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etcdserver: fix quorum calculation when promoting a learner member

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When promoting a learner member we should not count already a voting
member, but take only into account the number of existing voting
members and their current status (started, unstarted) when taking the
decision whether a learner member can be promoted.

Before this change, it was impossible to grow from a quorum N to a N+1
through promoting a learning member.

Fixes: #11633
This commit is contained in:
Rafael Fernández López 2020-02-19 17:39:01 +01:00 committed by jingyih
parent cdb2dc11b8
commit 257319fb18
2 changed files with 89 additions and 2 deletions
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4
etcdserver/api/membership/cluster.go
View File

@ -657,8 +657,8 @@ func (c *RaftCluster) IsReadyToRemoveVotingMember(id uint64) bool {
}
func (c *RaftCluster) IsReadyToPromoteMember(id uint64) bool {
nmembers := 1
nstarted := 0
nmembers := 1 // We count the learner to be promoted for the future quorum
nstarted := 1 // and we also count it as started.
for _, member := range c.VotingMembers() {
if member.IsStarted() {

87
etcdserver/api/membership/cluster_test.go
View File

@ -859,3 +859,90 @@ func TestIsReadyToRemoveVotingMember(t *testing.T) {
}
}
}
func TestIsReadyToPromoteMember(t *testing.T) {
tests := []struct {
members []*Member
promoteID uint64
want bool
}{
{
// 1/1 members ready, should succeed (quorum = 1, new quorum = 2)
[]*Member{
newTestMember(1, nil, "1", nil),
newTestMemberAsLearner(2, nil, "2", nil),
},
2,
true,
},
{
// 0/1 members ready, should fail (quorum = 1)
[]*Member{
newTestMember(1, nil, "", nil),
newTestMemberAsLearner(2, nil, "2", nil),
},
2,
false,
},
{
// 2/2 members ready, should succeed (quorum = 2)
[]*Member{
newTestMember(1, nil, "1", nil),
newTestMember(2, nil, "2", nil),
newTestMemberAsLearner(3, nil, "3", nil),
},
3,
true,
},
{
// 1/2 members ready, should succeed (quorum = 2)
[]*Member{
newTestMember(1, nil, "1", nil),
newTestMember(2, nil, "", nil),
newTestMemberAsLearner(3, nil, "3", nil),
},
3,
true,
},
{
// 1/3 members ready, should fail (quorum = 2)
[]*Member{
newTestMember(1, nil, "1", nil),
newTestMember(2, nil, "", nil),
newTestMember(3, nil, "", nil),
newTestMemberAsLearner(4, nil, "4", nil),
},
4,
false,
},
{
// 2/3 members ready, should succeed (quorum = 2, new quorum = 3)
[]*Member{
newTestMember(1, nil, "1", nil),
newTestMember(2, nil, "2", nil),
newTestMember(3, nil, "", nil),
newTestMemberAsLearner(4, nil, "4", nil),
},
4,
true,
},
{
// 2/4 members ready, should succeed (quorum = 3)
[]*Member{
newTestMember(1, nil, "1", nil),
newTestMember(2, nil, "2", nil),
newTestMember(3, nil, "", nil),
newTestMember(4, nil, "", nil),
newTestMemberAsLearner(5, nil, "5", nil),
},
5,
true,
},
}
for i, tt := range tests {
c := newTestCluster(tt.members)
if got := c.IsReadyToPromoteMember(tt.promoteID); got != tt.want {
t.Errorf("%d: isReadyToPromoteMember returned %t, want %t", i, got, tt.want)
}
}
}