@node-idempotency/express

#### @node-idempotency/express

An Express middleware that makes requests idempotent
Implements @node-idempotency/core as express middleware.

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#### Why?

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Network requests are unpredictable; clients/proxies may send duplicate or concurrent requests due to retries or network issues. To ensure smooth operation, servers must process each request only once. This package detects and handles duplicates, preventing issues like double charging the customer. It's:

- Race Condition free: Ensures consistent behavior even during concurrent requests.
- Modular: Easily integrates with your storage or existing implementation.(as simple as registering a middleware)
- Customizable: options to tweak the library as per your need.
- RFC compliant: Adheres to standards for compatibility with other systems/clients.

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#### How?

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##### instal

``bash
npm i @node-idempotency/express
`

##### usage

`ts
import * as express from "express";

//server.ts
export default async (): Promise => {
const app = express();
const middleware = await idempotencyAsMiddleware({
storage:{
adapter: StorageAdapterEnum.memory
options: ...adapterOptions
},
...idempotencyOptions
});
app.use(middleware);
//register routes here
app.use(errorHandler); //your custom error handler

return app;
};
`

- storage.adapter can either be memory, redis or an instance of Storage interface.
- storage.options are options to the storage client, required for redis, is client options of redis client.
- idempotencyOptions are the IdempotencyOptions passed to @node-idempotency/core/Idempotency`