add support of chunk responses for selectors and instrument in telemetry

[bnjjj]

Giving the ability to compute new attributes everytime we receive a new event in supergraph response. Would be really helpful to create observability for subscriptions and defer.

I also added the support of on_error for selectors and especially error selector I added for every services. Which will let you create some metrics,events or span attributes containing error message. By adding this we will now have to ability to create a counter of request timed out for subgraphs for example:

telemetry:
  instrumentation:
    instruments:
      subgraph:
        requests.timeout:
          value: unit
          type: counter
          unit: request
          description: "subgraph requests containing subgraph timeout"
          attributes:
            subgraph.name: true
          condition:
            eq:
              - "request timed out"
              - error: reason

And thanks to the event support for selectors you'll be able to fetch data directly from the supergraph response body:

telemetry:
  instrumentation:
    instruments:
      acme.request.on_graphql_error:
        value: event_unit
        type: counter
        unit: error
        description: my description
        condition:
          eq:
          - MY_ERROR_CODE
          - response_errors: "$.[0].extensions.code"
        attributes:
          response_errors:
            response_errors: "$.*"

Fixes #5027 #4830

---

Checklist

Complete the checklist (and note appropriate exceptions) before the PR is marked ready-for-review.

• [x] Changes are compatible[^1]
• [x] Documentation[^2] completed
• [ ] Performance impact assessed and acceptable
• Tests added and passing[^3]
  • [x] Unit Tests
  • [x] Integration Tests
  • [x] Manual Tests

Exceptions

Note any exceptions here

Notes

[^1]: It may be appropriate to bring upcoming changes to the attention of other (impacted) groups. Please endeavour to do this before seeking PR approval. The mechanism for doing this will vary considerably, so use your judgement as to how and when to do this. [^2]: Configuration is an important part of many changes. Where applicable please try to document configuration examples. [^3]: Tick whichever testing boxes are applicable. If you are adding Manual Tests, please document the manual testing (extensively) in the Exceptions.

[github-actions[bot]]

@bnjjj, please consider creating a changeset entry in /.changesets/. These instructions describe the process and tooling.

[router-perf[bot]]

CI performance tests

• [x] step - Basic stress test that steps up the number of users over time
• [ ] events_big_cap_high_rate_callback - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity using callback mode
• [ ] large-request - Stress test with a 1 MB request payload
• [ ] events - Stress test for events with a lot of users and deduplication ENABLED
• [ ] xxlarge-request - Stress test with 100 MB request payload
• [ ] events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• [ ] xlarge-request - Stress test with 10 MB request payload
• [ ] step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• [ ] events_callback - Stress test for events with a lot of users and deduplication ENABLED in callback mode
• [ ] no-graphos - Basic stress test, no GraphOS.
• [ ] reload - Reload test over a long period of time at a constant rate of users
• [ ] events_big_cap_high_rate - Stress test for events with a lot of users, deduplication enabled and high rate event with a big queue capacity
• [ ] events_without_dedup_callback - Stress test for events with a lot of users and deduplication DISABLED using callback mode
• [x] const - Basic stress test that runs with a constant number of users