@sap/cds/lib/srv/middlewares/cds-context.js

SAP Cloud Application Programming Model - CDS for Node.js

const cds = require ('../../index')
const corr_id = 'x-correlation-id'
const crippled_corr_id = 'x-correlationid'
const req_id = 'x-request-id'
const vr_id = 'x-vcap-request-id'
const { uuid } = cds.utils
const { EventContext } = cds

module.exports = () => {
  /** @type { import('express').Handler } */
  return function cds_context (req, res, next) {
    const id = req.headers[corr_id] ??= req.headers[crippled_corr_id] || req.headers[req_id] || req.headers[vr_id] || uuid()
    const ctx = EventContext.for ({ id, http: { req, res } })
    res.set ('X-Correlation-ID', id) // Note: we use capitalized style here as that's common standard in HTTP world
    cds._with (ctx, next)
  }
}