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rafttest: reduce waitLeader flakiness #195

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rafttest: reduce waitLeader flakiness #195

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41 changes: 23 additions & 18 deletions rafttest/node_test.go
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Original file line number Diff line number Diff line change
Expand Up @@ -35,7 +35,7 @@ func TestBasicProgress(t *testing.T) {
nodes = append(nodes, n)
}

waitLeader(nodes)
waitStableLeader(nodes)
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@pav-kv pav-kv Apr 10, 2024 •
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Maybe a better fix for this test, specifically, would be to relax the expectation in line 44 that all 100 entries are committed. In fact, we don't have any guarantee that any entry is going to be committed. If the leader election is completely unstable, and every single submitted entry that gets routed to a now-leader ends up wiped because there is already a higher-term leader, we won't commit anything.

We can require in this test, however, that most entries are committed (say, at least 70 out of 100), to demonstrate that there is liveness in this implementation.

Alternatively, once we have a leader, we can stop ticking the nodes, so that no re-election will occur and disrupt the 100 entries flow.


for i := 0; i < 100; i++ {
nodes[0].Propose(context.TODO(), []byte("somedata"))
Expand All @@ -59,7 +59,7 @@ func TestRestart(t *testing.T) {
nodes = append(nodes, n)
}

l := waitLeader(nodes)
l := waitStableLeader(nodes)
k1, k2 := (l+1)%5, (l+2)%5

for i := 0; i < 30; i++ {
Expand Down Expand Up @@ -97,7 +97,7 @@ func TestPause(t *testing.T) {
nodes = append(nodes, n)
}

waitLeader(nodes)
waitStableLeader(nodes)

for i := 0; i < 30; i++ {
nodes[0].Propose(context.TODO(), []byte("somedata"))
Expand All @@ -123,26 +123,31 @@ func TestPause(t *testing.T) {
}
}

func waitLeader(ns []*node) int {
var l map[uint64]struct{}
var lindex = -1

// waitStableLeader waits until there is a stable leader in the cluster. It
// heuristically assumes that there is a stable leader when there is a node in
// StateLeader among the highest-term nodes.
//
// Note that this function would not work properly in clusters with "network"
// partitions, in which a node can have the highest term, and yet never become a
// leader.
func waitStableLeader(ns []*node) int {
for {
l = make(map[uint64]struct{})

lead := -1
var maxTerm uint64
for i, n := range ns {
lead := n.Status().SoftState.Lead
if lead != 0 {
l[lead] = struct{}{}
if n.id == lead {
lindex = i
}
st := n.Status()
if st.Term > maxTerm {
lead = -1
maxTerm = st.Term
}
if st.RaftState == raft.StateLeader {
lead = i
}
}

if len(l) == 1 && lindex != -1 {
return lindex
if lead != -1 {
return lead
}
time.Sleep(time.Millisecond)
}
}

Expand Down
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