H-3432: harpc: Expose background task

[indietyp]

🌟 What is the purpose of this PR?

This adds an ergonomic way to spawn and create the background task that's required to operate without leaking memory.

Primarily it makes the use of tokio::sync::broadcast an implementation detail, thought that might make sense, as the user shouldn't care what we use under the hood. It's just a stream of events.

Pre-Merge Checklist 🚀

🚢 Has this modified a publishable library?

This PR:

• does not modify any publishable blocks or libraries, or modifications do not need publishing

📜 Does this require a change to the docs?

The changes in this PR:

• are internal and do not require a docs change

🕸️ Does this require a change to the Turbo Graph?

The changes in this PR:

• do not affect the execution graph

[github-actions]

Benchmark results

@rust/graph-benches – Integrations

representative_read_entity

Function	Value	Mean	Flame graphs
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/organization/v/1	$$16.4 \mathrm{ms} \pm 192 \mathrm{μs}\left({\color{red}22.3 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/book/v/1	$$16.3 \mathrm{ms} \pm 207 \mathrm{μs}\left({\color{gray}1.03 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/page/v/2	$$16.6 \mathrm{ms} \pm 175 \mathrm{μs}\left({\color{lightgreen}-32.377 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/block/v/1	$$16.2 \mathrm{ms} \pm 190 \mathrm{μs}\left({\color{lightgreen}-32.196 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/uk-address/v/1	$$16.1 \mathrm{ms} \pm 179 \mathrm{μs}\left({\color{gray}-1.883 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/playlist/v/1	$$17.9 \mathrm{ms} \pm 201 \mathrm{μs}\left({\color{red}10.5 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/building/v/1	$$16.5 \mathrm{ms} \pm 171 \mathrm{μs}\left({\color{gray}-2.676 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/song/v/1	$$16.0 \mathrm{ms} \pm 197 \mathrm{μs}\left({\color{gray}-1.846 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	entity type ID: https://blockprotocol.org/@alice/types/entity-type/person/v/1	$$16.8 \mathrm{ms} \pm 214 \mathrm{μs}\left({\color{lightgreen}-6.704 \mathrm{\%}}\right) $$	Flame Graph

representative_read_entity_type

Function	Value	Mean	Flame graphs
get_entity_type_by_id	Account ID: d4e16033-c281-4cde-aa35-9085bf2e7579	$$1.41 \mathrm{ms} \pm 6.65 \mathrm{μs}\left({\color{gray}0.821 \mathrm{\%}}\right) $$	Flame Graph

scaling_read_entity_complete_zero_depth

Function	Value	Mean	Flame graphs
entity_by_id	50 entities	$$4.02 \mathrm{ms} \pm 22.8 \mathrm{μs}\left({\color{gray}-0.753 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	10 entities	$$2.06 \mathrm{ms} \pm 9.08 \mathrm{μs}\left({\color{gray}-0.252 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	25 entities	$$2.69 \mathrm{ms} \pm 75.4 \mathrm{μs}\left({\color{lightgreen}-11.541 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	1 entities	$$1.84 \mathrm{ms} \pm 11.8 \mathrm{μs}\left({\color{gray}0.204 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	5 entities	$$1.88 \mathrm{ms} \pm 10.0 \mathrm{μs}\left({\color{gray}-0.139 \mathrm{\%}}\right) $$	Flame Graph

scaling_read_entity_linkless

Function	Value	Mean	Flame graphs
entity_by_id	1000 entities	$$2.74 \mathrm{ms} \pm 14.2 \mathrm{μs}\left({\color{lightgreen}-6.559 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	100 entities	$$2.04 \mathrm{ms} \pm 7.89 \mathrm{μs}\left({\color{gray}1.02 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	10 entities	$$1.85 \mathrm{ms} \pm 9.93 \mathrm{μs}\left({\color{gray}-4.463 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	10000 entities	$$9.43 \mathrm{ms} \pm 152 \mathrm{μs}\left({\color{gray}4.70 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	1 entities	$$1.88 \mathrm{ms} \pm 14.1 \mathrm{μs}\left({\color{gray}0.226 \mathrm{\%}}\right) $$	Flame Graph

representative_read_multiple_entities

Function	Value	Mean	Flame graphs
entity_by_property	depths: DT=2, PT=2, ET=2, E=2	$$60.4 \mathrm{ms} \pm 417 \mathrm{μs}\left({\color{gray}0.752 \mathrm{\%}}\right) $$	Flame Graph
entity_by_property	depths: DT=255, PT=255, ET=255, E=255	$$69.0 \mathrm{ms} \pm 409 \mathrm{μs}\left({\color{gray}-0.506 \mathrm{\%}}\right) $$	Flame Graph
entity_by_property	depths: DT=0, PT=0, ET=0, E=0	$$40.7 \mathrm{ms} \pm 415 \mathrm{μs}\left({\color{gray}-0.616 \mathrm{\%}}\right) $$	Flame Graph
entity_by_property	depths: DT=0, PT=0, ET=0, E=2	$$44.8 \mathrm{ms} \pm 438 \mathrm{μs}\left({\color{gray}-0.306 \mathrm{\%}}\right) $$	Flame Graph
entity_by_property	depths: DT=0, PT=2, ET=2, E=2	$$55.6 \mathrm{ms} \pm 392 \mathrm{μs}\left({\color{gray}-0.455 \mathrm{\%}}\right) $$	Flame Graph
entity_by_property	depths: DT=0, PT=0, ET=2, E=2	$$51.7 \mathrm{ms} \pm 418 \mathrm{μs}\left({\color{gray}-0.463 \mathrm{\%}}\right) $$	Flame Graph
link_by_source_by_property	depths: DT=2, PT=2, ET=2, E=2	$$99.4 \mathrm{ms} \pm 435 \mathrm{μs}\left({\color{gray}-0.636 \mathrm{\%}}\right) $$	Flame Graph
link_by_source_by_property	depths: DT=255, PT=255, ET=255, E=255	$$109 \mathrm{ms} \pm 744 \mathrm{μs}\left({\color{gray}0.205 \mathrm{\%}}\right) $$	Flame Graph
link_by_source_by_property	depths: DT=0, PT=0, ET=0, E=0	$$43.4 \mathrm{ms} \pm 217 \mathrm{μs}\left({\color{gray}0.430 \mathrm{\%}}\right) $$	Flame Graph
link_by_source_by_property	depths: DT=0, PT=0, ET=0, E=2	$$81.1 \mathrm{ms} \pm 582 \mathrm{μs}\left({\color{gray}-0.385 \mathrm{\%}}\right) $$	Flame Graph
link_by_source_by_property	depths: DT=0, PT=2, ET=2, E=2	$$95.0 \mathrm{ms} \pm 364 \mathrm{μs}\left({\color{gray}-0.934 \mathrm{\%}}\right) $$	Flame Graph
link_by_source_by_property	depths: DT=0, PT=0, ET=2, E=2	$$92.1 \mathrm{ms} \pm 502 \mathrm{μs}\left({\color{gray}0.946 \mathrm{\%}}\right) $$	Flame Graph

scaling_read_entity_complete_one_depth

Function	Value	Mean	Flame graphs
entity_by_id	50 entities	$$275 \mathrm{ms} \pm 1.64 \mathrm{ms}\left({\color{lightgreen}-30.833 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	10 entities	$$51.0 \mathrm{ms} \pm 242 \mathrm{μs}\left({\color{gray}-0.642 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	25 entities	$$73.1 \mathrm{ms} \pm 497 \mathrm{μs}\left({\color{gray}0.836 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	1 entities	$$19.8 \mathrm{ms} \pm 88.2 \mathrm{μs}\left({\color{gray}-0.039 \mathrm{\%}}\right) $$	Flame Graph
entity_by_id	5 entities	$$24.7 \mathrm{ms} \pm 126 \mathrm{μs}\left({\color{gray}-0.574 \mathrm{\%}}\right) $$	Flame Graph

[TimDiekmann]

Why is clean-up needed at all, why the session storage cannot be cleaned up after a session was terminated?

[indietyp]

this is for session termination, but we have no way to indicate to that a session has been terminated inline. so the net layer has a stream, with events, the only event (currently) is whenever a session is terminated. That is then relayed to this task which removes the session.

Another way this is often solved is through timing (e.g. 60 seconds of inactivity) but I wanted to avoid that approach.