// Indirectly this tests that the transaction remembers the NodeID of the node
// being read from correctly, at least in this simple case. Not remembering the
// node would lead to thousands of transaction restarts and almost certainly a
// test timeout.
func TestUncertaintyRestarts(t *testing.T) {
defer leaktest.AfterTest(t)
s := createTestDB(t)
defer s.Stop()
// Set a large offset so that a busy restart-loop
// really shows. Also makes sure that the values
// we write in the future below don't actually
// wind up in the past.
offset := 4000 * time.Millisecond
s.Clock.SetMaxOffset(offset)
key := roachpb.Key("key")
value := roachpb.Value{
Bytes: nil, // Set for each Put
}
// With the correct restart behaviour, we see only one restart
// and the value read is the very first one (as nothing else
// has been written)
wantedBytes := []byte("value-0")
i := -1
tErr := s.DB.Txn(func(txn *client.Txn) error {
i++
s.Manual.Increment(1)
futureTS := s.Clock.Now()
futureTS.WallTime++
value.Bytes = []byte(fmt.Sprintf("value-%d", i))
if err := engine.MVCCPut(s.Eng, nil, key, futureTS, value, nil); err != nil {
t.Fatal(err)
}
gr, err := txn.Get(key)
if err != nil {
return err
}
if !gr.Exists() || !bytes.Equal(gr.ValueBytes(), wantedBytes) {
t.Fatalf("%d: read wrong value: %v, wanted %q", i, gr.Value, wantedBytes)
}
return nil
})
if i != 1 {
t.Errorf("txn restarted %d times, expected only one restart", i)
}
if tErr != nil {
t.Fatal(tErr)
}
}