fix liveness issue when leader's disk stalls #683
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,147 @@ | ||
| // Copyright IBM Corp. 2013, 2026 | ||
| // SPDX-License-Identifier: MPL-2.0 | ||
|
|
||
| package raft | ||
|
|
||
| import ( | ||
| "context" | ||
| "fmt" | ||
| "sync" | ||
| "sync/atomic" | ||
| "testing" | ||
| "time" | ||
|
|
||
| "github.com/stretchr/testify/require" | ||
| ) | ||
|
|
||
| func TestLeaderHeartbeatsWithStalledDisk(t *testing.T) { | ||
| c := MakeClusterCustom(t, &MakeClusterOpts{ | ||
| Peers: 3, | ||
| Bootstrap: true, | ||
| LogstoreWrapperFunc: newBlockingLogStore, | ||
| }) | ||
| t.Cleanup(c.Close) | ||
|
|
||
| go func() { | ||
| i := 0 | ||
| ticker := time.NewTicker(500 * time.Millisecond) | ||
| for { | ||
| select { | ||
| case <-t.Context().Done(): | ||
| return | ||
| case <-ticker.C: | ||
| i++ | ||
| leader := c.Leader() | ||
| fut := leader.Apply(fmt.Appendf([]byte{}, "test%d", i), 0) | ||
| if err := fut.Error(); err != nil { | ||
| t.Logf("got error trying to write: %v", err) | ||
| } else { | ||
| t.Logf("write %d ok", i) | ||
| } | ||
| } | ||
| } | ||
| }() | ||
|
|
||
| t.Log("waiting for 5 seconds before partitioning leader") | ||
| time.Sleep(time.Second * 5) | ||
|
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| oldLeader := c.Leader() | ||
| oldLeaderID := oldLeader.leaderID | ||
| oldLeaderTerm := oldLeader.getCurrentTerm() | ||
| c.Partition([]ServerAddress{c.Leader().localAddr}) | ||
|
|
||
| var newLeaderTerm uint64 | ||
| ctx, cancel := context.WithTimeout(t.Context(), 10*c.propagateTimeout) | ||
| t.Cleanup(cancel) | ||
| DONE: | ||
| for { | ||
| select { | ||
| case <-ctx.Done(): | ||
| t.Fatal("election didn't happen!") | ||
| default: | ||
| newLeader := c.Leader() | ||
| if newLeader.leaderID != oldLeaderID { | ||
| t.Log("leader has stepped down!") | ||
| newLeaderTerm = newLeader.getCurrentTerm() | ||
| require.NotEqual(t, newLeaderTerm, oldLeaderTerm) | ||
| cancel() | ||
| break DONE | ||
| } | ||
| } | ||
| } | ||
|
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| require.Len(t, c.WaitForFollowers(1), 1) | ||
|
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| t.Log("leader was elected. healing parition") | ||
|
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| // reconnect the partitioned node | ||
| c.FullyConnect() | ||
| time.Sleep(3 * c.propagateTimeout) | ||
|
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| leaderTerm := c.Leader().getCurrentTerm() | ||
| require.Equal(t, newLeaderTerm, leaderTerm) | ||
|
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| t.Log("blocking disk on leader") | ||
|
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| leader := c.Leader() | ||
| leaderID := leader.leaderID | ||
| leaderStore := leader.logs.(*blockingLogStore) | ||
| leaderStore.block() | ||
| t.Cleanup(leaderStore.unblock) | ||
|
|
||
| ctx, cancel = context.WithTimeout(t.Context(), 5*time.Second) | ||
| t.Cleanup(cancel) | ||
| for { | ||
| select { | ||
| case <-ctx.Done(): | ||
| t.Fatal("leader did not step down!") | ||
| default: | ||
| if c.Leader().leaderID != leaderID { | ||
| t.Log("leader has stepped down!") | ||
| return | ||
| } | ||
| } | ||
| } | ||
| } | ||
|
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||
| // blockingLogStore wraps a LogStore and blocks GetLog calls on demand, | ||
| // simulating disk IO stalls. | ||
| type blockingLogStore struct { | ||
| LogStore | ||
| mu sync.Mutex | ||
| blocked atomic.Bool | ||
| unblockC chan struct{} | ||
| } | ||
|
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||
| func newBlockingLogStore(inner LogStore) LogStore { | ||
| return &blockingLogStore{ | ||
| LogStore: inner, | ||
| unblockC: make(chan struct{}), | ||
| } | ||
| } | ||
|
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| func (b *blockingLogStore) block() { | ||
| b.mu.Lock() | ||
| defer b.mu.Unlock() | ||
| b.blocked.Store(true) | ||
| b.unblockC = make(chan struct{}) | ||
| } | ||
|
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| func (b *blockingLogStore) unblock() { | ||
| b.mu.Lock() | ||
| defer b.mu.Unlock() | ||
| if b.blocked.Load() { | ||
| b.blocked.Store(false) | ||
| close(b.unblockC) | ||
| } | ||
| } | ||
|
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| func (b *blockingLogStore) GetLog(index uint64, log *Log) error { | ||
| if b.blocked.Load() { | ||
| b.mu.Lock() | ||
| ch := b.unblockC | ||
| b.mu.Unlock() | ||
| <-ch | ||
| } | ||
| return b.LogStore.GetLog(index, log) | ||
| } |
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Since the critical section is only a load or store, we could use a
sync.Pointerinstead. Your choice matches existing code (lastContact) though, so either way is fine.