align coprocessor metric creation

[Geal]

There are currently 2 different ways to create metrics, with slight incompatibilities. This makes sure that the execution stage coprocessor metrics are generated in the same way as the other stages

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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

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

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

[BrynCooke]

Sorry, we're trying to move away from the tracing macros for metrics. They cause a bunch of issues around types, they are slow and also they can't be unit tested. Can we move to the new macros?

There's docs for the new macros here: https://github.com/apollographql/router/blob/dev/dev-docs/metrics.md

[Geal]

the issue appeared because I tried to move to the new macros at the exectution stage. Do you want me to update the other stages instead?

[BrynCooke]

Yeah let's try and yeet the other metrics macro use.

It's generally bad form to have multiple points where a metric is updated as with both the macros there is a risk of collision. The only reason it didn't hit us harder is that the old tracing macros didn't fill out the metric descriptions. In other areas of the code we also had issues with double counting.

Ideally we pull out a function that updates the metric and use this in all places in this plugin or alternatively use the regular meter provider to create the meter once and store it in the plugin for reuse at all current callsites.