Ejemplo n.º 1
0
// beginCmd waits for any overlapping, already-executing commands via
// the command queue and adds itself to the queue to gate follow-on
// commands which overlap its key range. This method will block if
// there are any overlapping commands already in the queue. Returns
// the command queue insertion key, to be supplied to subsequent
// invocation of endCmd().
func (r *Range) beginCmd(header *proto.RequestHeader, readOnly bool) interface{} {
	r.Lock()
	var wg sync.WaitGroup
	r.cmdQ.GetWait(header.Key, header.EndKey, readOnly, &wg)
	cmdKey := r.cmdQ.Add(header.Key, header.EndKey, readOnly)
	r.Unlock()
	wg.Wait()
	// Update the incoming timestamp if unset. Wait until after any
	// preceding command(s) for key range are complete so that the node
	// clock has been updated to the high water mark of any commands
	// which might overlap this one in effect.
	if header.Timestamp.Equal(proto.ZeroTimestamp) {
		header.Timestamp = r.rm.Clock().Now()
	}
	return cmdKey
}
Ejemplo n.º 2
0
// TestTxnPutOutOfOrder tests a case where a put operation of an older
// timestamp comes after a put operation of a newer timestamp in a
// txn. The test ensures such an out-of-order put succeeds and
// overrides an old value. The test uses a "Writer" and a "Reader"
// to reproduce an out-of-order put.
//
// 1) The Writer executes a put operation and writes a write intent with
//    time T in a txn.
// 2) Before the Writer's txn is committed, the Reader sends a high priority
//    get operation with time T+100. This pushes the Writer txn timestamp to
//    T+100 and triggers the restart of the Writer's txn. The original
//    write intent timestamp is also updated to T+100.
// 3) The Writer starts a new epoch of the txn, but before it writes, the
//    Reader sends another high priority get operation with time T+200. This
//    pushes the Writer txn timestamp to T+200 to trigger a restart of the
//    Writer txn. The Writer will not actually restart until it tries to commit
//    the current epoch of the transaction. The Reader updates the timestamp of
//    the write intent to T+200. The test deliberately fails the Reader get
//    operation, and cockroach doesn't update its read timestamp cache.
// 4) The Writer executes the put operation again. This put operation comes
//    out-of-order since its timestamp is T+100, while the intent timestamp
//    updated at Step 3 is T+200.
// 5) The put operation overrides the old value using timestamp T+100.
// 6) When the Writer attempts to commit its txn, the txn will be restarted
//    again at a new epoch timestamp T+200, which will finally succeed.
func TestTxnPutOutOfOrder(t *testing.T) {
	defer leaktest.AfterTest(t)

	key := "key"
	// Set up a filter to so that the get operation at Step 3 will return an error.
	var numGets int32
	storage.TestingCommandFilter = func(args proto.Request) error {
		if _, ok := args.(*proto.GetRequest); ok &&
			args.Header().Key.Equal(proto.Key(key)) &&
			args.Header().Txn == nil {
			// The Reader executes two get operations, each of which triggers two get requests
			// (the first request fails and triggers txn push, and then the second request
			// succeeds). Returns an error for the fourth get request to avoid timestamp cache
			// update after the third get operation pushes the txn timestamp.
			if atomic.AddInt32(&numGets, 1) == 4 {
				return util.Errorf("Test")
			}
		}
		return nil
	}
	defer func() {
		storage.TestingCommandFilter = nil
	}()

	manualClock := hlc.NewManualClock(0)
	clock := hlc.NewClock(manualClock.UnixNano)
	store, stopper := createTestStoreWithEngine(t,
		engine.NewInMem(proto.Attributes{}, 10<<20),
		clock,
		true,
		nil)
	defer stopper.Stop()

	// Put an initial value.
	initVal := []byte("initVal")
	err := store.DB().Put(key, initVal)
	if err != nil {
		t.Fatalf("failed to put: %s", err)
	}

	waitPut := make(chan struct{})
	waitFirstGet := make(chan struct{})
	waitTxnRestart := make(chan struct{})
	waitSecondGet := make(chan struct{})
	waitTxnComplete := make(chan struct{})

	// Start the Writer.
	go func() {
		epoch := -1
		// Start a txn that does read-after-write.
		// The txn will be restarted twice, and the out-of-order put
		// will happen in the second epoch.
		if err := store.DB().Txn(func(txn *client.Txn) error {
			epoch++

			if epoch == 1 {
				// Wait until the second get operation is issued.
				close(waitTxnRestart)
				<-waitSecondGet
			}

			updatedVal := []byte("updatedVal")
			if err := txn.Put(key, updatedVal); err != nil {
				return err
			}

			// Make sure a get will return the value that was just written.
			actual, err := txn.Get(key)
			if err != nil {
				return err
			}
			if !bytes.Equal(actual.ValueBytes(), updatedVal) {
				t.Fatalf("unexpected get result: %s", actual)
			}

			if epoch == 0 {
				// Wait until the first get operation will push the txn timestamp.
				close(waitPut)
				<-waitFirstGet
			}

			b := &client.Batch{}
			err = txn.Commit(b)
			return err
		}); err != nil {
			t.Fatal(err)
		}

		if epoch != 2 {
			t.Fatalf("unexpected number of txn retries: %d", epoch)
		}

		close(waitTxnComplete)
	}()

	<-waitPut

	// Start the Reader.

	// Advance the clock and send a get operation with higher
	// priority to trigger the txn restart.
	manualClock.Increment(100)

	priority := int32(math.MaxInt32)
	requestHeader := proto.RequestHeader{
		Key:          proto.Key(key),
		RaftID:       1,
		Replica:      proto.Replica{StoreID: store.StoreID()},
		UserPriority: &priority,
		Timestamp:    clock.Now(),
	}
	getCall := proto.Call{
		Args: &proto.GetRequest{
			RequestHeader: requestHeader,
		},
		Reply: &proto.GetResponse{},
	}
	err = store.ExecuteCmd(context.Background(), getCall)
	if err != nil {
		t.Fatalf("failed to get: %s", err)
	}

	// Wait until the writer restarts the txn.
	close(waitFirstGet)
	<-waitTxnRestart

	// Advance the clock and send a get operation again. This time
	// we use TestingCommandFilter so that a get operation is not
	// processed after the write intent is resolved (to prevent the
	// timestamp cache from being updated).
	manualClock.Increment(100)

	requestHeader.Timestamp = clock.Now()
	getCall = proto.Call{
		Args: &proto.GetRequest{
			RequestHeader: requestHeader,
		},
		Reply: &proto.GetResponse{},
	}

	err = store.ExecuteCmd(context.Background(), getCall)
	if err == nil {
		t.Fatal("unexpected success of get")
	}

	close(waitSecondGet)
	<-waitTxnComplete
}