Unix socket support for subgraphs

[Geal]

Fix #3504

This implements support for Unix sockets in subgraph connections by specifying URLs in the unix:///path/to/router.sock format.

Implementation details:

• the Uri type used throughout the router does not actually support the unix:// scheme, and there is no real standard for it, so the library we use here hides the socket path by hex encoding it in the authority part of the Uri
• this only supports stream sockets
• decompression is supported
• TLS is not supported

Note: I'd like to add it to the doc but can't decide on the right place to put it. Any suggestions?

TODO:

• [x] update the override_subgraph_url plugin to support it

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Checklist

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

• [ ] Changes are compatible[^1]
• [ ] Documentation[^2] completed
• [ ] Performance impact assessed and acceptable
• Tests added and passing[^3]
  • [ ] Unit Tests
  • [ ] Integration Tests
  • [ ] Manual Tests

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Notes

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[router-perf[bot]]

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
• [x] 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
• [x] step - Basic stress test that steps up the number of users over time

[abernix]

@shorgi Do you have suggestions on where this can land in the docs?

[shorgi]

@shorgi Do you have suggestions on where this can land in the docs?

Is this a new valid routing_url or subgraph_url? And if subgraph_url, can it be set via override_subgraph_urls?

For now in router docs, the Configuration page is the landing page for all user-configurable router settings. We can add content to Subgraph routing URLs or a new heading for Routing URLs.

This also has ramifications for federation, rover, and GraphOS docs. Taking note of this as we reorganize the docs IA.

[Geal]

it is a new subgraph URL, and it will be supported by override_subgraph_url. But also, it could come from the supergraph schema

[Geal]

ok, it's mentioned in the subgraph routing urls section now https://github.com/apollographql/router/pull/4757/files#diff-69d7e3fff212844102e67091fcc275b06d67899a25df2c16f9f5a78bfd7e6444R517

[Geal]

it needs a few more fixes to make sure builds are passing on Windows (where unix sockets don't exist) then I'll merge it