co.cask.tephra.visibility.WriteFence.java Source code

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Here is the source code for co.cask.tephra.visibility.WriteFence.java

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/*
 * 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 com.google.common.primitives.UnsignedBytes;

import java.util.Collection;
import java.util.TreeSet;

/**
 * Implementation used by {@link FenceWait} to wait for a {@link VisibilityFence}.
 */
class WriteFence implements TransactionAware {
    private final byte[] fenceId;
    private Transaction tx;
    private Collection<byte[]> inProgressChanges;

    public WriteFence(byte[] fenceId) {
        this.fenceId = fenceId;
    }

    @Override
    public void startTx(Transaction tx) {
        this.tx = tx;
        if (inProgressChanges == null) {
            inProgressChanges = new TreeSet<>(UnsignedBytes.lexicographicalComparator());
            for (long inProgressTx : tx.getInProgress()) {
                inProgressChanges.add(Bytes.concat(fenceId, Longs.toByteArray(inProgressTx)));
            }
        }
    }

    @Override
    public void updateTx(Transaction tx) {
        // Fences only need original transaction
    }

    @Override
    public Collection<byte[]> getTxChanges() {
        if (inProgressChanges == null || tx == null) {
            throw new IllegalStateException("Transaction has not started yet");
        }
        return inProgressChanges;
    }

    @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();
    }
}