Move poll & quorum functionality into ProgressSet #121
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hicqu
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Sep 29, 2018
hicqu
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hicqu
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@huachaohuang sorry, wrong person. ^^ |
Hoverbear
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@overvenus @hicqu please take a look again. |
hicqu
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Nov 8, 2018
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LGTM. 👍 Please take look at |
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@hicqu @overvenus Please consider the responses to your feedback, I have suggested new names. :) |
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@overvenus thanks for the great input. :) Reflected your suggestion. |
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Nov 21, 2018
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LGTM. |
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121: Move poll & quorum functionality into ProgressSet r=Hoverbear a=Hoverbear Based off #119. **You are seeing that change set as well here, so go review that, then this after merging it! :)** Migrate poll and quorum related functionality inside `ProgressSet`. These functions operated on the `ProgressSet` anyways, they were just scoped to the `Raft`. # Rationale With the introduction of Joint Consensus, the idea of a Quorum is no longer always a single value. (If the cluster is in a joint state it actually has two quorums. The old configuration and the new one.) In the interest of isolating responsibility and dulling sharp edges, this PR migrates code the following functionality: * `check_quorum_active`: Migrated, it was doing a mutable fold on the peers and resetting their recent active, then returning if there was enough for quorum. The `ProgressSet` can do this itself, and it means we can avoid having to return some enum of either `(quorum)` or `(new_quorum, old_quorum)`. The `Raft` module need not care. * `poll`: Was split into a mutating vote-setter function, and a check function (non mutating). The check function returns a semantically meaningful enum now. This was a good idea since `poll(vote) >= quorum`, while still valid, may be comparing tuples or values. Internalizing this logic and instead returning a semantic value helps with understanding. * `minimum_committed_index`: Since in a joint consensus state we need to check the minimum committed index of both old and new, we can internalize this check and just return a bool. # Benefits This PR essentially amounts to API cleaning. It doesn't change any behavior, but it's a change we should do to make future work easier. # Future Work When Joint Consensus (#101 ) lands it will change these new functions to be joint-aware and correctly return values regardless of the configuration state. Co-authored-by: Hoverbear <andrew@hoverbear.org> Co-authored-by: Hoverbear <operator@hoverbear.org> Co-authored-by: A. Hobden <andrew@hoverbear.org> Co-authored-by: A. Hobden <operator@hoverbear.org> Co-authored-by: qupeng <onlyqupeng@gmail.com>
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Based off #119. You are seeing that change set as well here, so go review that, then this after merging it! :)
Migrate poll and quorum related functionality inside
ProgressSet.These functions operated on the
ProgressSetanyways, they were just scoped to theRaft.Rationale
With the introduction of Joint Consensus, the idea of a Quorum is no longer always a single value. (If the cluster is in a joint state it actually has two quorums. The old configuration and the new one.)
In the interest of isolating responsibility and dulling sharp edges, this PR migrates code the following functionality:
check_quorum_active: Migrated, it was doing a mutable fold on the peers and resetting their recent active, then returning if there was enough for quorum. TheProgressSetcan do this itself, and it means we can avoid having to return some enum of either(quorum)or(new_quorum, old_quorum). TheRaftmodule need not care.poll: Was split into a mutating vote-setter function, and a check function (non mutating). The check function returns a semantically meaningful enum now. This was a good idea sincepoll(vote) >= quorum, while still valid, may be comparing tuples or values. Internalizing this logic and instead returning a semantic value helps with understanding.minimum_committed_index: Since in a joint consensus state we need to check the minimum committed index of both old and new, we can internalize this check and just return a bool.Benefits
This PR essentially amounts to API cleaning. It doesn't change any behavior, but it's a change we should do to make future work easier.
Future Work
When Joint Consensus (#101 ) lands it will change these new functions to be joint-aware and correctly return values regardless of the configuration state.