co.cask.cdap.api.dataset.lib.PartitionConsumerState.java Source code

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Here is the source code for co.cask.cdap.api.dataset.lib.PartitionConsumerState.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.cdap.api.dataset.lib;

import com.google.common.base.Preconditions;
import com.google.common.collect.ImmutableList;
import com.google.common.collect.Lists;
import com.google.common.primitives.Longs;

import java.nio.ByteBuffer;
import java.util.Collections;
import java.util.List;

/**
 * Contains the state necessary to keep track of which partitions are processed and which partitions would need to be
 * processed as they are created.
 */
public class PartitionConsumerState {
    // useful on initial query of partitions
    public static final PartitionConsumerState FROM_BEGINNING = new PartitionConsumerState(0,
            Collections.<Long>emptyList());

    // Read pointer of the transaction from the previous query of partitions. This is used to scan for new partitions
    // created since then.
    private final long startVersion;
    // The list of in progress transactions from the previous query of partitions that are smaller than the startVersion.
    // We do not need to include the in-progress transaction Ids that are larger than the startVersion because those will
    // be picked up in the next scan anyways, since we will start the scan from the startVersion.
    // Keeping track of these in-progress transactions is necessary because these might be creations of partitions that
    // fall before the startVersion.
    private final List<Long> versionsToCheck;

    public PartitionConsumerState(long startVersion, List<Long> versionsToCheck) {
        Preconditions.checkNotNull(versionsToCheck);
        this.startVersion = startVersion;
        this.versionsToCheck = ImmutableList.copyOf(versionsToCheck);
    }

    public long getStartVersion() {
        return startVersion;
    }

    public List<Long> getVersionsToCheck() {
        return versionsToCheck;
    }

    public static PartitionConsumerState fromBytes(byte[] bytes) {
        Preconditions.checkArgument((bytes.length - 1) % Longs.BYTES == 0,
                "bytes does not have length divisible by Longs.BYTES");
        ByteBuffer bb = ByteBuffer.wrap(bytes);
        byte serializationFormatVersion = bb.get();
        Preconditions.checkArgument(serializationFormatVersion == 0, "Unsupported serialization format: {}",
                serializationFormatVersion);
        long startVersion = bb.getLong();
        List<Long> versionsToCheck = Lists.newArrayList();
        while (bb.hasRemaining()) {
            versionsToCheck.add(bb.getLong());
        }
        return new PartitionConsumerState(startVersion, versionsToCheck);
    }

    public byte[] toBytes() {
        int numLongs = 1 + versionsToCheck.size();
        // first byte for serialization format version
        ByteBuffer bb = ByteBuffer.allocate(1 + Longs.BYTES * numLongs);
        // currently, serialization format is 0
        bb.put((byte) 0);
        bb.putLong(startVersion);
        for (long l : versionsToCheck) {
            bb.putLong(l);
        }
        return bb.array();
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) {
            return true;
        }
        if (o == null || getClass() != o.getClass()) {
            return false;
        }

        PartitionConsumerState that = (PartitionConsumerState) o;

        if (startVersion != that.startVersion) {
            return false;
        }
        return versionsToCheck.equals(that.versionsToCheck);
    }

    @Override
    public int hashCode() {
        int result = (int) (startVersion ^ (startVersion >>> 32));
        result = 31 * result + versionsToCheck.hashCode();
        return result;
    }
}