add metrics tracking the V8 heap usage

[Geal]

This adds new gauge metrics tracking V8 memory usage:

• apollo.router.v8.heap.used
• apollo.router.v8.heap.total

This uses code introduced in the router-bridge in apollographql/federation-rs#558

Due to the way we release the router-bridge, this updates the federation version to 2.8.3

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ROUTER-671
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

Exceptions

Note any exceptions here

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. ↩

[router-perf]

CI performance tests

• 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

[shorgi]

docs LGTM

[BrynCooke]

Looks great.
@shorgi Could we look at separately creating some sort of troubleshooting docs that talk about when this is useful?

[bnjjj]

Could you also set a unit. Sometimes in some apms it's required to display the metrics properly

[bnjjj]

Same for the unit

[bnjjj]

I know it existed before but could you add description and unit please ?

[Geal]

what kind of unit do we set here? Is there a convention for the expected units in otel?

[Geal]

(asking because I don't see many examples of setting units in our metrics)

[bnjjj]

Yes there are. At different places but for example for memory you can find an example here https://opentelemetry.io/docs/specs/semconv/system/hardware-metrics/#hwmemory---memory-module-metrics and more generally you can take examples from here there are some conventions too

[bnjjj]

For this on I would suggest using query

[Geal]

done

[Geal]

@bnjjj is that the correct way to set units? 9e710a5

[bnjjj]

@Geal yes except that for bytes it's usually By Check example here

[Geal]

@bnjjj ok, it's fixed!