Include request variables in demand control scoring

[tninesling]

We're missing variable support in demand control scoring, so they're currently not counted. Additionally, they don't get passed through to the list size directive, which prevents users from using variables as slicing arguments. This change includes the request variables in context extensions so they can be accessed from the demand control plugin pipeline.

This includes a small refactor to wrap some of the common scoring arguments (schema, request document, etc) into a scoring context to reduce the number of arguments to each function.

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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

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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

• 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

[tninesling]

Is there a better way to do this conversion? This inner n is private so it's not so easy to cleanly convert it to the underlying numeric type.

[BrynCooke]

An alternative is:

            Value::Number(n) if n.is_f64() => {
                apollo_compiler::ast::Value::Float(n.as_f64().expect("is float").into())
            }

            Value::Number(n) => {
                apollo_compiler::ast::Value::Int((n.as_i64().expect("is int") as i32).into())
            }

[tninesling]

This is going to insert an entry of type Map<ByteString, Value> into the context. This type is used both for graphql request variables and graphql response extensions. Should we create some wrapper type to make sure it's disambiguated in context?

[BrynCooke]

Hmm, I'm not sure about doing this. Gonna take a look and see if there is something better.

[BrynCooke]

Yeah, I agree that a wrapper type needs to be used. Maybe also include cost strategy in it so there is just one entry?

I spent a bit of time trying to figure out why we need variables for the response. This is because input fields can have a cost directive right?

[tninesling]

Yes, we need to include argument cost for a field when scoring responses, and we can't score arguments purely from the schema because we may over/under count optional fields.

[BrynCooke]

Needs a wrapper for variables in context.