node 18 fetch capture

[danilobuerger]

node 18 introduced a native fetch: https://nodejs.org/de/blog/announcements/v18-release-announce/#fetch-experimental
how can we capture this? It seems like captureHTTPsGlobal does not work.

[carolabadeer]

Hello!
It looks like opentelemetry-js introduced instrumentation for the new native fetch in Node a few days ago. The npm package opentelemetry/instrumentation-fetch was released 13 days ago, and the documentation on the opentelemetry-js repo shows an example of how to use this instrumentation! Please keep in mind that this package is experimental and still under active development.

[dreamorosi]

@carolabadeer, what about supporting it in this X-Ray SDK?

At least for now there's no deprecation date and as you pointed out the Otel package is experimental, so what should customer use once Nodejs 18 runtime is released?

[willarmiros]

@dreamorosi to be fair the Node v18 fetch is itself experimental :)

At this time we do not have plans to support instrumenting fetch in the X-Ray SDK, and continue to recommend using OTel for instrumenting Node fetch. We would be open to a PR for this instrumentation with sufficient testing in sdk_contrib.

[JamesKyburz]

Not pretty, and ignoring manual mode.

// reverse engineered from https://github.com/aws/aws-xray-sdk-node/blob/93a4f31de2974c10b25ec317bfadd07aabcc9015/packages/core/lib/patchers/http_p.js
// we don't need to take care of manual mode

function traceFetch() {
  const fetch = globalThis.fetch
  globalThis.fetch = async function (resource, options) {
    const traceHeader =
      resource.headers?.get('X-Amzn-Trace-Id') ?? options?.['X-Amzn-Trace-Id']

    if (!traceHeader) {
      const parent = AWSXRay.resolveSegment()

      if (parent) {
        const url = resource?.url ?? resource
        const method = resource?.method ?? options?.method ?? 'GET'
        const { hostname } = new URL(url)
        const subsegment = parent.notTraced
          ? parent.addNewSubsegmentWithoutSampling(hostname)
          : parent.addNewSubsegment(hostname)
        const root = parent.segment ? parent.segment : parent
        subsegment.namespace = 'remote'

        if (!options) {
          options = {}
        }

        if (!options.headers) {
          options.headers = {}
        }

        options.headers['X-Amzn-Trace-Id'] =
          'Root=' +
          root.trace_id +
          ';Parent=' +
          subsegment.id +
          ';Sampled=' +
          (subsegment.notTraced ? '0' : '1')

        subsegment.http = {
          request: {
            url,
            method
          }
        }

        try {
          const res = await fetch.call(globalThis, resource, options)
          if (res.status === 429) {
            subsegment.addThrottleFlag()
          } else if (!res.ok) {
            subsegment.addErrorFlag()
          }
          const cause = AWSXRay.utils.getCauseTypeFromHttpStatus(res.status)
          if (cause) {
            subsegment[cause] = true
          }
          const contentLength = res.headers.get('content-length')
          subsegment.http.response = {
            status: res.status,
            ...(contentLength && { content_length: contentLength })
          }
          subsegment.close()
          return res
        } catch (err) {
          subsegment.close(err)
          throw err
        }
      }
    }

    return await fetch.call(globalThis, resource, options)
  }
}

[mstykow]

Any progress? Node 20 is entering LTS in October 2023 and fetch is no longer experimental.

[srprash]

Hello. We still don't have any near term plans to support fetch instrumentation in the X-Ray SDK. We recommend to use OpenTelemetry instrumentation if possible.

[WtfJoke]

Any progress? Node 20 is entering LTS in October 2023 and fetch is no longer experimental.

To be fair, it is still considered as experimental in Node 20.

Introduced with Node 17 (optin behind an experimental flag)
Then in Node 18, still experimental, but optout behind a no-experimental flag.

Stable in Node 21 onwards (therefore not yet in Node 20 LTS)

On a side note (my opinion only): Its easy to read it wrong.. and I guess its probably pretty stable on Node 20 when its released as stable in Node 21.

[aripalo]

Considering:

• The feature itself is stable in Node 21
• Node 22 is already released and will become active LTS on 2024-10-29
• Node 22 AWS Lambda Runtime target launch on November 2024

I think it might be good to start the work on supporting fetch with X-Ray SDK sooner rather than later.

[dreamorosi]

They actually already added it as a separate package in the latest release: https://github.com/aws/aws-xray-sdk-node/blob/master/CHANGELOG.md