com.qubole.rubix.core.ReadRequestChain.java Source code

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Here is the source code for com.qubole.rubix.core.ReadRequestChain.java

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/**
 * Copyright (c) 2016. Qubole 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. See accompanying LICENSE file.
 */
package com.qubole.rubix.core;

import com.google.common.annotations.VisibleForTesting;
import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Callable;

import static com.google.common.base.Preconditions.checkState;

/**
 * Created by stagra on 4/1/16.
 *
 * One ReadRequestChain contains ReadRequests for same buffer
 */
public abstract class ReadRequestChain implements Callable<Integer> {
    List<ReadRequest> readRequests = new ArrayList<ReadRequest>();
    ReadRequest lastRequest = null;
    boolean isLocked = false;

    protected String threadName;
    protected long requests = 0;

    private static final Log log = LogFactory.getLog(ReadRequestChain.class);

    public ReadRequestChain() {
        super();
        this.threadName = Thread.currentThread().getName();
    }

    // Should be added in forward seek fashion for better performance
    public void addReadRequest(ReadRequest readRequest) {
        checkState(!isLocked, "Adding request to a locked chain");
        log.debug(
                String.format("Request to add ReadRequest: [%d, %d, %d, %d, %d]", readRequest.getBackendReadStart(),
                        readRequest.getBackendReadEnd(), readRequest.getActualReadStart(),
                        readRequest.getActualReadEnd(), readRequest.getDestBufferOffset()));
        if (lastRequest == null) {
            addRequest(readRequest);
        } else {
            // since one chain contains request of same buffer, we can collate
            if (lastRequest.getBackendReadEnd() == readRequest.getBackendReadStart()) {
                // Since the ReadRequests coming in are for same buffer, can merge the two
                lastRequest.setBackendReadEnd(readRequest.getBackendReadEnd());
                lastRequest.setActualReadEnd(readRequest.getActualReadEnd());
                log.debug(String.format("Updated last to: [%d, %d, %d, %d, %d]", lastRequest.getBackendReadStart(),
                        lastRequest.getBackendReadEnd(), lastRequest.getActualReadStart(),
                        lastRequest.getActualReadEnd(), lastRequest.getDestBufferOffset()));
            } else {
                addRequest(readRequest);
            }
        }
        requests++;
    }

    private void addRequest(ReadRequest readRequest) {
        readRequests.add(readRequest);
        lastRequest = readRequest;
        log.debug(String.format("Added ReadRequest: [%d, %d, %d, %d, %d]", readRequest.getBackendReadStart(),
                readRequest.getBackendReadEnd(), readRequest.getActualReadStart(), readRequest.getActualReadEnd(),
                readRequest.getDestBufferOffset()));
    }

    public void lock() {
        isLocked = true;
    }

    @VisibleForTesting
    public List<ReadRequest> getReadRequests() {
        return readRequests;
    }

    public abstract ReadRequestChainStats getStats();

    /*
     * This method is used called to update the cache status after read has been done
     */
    public void updateCacheStatus(String remotePath, long fileSize, long lastModified, int blockSize,
            Configuration conf) {
        // no-op by default
    }
}