dd-trace/packages/datadog-instrumentations/src/helpers/fetch.js

Datadog APM tracing client for JavaScript

'use strict'

exports.createWrapFetch = function createWrapFetch (Request, ch, onLoad) {
  return function wrapFetch (fetch) {
    if (typeof fetch !== 'function') return fetch

    return function (input, init) {
      if (onLoad) {
        onLoad()
        onLoad = undefined
      }

      if (!ch.start.hasSubscribers) return fetch.apply(this, arguments)

      if (input instanceof Request) {
        const ctx = { req: input }

        return ch.tracePromise(() => fetch.call(this, input, init), ctx)
      }
      const req = new Request(input, init)
      const ctx = { req }

      return ch.tracePromise(() => fetch.call(this, req), ctx)
    }
  }
}