org.apache.tephra.visibility.ReadFence.java Source code

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Here is the source code for org.apache.tephra.visibility.ReadFence.java

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/*
 * Licensed to the Apache Software Foundation (ASF) under one
 * or more contributor license agreements.  See the NOTICE file
 * distributed with this work for additional information
 * regarding copyright ownership.  The ASF licenses this file
 * to you 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 org.apache.tephra.visibility;

import com.google.common.primitives.Bytes;
import com.google.common.primitives.Longs;
import org.apache.tephra.Transaction;
import org.apache.tephra.TransactionAware;

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();
    }
}