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grandpa: pass the actual best block to voting rules #12477
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andresilva
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ordian
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skunert
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davxy
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LGTM
Just to elaborate (correct me if I misunderstood something)
- The
SelectChain::finality_targetimplementation in Polkadot (SelectRelayChain) restricts the returned hash to only chains which are fully approved and which contains no disputes. - If we already lowered the bar and we don't use the "real best", then the filters used later in
voting_rule.restrict_vote()can unnecessarily lower the end target (e.g. because the "3/4" or the "before best by" rules which takes as the reference upper bound thebest_headerthat is passed in)
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@davxy Your understanding is accurate! 👍 |
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Hey, is anyone still working on this? Due to the inactivity this issue has been automatically marked as stale. It will be closed if no further activity occurs. Thank you for your contributions. |
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Not stale. @andresilva can we merge this or you found something you like to fix? |
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melekes
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Dec 26, 2022
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bot merge |
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ltfschoen
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* grandpa: pass the actual best block to voting rules * grandpa: add test for checking best header is passed to voting rule
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* grandpa: pass the actual best block to voting rules * grandpa: add test for checking best header is passed to voting rule
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GRANDPA allows plugging custom voting rules that will restrict the round votes according to some arbitrary logic. For these voting rules to make their decision we pass along the base block (i.e. the round base, we will finalize something that must be a descendant of this block), the best block and the target block (i.e. the block we will be aiming to finalize this round before potentially restricting it further with voting rules). As an example, one of the voting rules is that the block we target to finalize must always be
Nblocks behind the best block.The block that we were passing along to the voting rule as the best block was actually the target block as returned by
SelectChain::finality_target(without limiting it due to authority set changes). This made it so that, depending on the voting rules, we could unnecessarily restrict votes (as was the case with Polkadot). This PR changes this logic to pass the actual best block as computed bySelectChain::best_chain.cc @ordian