Add probing service#815
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Hi @randomlogin, thanks for the work on this! I've reviewed the first two commits:
I've left a bunch of inline comments addressing configuration and public API, commit hygiene, testing infrastructure, and test flakiness.
In summary:
- A couple of items are exposed publicly that seem like they should be scoped to probing or gated for tests only (see
scoring_fee_paramsinConfigandscorer_channel_liquidityonNode). - The probing tests duplicate existing test helpers (
setup_node,MockLogFacadeLogger). Reusing and extending what's already intests/common/would reduce duplication and keep the test file focused on the tests themselves. test_probe_budget_blocks_when_node_offlinehas a race condition where the prober dispatches probes before the baseline capacity is measured, causing the assertion between the baseline and stuck capacities to fail. Details in the inline comment.- A few nits about commit hygiene, import structure, and suggestions for renaming stuff.
Also needs to be rebased.
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@enigbe, thanks for a review, the updates are incoming soon. |
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Thanks for taking this on and excuse the delay here!
Did a first review pass and this already looks great! Here are some relatively minor comments, mostly concerning the API design.
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Seems tests are failing right now:
thread 'exhausted_probe_budget_blocks_new_probes' (167312) panicked at tests/probing_tests.rs:381:5:
no probe dispatched within 15 s
failures:
exhausted_probe_budget_blocks_new_probes
probe_budget_increments_and_decrements
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It seems your git commit history got mangled and this PR now touches almost every file. Please clean it up and rebase on current main. Please refer to https://cbea.ms/git-commit/ for some guidance on how to structure commits and how to write good descriptions.
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This still need a rebase.
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Now it should be fine. Previously I've accidentally absorbed changes from the main without a proper merge. Should I squash my commits (especially with the abundance of empty CI re-trigger commits I made)? Also regarding the commit messages, I'll to be more accurate (and follow case styling). Please, don't hesitate to tell me once again if it occurs. Also ideally the commits should be more granular, right? |
Yes, fixed in #891.
Yes, please generally restructure your commit history so it has a few logical 'feature' commit and preferably only add fixups right after them, so they can be squashed in once reviewed. Usually you'd prefix their commit description with
Yes, that would be great. Preferably code introduced in earlier commit doesn't get changed again in later commits, and all revisions should build test, and format independently. |
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Introduce a background probing service that periodically sends payment probes to discover liquidity along Lightning routes. Probes update the local scorer with channel liquidity information, improving pathfinding for subsequent real payments. The service supports three strategies: - HighDegree: probes nodes with the most channels in the network graph - Random: walks random paths from the local node - Custom: user-supplied strategy via the `ProbingStrategy` trait A dedicated `ProbingConfigBuilder` exposes amount bounds, locked-msat caps, probing intervals, and per-node cooldowns, with sensible defaults. The service runs as a cancellable background task driven by the existing `Runtime`, and budget accounting tracks both in-flight and locked amounts to bound outbound liquidity exposure. UniFFI bindings expose the probing service to the Swift, Kotlin, and Python language bindings. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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The exhausted_probe_budget_blocks_new_probes test and the linting CI job are failing unfortunately. Regarding the latter, note that we recently banned unwrap project-wide in non-test code, so you'll need to use except everywhere, eg., except("lock") when acquiring locks.
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Add integration tests that verify the probing service fires probes on the configured interval and respects the locked-msat budget cap. Shared helpers in tests/common are extended with probing-aware setup. Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>
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Changed the exhaust test to be statistical (locked amount never exceeds the cap) instead of trying to turn intermediary routing node offline when it hasn't yet forwarded the probe htlc.
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Removed usage of unwrap(), reworked the exhaust test not to rely on a node stopping race condition. |
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Added a probing service which is used to send probes to estimate channels' capacities.
Related issue: #765.
Probing is intended to be used in two ways:
For probing a new abstraction
Proberis defined and is (optionally) created during node building.Prober periodically sends probes to feed the data to the scorer.
Prober sends probes using a ProbingStrategy.
ProbingStrategy trait has only one method:
fn next_probe(&self) -> Option<Probe>; every tick it generates a probe, whereProberepresents how to send a probe.To accommodate two different ways the probing is used, we either construct a probing route manually (
Probe::PrebuiltRoute) or rely on the router/scorer (Probe::Destination).Prober tracks how much liquidity is locked in-flight in probes, prevents the new probes from firing if the cap is reached.
There are two probing strategies implemented:
Random probing strategy, it picks a random route from the current node, the route is probed via
send_probe, thus ignores scoring parameters (what hops to pick), it also ignoresliquidity_limit_multiplierwhich prohibits taking a hop if its capacity is too small. It is a true random route.High degree probing strategy, it examines the graph and finds the nodes with the biggest number of (public) channels and probes routes to them using
send_spontaneous_preflight_probeswhich uses the current router/scorer.The former is meant to be used on payment nodes, while the latter on probing nodes. For the HighDegreeStrategy to work it is recommended to set
probing_diversity_penalty_msatto some nonzero value to prevent routes reuse, however it may fail to find any available routes.There are three tests added:
Example output (runs for ~1 minute, needs
--nocaptureflag):For performance testing I had to expose the scoring data (
scorer_channel_liquidity).Also exposed
scoring_fee_params: ProbabilisticScoringFeeParameterstoConfig.TODOs: