@ctx/express
v1.1.0
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Express middlewares using context
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@ctx/express
Middlewares to make using context's easier in Express applications.
See the typedoc for API documentation.
Example
The timeout
middleware attaches a context with a fixed timeout to every
incoming request. We can use this to implement a timeout for our users; if the
context times out, return an error message.
const express = require('express')
const expressCtx = require('@ctx/express')
const context = require('@ctx/context')
const app = express()
app.use(expressCtx.timeout(1000))
app.get('/', async (req, res) => {
try {
const data = await doSomething(req.ctx, req.body)
res.json(data).end()
} catch (err) {
if (err === context.DeadlineExceeded) {
res.status(500).end('timed out')
} else {
res.status(500).end('internal server error')
}
})
})
The addHeader
reads headers from the request object and attaches them to the
context. This can ease some of the burden of passing values down through the
stack. For example,
const express = require('express')
const expressCtx = require('@ctx/express')
const context = require('@ctx/context')
const app = express()
app.use(expressCtx.addHeader(['x-user-id']))
app.get('/', async (req, res) => {
const data = await doSomething(req.ctx, req.body)
res.json(data).end()
})
function doSomething (ctx, body) {
...
const username = getUsername(ctx)
...
}
function getUsername (ctx) {
return usernames[ctx.Value('x-user-id')]
}
Other useful cases for this include passing a "request id" header to downstream services for tracing and distributed logging.