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Fix #943: don't try to take 2 snapshots at a time #1081

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Fix #943: don't try to take 2 snapshots at a time #1081

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2 changes: 2 additions & 0 deletions _vendor/raft/server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -1203,6 +1203,7 @@ func (s *server) TakeSnapshot() error {

state, err := s.stateMachine.Save()
if err != nil {
s.pendingSnapshot = nil
return err
}

Expand Down Expand Up @@ -1237,6 +1238,7 @@ func (s *server) saveSnapshot() error {

// Write snapshot to disk.
if err := s.pendingSnapshot.save(); err != nil {
s.pendingSnapshot = nil
return err
}

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13 changes: 13 additions & 0 deletions _vendor/raft/snapshot_test.go
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Original file line number Diff line number Diff line change
@@ -1,6 +1,7 @@
package raft

import (
"errors"
"fmt"
"io/ioutil"
"os"
Expand Down Expand Up @@ -121,6 +122,18 @@ func TestSnapshotRequest(t *testing.T) {
})
}

func TestTakeSnapshotWhenStateMachineSaveFails(t *testing.T) {
runServerWithMockStateMachine(Leader, func(s Server, m *mock.Mock) {
m.On("Save").Return([]byte("foo"), errors.New("test error message"))

s.Do(&testCommand1{})
err := s.TakeSnapshot()
assert.Equal(t, err.Error(), "test error message")
assert.Nil(t, s.(*server).pendingSnapshot)
s.Stop()
})
}

func runServerWithMockStateMachine(state string, fn func(s Server, m *mock.Mock)) {
var m mockStateMachine
s := newTestServer("1", &testTransporter{})
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2 changes: 2 additions & 0 deletions coordinator/raft_server.go
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Original file line number Diff line number Diff line change
Expand Up @@ -331,6 +331,8 @@ const (
)

func (s *RaftServer) ForceLogCompaction() error {
s.mutex.Lock()
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Why this change?

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Without the lock, influxdb attempts to take multiple snapshots at the same time. If you comment those lines out, rebuild influxdb, and then run it & influxdb_stress (described above) at the same time...you'll see the messages in the log.

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OK, got it, I was thinking that might be it from the title of the PR. I guess I might have put the lock inside TakeSnapshot(). This is kind of a matter of taste though -- depends on one thinks about TakeSnapshot().

defer s.mutex.Unlock()
err := s.raftServer.TakeSnapshot()
if err != nil {
log.Error("Cannot take snapshot: %s", err)
Expand Down