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// Copyright 2019 The etcd Authors
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// See the License for the specific language governing permissions and
// limitations under the License.
package quorum
// JointConfig is a configuration of two groups of (possibly overlapping)
// majority configurations. Decisions require the support of both majorities.
type JointConfig [2]MajorityConfig
func (c JointConfig) String() string {
if len(c[1]) > 0 {
return c[0].String() + "&&" + c[1].String()
return c[0].String()
// IDs returns a newly initialized map representing the set of voters present
// in the joint configuration.
func (c JointConfig) IDs() map[uint64]struct{} {
m := map[uint64]struct{}{}
for _, cc := range c {
for id := range cc {
m[id] = struct{}{}
return m
// Describe returns a (multi-line) representation of the commit indexes for the
// given lookuper.
func (c JointConfig) Describe(l AckedIndexer) string {
return MajorityConfig(c.IDs()).Describe(l)
// CommittedIndex returns the largest committed index for the given joint
// quorum. An index is jointly committed if it is committed in both constituent
// majorities.
func (c JointConfig) CommittedIndex(l AckedIndexer) Index {
idx0 := c[0].CommittedIndex(l)
idx1 := c[1].CommittedIndex(l)
if idx0 < idx1 {
return idx0
return idx1
// VoteResult takes a mapping of voters to yes/no (true/false) votes and returns
// a result indicating whether the vote is pending, lost, or won. A joint quorum
// requires both majority quorums to vote in favor.
func (c JointConfig) VoteResult(votes map[uint64]bool) VoteResult {
r1 := c[0].VoteResult(votes)
r2 := c[1].VoteResult(votes)
if r1 == r2 {
// If they agree, return the agreed state.
return r1
if r1 == VoteLost || r2 == VoteLost {
// If either config has lost, loss is the only possible outcome.
return VoteLost
// One side won, the other one is pending, so the whole outcome is.
return VotePending