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index.js
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index.js
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'use strict'
const cls = require('cls-hooked')
const uuidv4 = require('uuid/v4')
// generate a unique value for namespace
const nsid = `rtracer:${uuidv4()}`
const ns = cls.createNamespace(nsid)
/**
* Generates a request tracer middleware for Express.
* @param {Object} options possible options
* @param {boolean} options.useHeader respect request header flag
* (default: `false`)
* @param {string} options.headerName request header name, used if `useHeader` is set to `true`
* (default: `X-Request-Id`)
*/
const expressMiddleware = ({
useHeader = false,
headerName = 'X-Request-Id'
} = {}) => {
return (req, res, next) => {
ns.bindEmitter(req)
ns.bindEmitter(res)
let requestId
if (useHeader) {
requestId = req.headers[headerName.toLowerCase()]
}
requestId = requestId || uuidv4()
ns.run(() => {
ns.set('requestId', requestId)
next()
})
}
}
/**
* Generates a request tracer middleware for Koa.
* @param {Object} options possible options
* @param {boolean} options.useHeader respect request header flag
* (default: `false`)
* @param {string} options.headerName request header name, used if `useHeader` is set to `true`
* (default: `X-Request-Id`)
*/
const koaMiddleware = ({
useHeader = false,
headerName = 'X-Request-Id'
} = {}) => {
return (ctx, next) => {
let requestId
if (useHeader) {
requestId = ctx.request.headers[headerName.toLowerCase()]
}
requestId = requestId || uuidv4()
return new Promise(ns.bind((resolve, reject) => {
ns.bindEmitter(ctx.req)
ns.bindEmitter(ctx.res)
ns.set('requestId', requestId)
return next().then(resolve).catch(reject)
}))
}
}
/**
* Returns request tracer id or `undefined` in case if the call is made from an outside CLS context.
*/
const id = () => ns.get('requestId')
module.exports = {
expressMiddleware,
koaMiddleware,
id
}