Nodejs cache password#

From there get the Redis host, port, and password you can use later in this tutorial.

Nodejs cache free#

We will be using a free Redis database on RedisLabs, please get your $0 Redis up and running following this guide. It is highly recommended you clone the Quotes API Github repository and start from the master branch to follow along. We will add a new endpoing and caching layer where we will cache the JSON on Redis hosted on Redis Labs. It has a simple endpoint /quotes that gets a list of quotes from the database and renders it as JSON. We will use an existing quotes API application built with Node.js and Postgres database. Given the prerequisites are done, let’s go to what we will be building.

You should read the Node.js Postgres tutorial that explains how the quotes API is built.

An account on Redis Lab will be required, you can get your free account with a 30 MB Redis.

Having an understanding of Javascript callback, promise and Async await will be really helpful.

A basic understanding of how Redis works and its general commands are expected.

You have an understanding of how HTTP generally functions.You are aware of how Node.js and Express js works.Add Redis to the Node.js Express Quotes APIīefore we dive into the demo application and its code, below are some of the things better to know:.In this post, we will see how we can do this by adding a Redis cache to an existing Node.js API that uses the Postgres database.

Nodejs cache code#

Relies on an event emitter to notify the code that is waiting when the lock is released.HTTP responses can be sped up with Node.js and Redis caching.

Uses promises to wait for the release of the lock.

Uses a boolean to keep the locked/unlocked state of the mutex.

His solution (pasted below with original comments): There are some npm libraries that implement some kind of mutex support ( lock, mutex, async-lock) but none of them feel as simple and elegant as Valeri’s code. Looking for an existing solution, I came across an article by Valeri Karpo, “ Mutual Exlusion Patterns with Node.js Promises”, that implemented a mutex using promises and an EventEmitter. The programming model of Node.js enforces to embrace asynchronicity and usually you do not have to worry about mutexes. Mutual exclusionis a property of concurrency control, which is instituted for the purpose of preventing race conditions it is the requirement that one thread of execution never enters its critical section at the same time that another concurrent thread of execution enters its own critical section.Īs far as I’m concerned, Node.js does not have native mutex support. We need to synchronize the cache miss branch and prevent multiple requests to execute the code at the “same” time. If we send two parallel requests this is what happens: Req 1: await get('aKey') Req 2: await get('aKey') Req 1: cache miss Req 1: await for slowAsyncOperation() Req 2: cache miss Req 2: await for slowAsyncOperation() Req 1: await set('aKey', value) Req 2: await set('aKey', value)ĭamn! Each parallel request will try to fetch the value and store it. However, the harsh reality of the asynchronous nature of node.js and the event loop has a nasty surprise for us.