/*
* Copyright © 2015 Cask Data, Inc.
*
* Licensed under the Apache License, Version 2.0 (the "License"); you may not
* use this file except in compliance with the License. You may obtain a copy of
* the License at
*
* http://www.apache.org/licenses/LICENSE-2.0
*
* Unless required by applicable law or agreed to in writing, software
* distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
* WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
* License for the specific language governing permissions and limitations under
* the License.
*/
package co.cask.tephra.visibility;
import co.cask.tephra.Transaction;
import co.cask.tephra.TransactionAware;
import com.google.common.primitives.Bytes;
import com.google.common.primitives.Longs;
import java.util.Collection;
import java.util.Collections;
/**
* Implementation of {@link VisibilityFence} used by reader.
*/
class ReadFence implements TransactionAware {
private final byte[] fenceId;
private Transaction tx;
public ReadFence(byte[] fenceId) {
this.fenceId = fenceId;
}
@Override
public void startTx(Transaction tx) {
this.tx = tx;
}
@Override
public void updateTx(Transaction tx) {
// Fences only need original transaction
}
@Override
public Collection<byte[]> getTxChanges() {
if (tx == null) {
throw new IllegalStateException("Transaction has not started yet");
}
return Collections.singleton(Bytes.concat(fenceId, Longs.toByteArray(tx.getTransactionId())));
}
@Override
public boolean commitTx() throws Exception {
// Nothing to persist
return true;
}
@Override
public void postTxCommit() {
tx = null;
}
@Override
public boolean rollbackTx() throws Exception {
// Nothing to rollback
return true;
}
@Override
public String getTransactionAwareName() {
return getClass().getSimpleName();
}
}