Managing shared state in Node.js without compromising on data lose and security issues

Backend Call

Backend Call

DB Query

Backend Call

DB Query

Backend Call

Practical Examples

X-request-id

Aspects

Experiments

Cache

Local State

Requirements

Maintain context throughout an async flow

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Ensure accessibility of the context only within the same async flow

Async Flow

Backend �API Call

Backend �API Call

DB Query

Requset

Response

Ideas?

Global Object?

Global Object?

How the event loop works?

How Multi-Threading works?

VS

Thread Local Storage

“If you can’t solve a problem, then there is an easier problem you can solve: find it.”

- George Polya

Multi-Threading in Node?

Multi-Threading in Node?

A new thread for each incoming request

Multi-Threading in Node?

A new thread for each incoming request

Child proccess

Multi-Threading in Node?

A new thread for each incoming request

Child proccess Worker threads

Multi-Threading in Node?

A new thread for each incoming request

Child proccess Worker threads Clusters

“Workers (threads) are useful for performing CPU-intensive JavaScript operations. ��They do not help much with I/O-intensive work. ��The Node.js built-in asynchronous I/O operations are more efficient than Workers can be.”

- docs

Built in Node API

The solution

��

A built-in Node.js API that provides a way of propagating the context of the current async operation through the call chain without the need to explicitly pass it as a function parameter. ��It is similar to thread-local storage in other languages.

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AsyncLocalStorage��

Performance

“While you can create your own implementation on top of the node:async_hooks module, AsyncLocalStorage should be preferred as it is a performant and memory safe implementation that involves significant optimizations that are non-obvious to implement.”

- docs

       async_hooks Performance Analysis

Context Loss

In most cases, AsyncLocalStorage works without issues. In rare situations, the current store is lost in one of the asynchronous operations.��If your code is promise-based there should be no problem otherwise if it is callback-based, it is enough to promisify it with util.promisify() so it starts working with native promises.

Summary

AsyncLocalStorage is the best option for a TLS-like solution to store a local context between an async flow. �

Before using it you should be aware of its pitfalls�

• possible context loss if you have a callback-based API�
• performance impact

Thank You