Any way to reuse default transports but with dynamic request data

[OrkhanAlikhanov]

Hello, we have to send sentry events/traces to the different endpoints in a specific format which dumps those the events to kafka where we pick up them, reconstruct a proper valid envelope payload and post to internal sentry. I know that we can create custom transports for that but that's a pain considering there are a lot of good stuff in createTransport, makeFetchTransport, and makeXHRTransport that we'll have to copy over, just to change the payload format and url/headers. Would be great if we could something like this:

import {makeFetchTransport, makeXHRTransport} from '@sentry/browser'
import {supportsFetch} from '@sentry/utils'

export function makeCustomTransport(options: CustomTransportOptions) {
  const newOptions = {
    ...options,
    getRequest: payload => {
      const body = customSerializeEnvelope(payload.envelope) /// We can use sentry's default serializeEnvelope here too
      const url = isCertainType(payload.envelope) ? certainUrl : payload.url
      const headers = {
        ...payload.headers,
        'x-item-v': '1234',
      }

      return {
        body,
        headers,
        url,
      }
    },
  }

  return supportsFetch()
    ? makeFetchTransport(newOptions)
    : makeXHRTransport(newOptions)
}

Basically getRequest callback is called with certain payload and return value (url, body, and headers) is passed down to the underlaying transport (fetch/xhr in this case). What do you think?

[AbhiPrasad]

You can do something similar to #6211 (comment), but then add the following logic:

const transport = supportsFetch() ? makeFetchTransport(transportOptions) : makeXHRTransport(transportOptions);

[OrkhanAlikhanov]

@AbhiPrasad thanks for the answer but xhrTransport.send(envelope) is still doing its own serialization of envelope. Our requirement is to have totally different request.body format as well as request.url and request.headers while still benefitting from the internal good stuff being done in createTransport, makeFetchTransport, and makeXHRTransport

[lforst]

I sadly don't think that is possible and we don't really have plans to expose the "good stuff" (lol) in the API. The transport code is usually not that much. Maybe you can just vendor it yourself?

[AbhiPrasad]

You can override headers by setting transport options in init: https://docs.sentry.io/platforms/javascript/configuration/options/#transport-options. Both the XHR and fetch transports should respect this.

[OrkhanAlikhanov]

Thanks, I really appreciate the help. Let's forget about url and headers, we are mainly interested in having a totally different serialization format. Something like this #6342 would allow us to provide our own serialization but still utilizing fetch/xhr transport. The PR updates createTransport method which fetch/xhr internally relies on.

[OrkhanAlikhanov]

@AbhiPrasad any thoughts?