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NRG (2.11): Vote request cancels catchup, new leader could have rejected subsequent catchup messages #6072

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merged 1 commit into from
Nov 4, 2024
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NRG (2.11): Vote request cancels catchup, new leader could have rejected subsequent catchup messages #6072

merged 1 commit into from
Nov 4, 2024

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MauriceVanVeen
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Antithesis triggered a case where:

  • a follower (S0) is behind and triggers catchup from the leader (S2)
  • another follower (S1) triggers leader election
  • the follower (S0) allows follower (S1) to become leader
  • the leader (S2) sends a new message, which new leader (S1) rejects because it's on a higher term
  • the follower (S0) now receives above message that new leader (S1) rejected, providing previous leader (S2) with quorum
  • the new leader (S1) rejected that message, so previous leader (S2) has now desynced since it applied the message

This is solved by canceling catchup once a leader election happens for a higher term. The new leader will then resume our catchup once it's elected.

Signed-off-by: Maurice van Veen [email protected]

@MauriceVanVeen MauriceVanVeen changed the title NRG: Vote request cancels catchup, new leader could have rejected subsequent catchup messages NRG (2.11): Vote request cancels catchup, new leader could have rejected subsequent catchup messages Nov 4, 2024
neilalexander
neilalexander reviewed Nov 4, 2024
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@MauriceVanVeen
NRG: Vote request cancels catchup, new leader could have rejected sub…
0f7cf3d 
…sequent catchup messages

Signed-off-by: Maurice van Veen <[email protected]>
@MauriceVanVeen MauriceVanVeen force-pushed the maurice/desync-with-vote-req-during-catchup branch from 552658b to 0f7cf3d Compare November 4, 2024 13:35
neilalexander
neilalexander approved these changes Nov 4, 2024
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LGTM

@neilalexander neilalexander marked this pull request as ready for review November 4, 2024 15:14
@neilalexander neilalexander requested a review from a team as a code owner November 4, 2024 15:14
derekcollison
derekcollison approved these changes Nov 4, 2024
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LGTM

@derekcollison derekcollison merged commit 633bb94 into main Nov 4, 2024
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@derekcollison derekcollison deleted the maurice/desync-with-vote-req-during-catchup branch November 4, 2024 16:21
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@neilalexander neilalexander neilalexander approved these changes

@derekcollison derekcollison derekcollison approved these changes

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@MauriceVanVeen @derekcollison @neilalexander