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| 1 | +use crate::error::ChangeMembershipError; |
| 2 | +use crate::error::InProgress; |
| 3 | +use crate::ChangeMembers; |
| 4 | +use crate::Membership; |
| 5 | +use crate::MembershipState; |
| 6 | +use crate::Node; |
| 7 | +use crate::NodeId; |
| 8 | + |
| 9 | +pub(crate) struct ChangeHandler<'m, NID, N> |
| 10 | +where |
| 11 | + NID: NodeId, |
| 12 | + N: Node, |
| 13 | +{ |
| 14 | + pub(crate) state: &'m MembershipState<NID, N>, |
| 15 | +} |
| 16 | + |
| 17 | +impl<'m, NID, N> ChangeHandler<'m, NID, N> |
| 18 | +where |
| 19 | + NID: NodeId, |
| 20 | + N: Node, |
| 21 | +{ |
| 22 | + /// Builds a new membership configuration by applying changes to the current configuration. |
| 23 | + /// |
| 24 | + /// * `changes`: The changes to apply to the current membership configuration. |
| 25 | + /// * `retain` specifies whether to retain the removed voters as a learners, i.e., nodes that |
| 26 | + /// continue to receive log replication from the leader. |
| 27 | + /// |
| 28 | + /// A Result containing the new membership configuration if the operation succeeds, or a |
| 29 | + /// `ChangeMembershipError` if an error occurs. |
| 30 | + /// |
| 31 | + /// This function ensures that the cluster will have at least one voter in the new membership |
| 32 | + /// configuration. |
| 33 | + pub(crate) fn apply( |
| 34 | + &self, |
| 35 | + change: ChangeMembers<NID, N>, |
| 36 | + retain: bool, |
| 37 | + ) -> Result<Membership<NID, N>, ChangeMembershipError<NID>> { |
| 38 | + self.ensure_committed()?; |
| 39 | + |
| 40 | + let new_membership = self.state.effective().membership.clone().change(change, retain)?; |
| 41 | + Ok(new_membership) |
| 42 | + } |
| 43 | + |
| 44 | + /// Ensures that the latest membership has been committed. |
| 45 | + /// |
| 46 | + /// Returns Ok if the last membership is committed, or an InProgress error |
| 47 | + /// otherwise, to indicate a change-membership request should be rejected. |
| 48 | + pub(crate) fn ensure_committed(&self) -> Result<(), InProgress<NID>> { |
| 49 | + let effective = self.state.effective(); |
| 50 | + let committed = self.state.committed(); |
| 51 | + |
| 52 | + if effective.log_id == committed.log_id { |
| 53 | + // Ok: last membership(effective) is committed |
| 54 | + Ok(()) |
| 55 | + } else { |
| 56 | + Err(InProgress { |
| 57 | + committed: committed.log_id, |
| 58 | + membership_log_id: effective.log_id, |
| 59 | + }) |
| 60 | + } |
| 61 | + } |
| 62 | +} |
| 63 | + |
| 64 | +#[cfg(test)] |
| 65 | +mod tests { |
| 66 | + use std::sync::Arc; |
| 67 | + |
| 68 | + use maplit::btreemap; |
| 69 | + use maplit::btreeset; |
| 70 | + |
| 71 | + use crate::error::ChangeMembershipError; |
| 72 | + use crate::error::EmptyMembership; |
| 73 | + use crate::error::InProgress; |
| 74 | + use crate::error::LearnerNotFound; |
| 75 | + use crate::testing::log_id; |
| 76 | + use crate::ChangeMembers; |
| 77 | + use crate::EffectiveMembership; |
| 78 | + use crate::Membership; |
| 79 | + use crate::MembershipState; |
| 80 | + |
| 81 | + /// Create an Arc<EffectiveMembership> |
| 82 | + fn effmem(term: u64, index: u64, m: Membership<u64, ()>) -> Arc<EffectiveMembership<u64, ()>> { |
| 83 | + let lid = Some(log_id(term, index)); |
| 84 | + Arc::new(EffectiveMembership::new(lid, m)) |
| 85 | + } |
| 86 | + |
| 87 | + fn m1() -> Membership<u64, ()> { |
| 88 | + Membership::new(vec![btreeset! {1}], None) |
| 89 | + } |
| 90 | + |
| 91 | + fn m12() -> Membership<u64, ()> { |
| 92 | + Membership::new(vec![btreeset! {1,2}], None) |
| 93 | + } |
| 94 | + |
| 95 | + fn m123_345() -> Membership<u64, ()> { |
| 96 | + Membership::new(vec![btreeset! {1,2,3}, btreeset! {3,4,5}], None) |
| 97 | + } |
| 98 | + |
| 99 | + #[test] |
| 100 | + fn test_apply_not_committed() -> anyhow::Result<()> { |
| 101 | + let new = || MembershipState::new(effmem(2, 2, m1()), effmem(3, 4, m123_345())); |
| 102 | + let res = new().change_handler().apply(ChangeMembers::AddVoter(btreeset! {1}), false); |
| 103 | + |
| 104 | + assert_eq!( |
| 105 | + Err(ChangeMembershipError::InProgress(InProgress { |
| 106 | + committed: Some(log_id(2, 2)), |
| 107 | + membership_log_id: Some(log_id(3, 4)) |
| 108 | + })), |
| 109 | + res |
| 110 | + ); |
| 111 | + |
| 112 | + Ok(()) |
| 113 | + } |
| 114 | + |
| 115 | + #[test] |
| 116 | + fn test_apply_empty_voters() -> anyhow::Result<()> { |
| 117 | + let new = || MembershipState::new(effmem(3, 4, m1()), effmem(3, 4, m1())); |
| 118 | + let res = new().change_handler().apply(ChangeMembers::RemoveVoter(btreeset! {1}), false); |
| 119 | + |
| 120 | + assert_eq!(Err(ChangeMembershipError::EmptyMembership(EmptyMembership {})), res); |
| 121 | + |
| 122 | + Ok(()) |
| 123 | + } |
| 124 | + |
| 125 | + #[test] |
| 126 | + fn test_apply_learner_not_found() -> anyhow::Result<()> { |
| 127 | + let new = || MembershipState::new(effmem(3, 4, m1()), effmem(3, 4, m1())); |
| 128 | + let res = new().change_handler().apply(ChangeMembers::AddVoter(btreeset! {2}), false); |
| 129 | + |
| 130 | + assert_eq!( |
| 131 | + Err(ChangeMembershipError::LearnerNotFound(LearnerNotFound { node_id: 2 })), |
| 132 | + res |
| 133 | + ); |
| 134 | + |
| 135 | + Ok(()) |
| 136 | + } |
| 137 | + |
| 138 | + #[test] |
| 139 | + fn test_apply_retain_learner() -> anyhow::Result<()> { |
| 140 | + let new = || MembershipState::new(effmem(3, 4, m12()), effmem(3, 4, m123_345())); |
| 141 | + |
| 142 | + // Do not leave removed voters as learner |
| 143 | + let res = new().change_handler().apply(ChangeMembers::RemoveVoter(btreeset! {1,2}), false); |
| 144 | + assert_eq!( |
| 145 | + Ok(Membership::new(vec![btreeset! {3,4,5}], btreemap! {3=>(),4=>(),5=>()})), |
| 146 | + res |
| 147 | + ); |
| 148 | + |
| 149 | + // Leave removed voters as learner |
| 150 | + let res = new().change_handler().apply(ChangeMembers::RemoveVoter(btreeset! {1,2}), true); |
| 151 | + assert_eq!( |
| 152 | + Ok(Membership::new( |
| 153 | + vec![btreeset! {3,4,5}], |
| 154 | + btreemap! {1=>(),2=>(),3=>(),4=>(),5=>()} |
| 155 | + )), |
| 156 | + res |
| 157 | + ); |
| 158 | + |
| 159 | + Ok(()) |
| 160 | + } |
| 161 | +} |
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