Re-introduces the second rebalancing track (Track B, "xrebalance": the
circular askrene min-cost-flow rebalancer) into the shared selection and
layer infrastructure, so it can coexist with the classic track in one
binary and be chosen at runtime.
- Boss::RebalanceMode gains the xrebalance value (+ to_string /
from_string arms and the doc bullet), selectable via
clboss-rebalance-mode alongside classic and off.
- Boss::Mod::AskreneLayer gains xrebalance_layer_name
("clboss-xrebalance"), the persistent askrene layer the xrebalance
code paths accumulate probe knowledge into. Kept distinct from the
"clboss" layer so the two tracks' learning does not commingle while
both run side by side.
- clboss-rebalance-mode help text now lists xrebalance.
This is only the seam: nothing drives xrebalance yet. The XMoveFunds
primitive and the XRebalancer driver land in following commits. The
classic rebalancers already gate on mode == classic, so selecting
xrebalance simply quiesces them (like off) until the driver arrives.
setconfig was acknowledged with unconditional success after
broadcasting Msg::Option, while owning modules reject bad values by
log-and-keep. lightningd persists a setconfig value (configvar_save)
only on a success response, so the blanket ack recorded values clboss
never applied: listconfigs and config.setconfig diverged from the
running configuration, and a non-numeric value persisted for an
int-typed option fails lightningd's own option parse on the next
start -- lightningd refuses to boot.
Add a rejection back-channel to Msg::Option: SetConfigHandler
allocates a shared reject_reason (null on init-time raises, so
aggregate initialization at existing sites is unaffected), the owning
subscriber reports rejection via the new Msg::Option::reject() helper
(a no-op at init time, where quietly keeping the default is right),
and SetConfigHandler -- whose bus.raise() returns only after all
subscribers ran -- fails the command with invalid-params when a
reason was set. All dynamic-option owners in this tree report their
rejections: RebalanceModeManager (unrecognized mode), FundsMover's
three numeric handlers, and AskreneUpdates' shared age/retain
handler.
Introduces a single source of truth for which rebalancing track is
active. Boss::Mod::RebalanceModeManager owns the mode in memory (no
sqlite, so a restart reverts to the configured default, giving a
known-good baseline on every boot) and registers clboss-rebalance-mode
as a dynamic option: the config file sets the startup default and
`setconfig clboss-rebalance-mode <mode>` switches it at runtime without
a restart. It answers RequestRebalanceMode queries and reports the mode
under clboss-status.
Modes are "classic" (run the rebalancer) and "off" (a real quiesce,
also the supported way to disable rebalancing entirely). This is the
seam that later lets a second rebalancing track coexist and be toggled
without a restart.
The classic-track rebalancers self-gate on the mode at their existing
decision points, modeled on RebalanceUnmanager: EarningsRebalancer gates
its trigger, InitialRebalancer gates its run, and JitRebalancer gates
the top of htlc_accepted so that in off mode it does not defer the HTLC
and adds no forwarding latency. A header-only Boss::ModG::
RebalanceModeProxy provides get_mode for the gate sites. off composes
with the existing per-peer unmanage balance tag: off wins globally,
otherwise the per-peer tag still excludes specific peers.
The three rebalancers' unit tests now install a RebalanceModeManager on
the test bus so the self-gate query is answered (default classic, so
they behave as before). Without a responder the RequestRebalanceMode
ReqResp is never satisfied and leaks, which the valgrind-checked tests
flag as a failure.
New files: Boss/RebalanceMode.hpp, Boss/Msg/RequestRebalanceMode.hpp,
Boss/Msg/ResponseRebalanceMode.hpp, Boss/ModG/RebalanceModeProxy.hpp,
Boss/Mod/RebalanceModeManager.{hpp,cpp}.
