express-als-context
v1.0.3
Published
Get and set request-scoped context anywhere
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Express AsyncLocalStorage Context
Get and set request-scoped context anywhere. It's using a now-stable AsyncLocalStorage. It's heavily inspired by express-http-context, but doesn't suffer from the same memory leak issue that it brought (which was due to cls-hooked
issue)
Support
AsyncLocalStorage supports Node.js from 12.17.0
up.
How to use it
Install: npm install --save express-als-context
Use the middleware immediately before the first middleware that needs to have access to the context.
You won't have access to the context in any middleware .use
d before this one.
var express = require('express');
var httpContext = require('express-als-context');
var app = express();
// Use any third party middleware that does not need access to the context here, e.g.
// app.use(some3rdParty.middleware);
app.use(httpContext.middleware);
// all code from here on has access to the same context for each request
Set values based on the incoming request:
// Example authorization middleware
app.use((req, res, next) => {
userService.getUser(req.get('Authorization'), (err, result) => {
if (err) {
next(err);
} else {
httpContext.set('user', result.user)
next();
}
});
});
You can read the values in the code that doesn't have access to the express's req
object:
var httpContext = require('express-als-context');
// Somewhere deep in the Todo Service
function createTodoItem(title, content, callback) {
var user = httpContext.get('user');
db.insert({ title, content, userId: user.id }, callback);
}