed (errored) invocations count toward the rate limit. Defaults to false
errorPolicy	ErrorPolicy	Determines which errors count toward the rate limit. Defaults to treating all errors as failures

Further information

For further information refer to eridu-tech/rate-limiter API docs.