chore(config): retire the two zenoh 1.9 removed routing keys

[YuanYuYuan]

Summary

zenoh 1.9 removed two config keys that hiroz still set. zenoh-config carries a deprecation wrapper for each, and warns on both.

key	where hiroz set it	value
routing.router.peers_failover_brokering	crates/hiroz/src/config.rs, router overrides	false
routing.router.peers_failover_brokering	crates/rmw-zenoh-rs/config/…SESSION_CONFIG.json5	true
routing.peer.mode	the same JSON5 file	"peer_to_peer"

The two settings of the first key disagreed with each other. None of the three does anything. The runtime says so on every start of anything that sets it:

WARN zenoh_config: `routing.router.peers_failover_brokering` is deprecated and
has no effect; please remove it from your configuration

This change removes all three, and adds a test that pins their absence. With routing.peer gone the JSON5 file's routing block held nothing live, so that goes too.

The second one is also in the wrong file. It is a session config, and the key governs what a router does when forwarding between two peers attached to it. A session is not a router, so it would have had no effect there even on a runtime that honoured it.

What the key used to do, measured

The flag was real. It is still live on rmw_zenoh_cpp jazzy 0.2.9, where the same measurement runs both ways with one word changed in the router config:

peers_failover_brokering	published	cross-host heard
false (its shipped value)	75	0
true	75	75

The listener's own log gives the mechanism:

false: WARN ... Unable to connect to any locator of scouted peer c76ee898...: [tcp/[::1]:34357]
true:  [INFO] [lb1]: I heard: [Hello World: 1]

That the false cell scouted the talker proves both nodes shared a router. Gossip reached across; only the data path did not.

So zenoh 1.9 removed a capability, not a dead option. Know that before deleting the key. It also deserves a line in whatever documents the upgrade.

Why removing it costs nothing here

the capability only applies to two peers sharing one router	a router does not relay between peers attached to it without this flag
hiroz defaults to a router per host	connect/endpoints is tcp/localhost:7447, so every node reaches a router on its own machine
in that topology the key has no role	traffic crosses router to router, which this flag never governed
both projects already shipped it off	hiroz false, rmw_zenoh_cpp false

Measured across topologies, hiroz delivers cross-host either way:

router layout	cross-host heard / published	cross-host peer links
router per host (the default)	149 / 150	0
one shared router	0 / 150	0

The shared-router row is a separate problem, and this change does not address it. This records it rather than fixing it, because a deployment reaches that row only by overriding the shipped connect endpoint.

What fails without this

Nothing fails. The keys are inert; that is the point.

	today	with this change
the_shipped_overrides_name_no_removed_key	fails: the router overrides name peers_failover_brokering	passes
the_vendored_config_files_set_no_removed_key	fails: the session JSON5 sets both keys	passes
router startup	warns about a deprecated key	silent

Both assertions run in every direction: green as committed, then one red probe per key per surface — four in all, each returning rc=101. Each arm fires only on its own surface, so they are two independent checks rather than one written twice. Both also assert their input is non-empty, so neither can pass vacuously.

The two surfaces need different needles for the same key. An override spells it as a path, routing/peer/mode; a JSON5 file spells it as nested blocks with the value on the leaf. An earlier version of this test used one token for both and would have missed the file side in silence.

An earlier revision of that test asserted against format!("{config:?}"). That renders zenoh's whole config tree, defaults included. It therefore could not tell an override from a field that merely exists, and it failed on a clean tree. It now inspects router_overrides() and session_overrides() — what hiroz sets.

Test results

check	result
cargo test -p hiroz on this branch	55 passed, 7 failed
cargo test -p hiroz on main	55 passed, 7 failed
failures unique to this branch	none
cargo clippy -p hiroz --all-targets -- -D warnings	clean
cargo fmt --check	clean

The 7 are pre-existing doctest compile failures in action/client.rs and action/server.rs (ZActionClient, ZActionClientBuilder, GoalHandle, ZActionServerBuilder). Confirmed against main rather than assumed.

Breaking changes

None. Both keys are inert on zenoh 1.9, so no behaviour changes at any setting.

Not verified

• hiroz on zenoh 1.8. Every "the flag was live" number above comes from rmw_zenoh_cpp jazzy 0.2.9, which is a different stack. A true before-and-after needs hiroz pinned to zenoh = "1.8".
• The zenoh version behind that C++ build. libzenohc.so carries no symbols, and three probe strategies recovered no version string.
• Whether any deployment relied on this flag. Both projects shipped it off, but a user config could have set it.

[Copilot]

Pull request overview

Updates peer networking defaults so hiroz nodes can communicate across hosts.

Changes:

• Binds peer sessions to all interfaces.
• Removes a deprecated router override.
• Adds default-session connectivity and configuration tests.

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated 1 comment.

File	Description
crates/hiroz/src/config.rs	Updates session and router defaults.
crates/hiroz/tests/two_session_default_config.rs	Tests independent default sessions and reachable listeners.

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[Copilot]

Pull request overview

Copilot reviewed 3 out of 3 changed files in this pull request and generated no new comments.