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Ensure BeforeBestBlockBy voting rule accounts for base#9920
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ordian
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Oct 2, 2021
* master: (67 commits) Downstream `node-template` pull (#9915) Implement core::fmt::Debug for BoundedVec (#9914) Quickly skip invalid transactions during block authorship. (#9789) Add SS58 prefix for Automata (#9805) Clean up sc-peerset (#9806) Test each benchmark case in own #[test] (#9860) Add build with docker section to README (#9792) Simple Trait to Inspect Metadata (#9893) Pallet Assets: Create new asset classes from genesis config (#9742) doc: subkey usage (#9905) Silence alert about large-statement-fetcher (#9882) Fix democracy on-initialize weight (#9890) Fix basic authorship flaky test (#9906) contracts: Add event field names (#9896) subkey readme update on install (#9900) add feature wasmtime-jitdump (#9871) Return `target_hash` for finality_target instead of an Option (#9867) Update wasmtime to 0.29.0 (#9552) Less sleeps (#9848) remove unidiomatic (#9895) ...
andresilva
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Oct 3, 2021
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Good catch and thanks for the fix!
ordian
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Oct 5, 2021
* master: (125 commits) Update multiple dependencies (#9936) Speed up timestamp generation when logging (#9933) First word should be Substrate not Polkadot (#9935) Improved file not found error message (#9931) don't read events in elections anymore. (#9898) Remove incorrect sanity check (#9924) Require crypto scheme for `insert-key` (#9909) chore: refresh of the substrate_builder image (#9808) Introduce block authorship soft deadline (#9663) Rework Transaction Priority calculation (#9834) Do not propagate host RUSTFLAGS when checking for WASM toolchain (#9926) Small quoting comment fix (#9927) add clippy to CI (#9694) Ensure BeforeBestBlockBy voting rule accounts for base (#9920) rm `.maintain` lock (#9919) Downstream `node-template` pull (#9915) Implement core::fmt::Debug for BoundedVec (#9914) Quickly skip invalid transactions during block authorship. (#9789) Add SS58 prefix for Automata (#9805) Clean up sc-peerset (#9806) ...
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The changeset here is just to modify
BeforeBestBlockByto check whether voting N blocks behind is even possible, and if not, it votes on the base.This is fixing a bug that manifested on the Rococo network after activating Polkadot's custom fork-choice rule, which can prioritize shorter chains over longer ones.
A diagram for illustration:
In this scenario, finality for B is racing with the production of B1'. If B is finalized before B1' is produced, nodes with B1' as their best chain will attempt to vote before block B and this is ignored by the voting rule machinery and leads to voting to finalize B1'. Then, if B1' is finalized before a block B2' is built on top of it, the cycle repeats, and can repeat indefinitely. This undermines the intention of the voting rule, hence the fix.