client/authority-discovery: Introduce AuthorityDiscoveryService

[mxinden]

Add a basic AuthorityDiscoveryService implementation which enables
callers to get the addresses for a given AuthorityId and the AuthorityId
for a given PeerId from the local cache.

impl Service {
        /// Get the addresses for the given [`AuthorityId`] from the local address cache.
	pub async fn get_addresses_by_authority_id(&mut self, authority: AuthorityId) -> Option<Vec<Multiaddr>> {
		// ...
	}

	/// Get the [`AuthorityId`] for the given [`PeerId`] from the local address cache.
	pub async fn get_authority_id_by_peer_id(&mut self, peer_id: PeerId) -> Option<AuthorityId> {
                // ...
	}
}

To achieve the above this pull request also

• Restructures the crate into Service and Worker (e9a12e8).

• Updates the peerset priority group on an interval instead of on each DHT value found (ad1a711).

---

Fixes #6595.

polkadot companion: paritytech/polkadot#1563

[mxinden]

While still missing a simple Polkadot companion, this pull request is ready for a first review @tomaka @rphmeier.

e9a12e8 moves around most of the code resulting in a large overall diff (+1,732 −1,402). You can either look at the whole change at once, or, commit by commit ignoring most of e9a12e8.

[tomaka]

Weren't we also supposed to remove the automatic update of the peerset?
This can be done later.

[tomaka]

Could you document that the addresses are always of the form .../p2p/...?
And also document that None means that the authority isn't in the cache.

[tomaka]

Same remark: None means "not in cache".

[mxinden]

Weren't we also supposed to remove the automatic update of the peerset?

I would prefer to keep it in place until upper layer components are capable of handling it themselves.

Could you document that the addresses are always of the form .../p2p/...?

Done in 30613ce.

And also document that None means that the authority isn't in the cache.

Documented in 05664d7. Right now, the case of connection failure between Service and Worker is also modeled as None. Let me know @tomaka in case you would prefer that to be a separate Result wrapped around the Option<Vec<Multiaddr>>.

[tomaka]

Documented in 05664d7. Right now, the case of connection failure between Service and Worker is also modeled as None. Let me know @tomaka in case you would prefer that to be a separate Result wrapped around the Option<Vec>.

Since None means "not-in-cache/unknown", then it covers the situation where the worker is down.

[tomaka]

I think this is ready for merge, just waiting to see if @rphmeier wants to review or not.

[rphmeier]

@tomaka If the APIs match what is in the description and the code seems OK to you, it's fine by me, I don't need to review

[mxinden]

Thanks for the reviews!

@ordian would you mind taking another look?

[ordian]

Looks good!

[tomaka]

bot merge

[ghost]

Waiting for commit status.

[ghost]

Checks failed; merge aborted.

[ordian]

bot merge

[ghost]

Trying merge.