Ensure that batch entry contexts are correctly preserved

[garypen]

Batch processing was not using contexts correctly. A representative context was chosen, the first item in a batch of items, and used to provide context functionality for all the generated responses.

The router now correctly preserves request contexts and uses them during response creation.

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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

I've enhanced the existing it_assembles_batch test to ensure that output contexts match input contexts. This isn't fully testing all the new functionality, but along with manual testing, it does mean that the fix is fully tested.

Manual testing was performed by modifying the router to make Context id externally visible and then running a custom test program which updated context in Subgraph and Supergraph stages and ensuring that Context ids were correct.

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

• 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
• const - Basic stress test that runs with a constant number of users

[bnjjj]

Maybe a dumb question but are we sure the ordering of graphql requests is the same and so it's safe to use a Vec instead of a map or something ?
Also could you add tests please ?

[garypen]

Maybe a dumb question but are we sure the ordering of graphql requests is the same and so it's safe to use a Vec instead of a map or something ? Also could you add tests please ?

We are sure (Or at least I am). I did some manual testing to make sure that the ordering was correct. I should have documented that.

Adding tests is challenging, but I'll see what I can think of.

[garypen]

I've enhanced an existing unit test and documented the manual testing that I performed.