Add apollo_router_deduplicated_queries_total metric

[andrewmcgivery]

Add apollo_router_deduplicated_queries_total metric so that a platform team can understand the impact of enabling query deduplication in traffic shaping.

Note: I couldn't find any examples of how to do a unit or integration test for this so I did a manual test. I setup a local router with a K6 script that hit a subgraph with an artificially slow response time. I was then able to see this metric appear in my Prometheus metrics endpoint:

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Checklist

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

• Changes are compatible¹
• Documentation² completed
• Performance impact assessed and acceptable
• Tests added and passing³
  • Unit Tests
  • Integration Tests
  • Manual Tests

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Notes

Footnotes

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. ↩

[svc-apollo-docs]

❌ Docs Preview Failed

Error

HttpError: Resource not accessible by personal access token - https://docs.github.com/rest/commits/statuses#create-a-commit-status

[bnjjj]

The hardest part will be to test it now :p

[bnjjj]

Could you use the new macro instead ? Search for u64_counter in the codebase. And use the new conventions with dots. Example apollo.router...

[andrewmcgivery]

@bnjjj done!

[bnjjj]

cc @BrynCooke I need you to have ideas about the name of this metric please

[router-perf]

CI performance tests

• connectors-const - Connectors stress test that runs with a constant number of users
• const - Basic stress test that runs with a constant number of users
• demand-control-instrumented - A copy of the step test, but with demand control monitoring and metrics enabled
• demand-control-uninstrumented - A copy of the step test, but with demand control monitoring enabled
• enhanced-signature - Enhanced signature enabled
• events - Stress test for events with a lot of users and deduplication ENABLED
• 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_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
• events_callback - Stress test for events with a lot of users and deduplication ENABLED in callback mode
• events_without_dedup - Stress test for events with a lot of users and deduplication DISABLED
• events_without_dedup_callback - Stress test for events with a lot of users and deduplication DISABLED using callback mode
• extended-reference-mode - Extended reference mode enabled
• large-request - Stress test with a 1 MB request payload
• no-tracing - Basic stress test, no tracing
• reload - Reload test over a long period of time at a constant rate of users
• step-jemalloc-tuning - Clone of the basic stress test for jemalloc tuning
• step-local-metrics - Field stats that are generated from the router rather than FTV1
• step-with-prometheus - A copy of the step test with the Prometheus metrics exporter enabled
• step - Basic stress test that steps up the number of users over time
• xlarge-request - Stress test with 10 MB request payload
• xxlarge-request - Stress test with 100 MB request payload

[BrynCooke]

This should be apollo.router.deduplicated_queries as the dot indicates nesting.
I do wonder if this should just be an attribute on an existing metric though. For instance:

telemetry:

  instrumentation:
    spans:
      mode: spec_compliant
    instruments:
      subgraph:
        http.client.request.duration: 
          attributes: 
            deduplicated: true

[andrewmcgivery]

Does making it an attribute not make it inconsistent with the existing subscriptions metric?