caching-middleware

caching middleware for expressesk backends

Install

npm install caching-middleware --save

See migration guide due to breaking changes from v1 to v2

Usage

This middleware will try to retrieve data via a defined primary method. If no entry was found, it will try to use a fallback method (here you can query against your database). If the fallback method returns a value, the update method will be executed, where you can ideally rehydrate your cache. On the next request the data would be retrieved the from the primary method.

  const cache = require('caching-middleware');
  //const db = ...
  //const memCache = ...
  
  const app = express();
 
  const withUser = cache({
    // returned value will be passed into callback functions
    context: req => ({ userId: req.params.id }),
    resultKey: 'user', //defaults to cacheResult
    primary: ctx => memCache.get(ctx.userId),
    fallback: ctx => db.user.findById(ctx.userId),
    // rehydrate cache
    update: (result, ctx) => memCache.set(ctx.userId, result),
  });
 
  app.get('/user/:id', withUser, (req, res) => {
    res.send(req.user); // req[resultKey]
  });
  

Usecase

You can for example retrieve further information about the requester (user), without targeting the database on each request all over again.

Tests

npm install
npm test

Example App

cd example
npm install
./run.sh or npm start