eagle-core/eagle-query/eagle-entity-base/src/main/java/org/apache/eagle/log/entity/index/NonClusteredIndexLogReader.java

/*
 * 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.eagle.log.entity.index;

import org.apache.eagle.common.config.EagleConfigFactory;
import org.apache.eagle.log.entity.HBaseInternalLogHelper;
import org.apache.eagle.log.entity.InternalLog;
import org.apache.eagle.log.entity.meta.IndexDefinition;
import org.apache.eagle.common.ByteUtil;
import org.apache.hadoop.hbase.client.*;
import org.apache.hadoop.hbase.filter.Filter;

import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

public class NonClusteredIndexLogReader extends IndexLogReader {
    private final IndexDefinition indexDef;
    private final List<byte[]> indexRowkeys;
    private final byte[][] qualifiers;
    private final Filter filter;
    private HTableInterface tbl;
    private boolean isOpen = false;
    private Result[] results;
    private int index = -1;
    private final List<Scan> scans;
    private int currentScanIndex = 0;
    private ResultScanner currentResultScanner;

    // Max tag key/value.
    private static final byte[] MAX_TAG_VALUE_BYTES = {
        (byte)0XFF, (byte)0XFF, (byte)0XFF, (byte)0XFF,
        (byte)0XFF, (byte)0XFF, (byte)0XFF, (byte)0XFF,
        (byte)0XFF
    };
    private static final int BATCH_MULTIGET_SIZE = 1000;

    public NonClusteredIndexLogReader(IndexDefinition indexDef, List<byte[]> indexRowkeys,
                                      byte[][] qualifiers, Filter filter) {
        this.indexDef = indexDef;
        this.indexRowkeys = indexRowkeys;
        this.qualifiers = qualifiers;
        this.filter = filter;
        this.scans = buildScans();
    }

    private List<Scan> buildScans() {
        final ArrayList<Scan> result = new ArrayList<Scan>(indexRowkeys.size());
        for (byte[] rowkey : indexRowkeys) {
            Scan s = new Scan();
            s.setStartRow(rowkey);
            // In rowkey the tag key/value is sorted by the hash code of the key, so MAX_TAG_VALUE_BYTES is
            // enough as the end key
            final byte[] stopRowkey = ByteUtil.concat(rowkey, MAX_TAG_VALUE_BYTES);
            s.setStopRow(stopRowkey);
            // TODO the # of cached rows should be minimum of (pagesize and 100)
            int cs = EagleConfigFactory.load().getHBaseClientScanCacheSize();
            s.setCaching(cs);
            // TODO not optimized for all applications
            s.setCacheBlocks(true);
            // scan specified columnfamily for all qualifiers
            s.addFamily(indexDef.getEntityDefinition().getColumnFamily().getBytes());
            result.add(s);
        }
        return result;
    }

    @Override
    public void open() throws IOException {
        if (isOpen) {
            return; // silently return
        }
        try {
            tbl = EagleConfigFactory.load().getHTable(indexDef.getEntityDefinition().getTable());
        } catch (RuntimeException ex) {
            throw new IOException(ex);
        }
        currentScanIndex = 0;
        openNewScan();
        fillResults();
    }

    private boolean openNewScan() throws IOException {
        closeCurrentScanResult();
        if (currentScanIndex >= scans.size()) {
            return false;
        }
        final Scan scan = scans.get(currentScanIndex++);
        currentResultScanner = tbl.getScanner(scan);
        return true;
    }

    private void fillResults() throws IOException {
        if (currentResultScanner == null) {
            return;
        }
        index = 0;
        int count = 0;
        Result r = null;
        final List<Get> gets = new ArrayList<Get>(BATCH_MULTIGET_SIZE);
        final byte[] family = indexDef.getEntityDefinition().getColumnFamily().getBytes();
        while (count < BATCH_MULTIGET_SIZE) {
            r = currentResultScanner.next();
            if (r == null) {
                if (openNewScan()) {
                    continue;
                } else {
                    break;
                }
            }
            for (byte[] rowkey : r.getFamilyMap(family).keySet()) {
                if (rowkey.length == 0) { // invalid rowkey
                    continue;
                }
                final Get get = new Get(rowkey);
                if (filter != null) {
                    get.setFilter(filter);
                }
                if (qualifiers != null) {
                    for (int j = 0; j < qualifiers.length; ++j) {
                        // Return the specified qualifiers
                        get.addColumn(family, qualifiers[j]);
                    }
                } else {
                    get.addFamily(family);
                }
                workaroundHBASE2198(get, filter, qualifiers);
                gets.add(get);
                ++count;
            }
        }
        if (count == 0) {
            results = null;
            return;
        }
        results = tbl.get(gets);
        if (results == null || results.length == 0) {
            fillResults();
        }
    }

    private void closeCurrentScanResult() {
        if (currentResultScanner != null) {
            currentResultScanner.close();
            currentResultScanner = null;
        }
    }

    @Override
    public void close() throws IOException {
        if (tbl != null) {
            new HTableFactory().releaseHTableInterface(tbl);
        }
        closeCurrentScanResult();
    }

    @Override
    public InternalLog read() throws IOException {
        if (tbl == null) {
            throw new IllegalArgumentException("Haven't open before reading");
        }

        Result r = null;
        InternalLog t = null;
        while ((r = getNextResult()) != null) {
            if (r.getRow() == null) {
                continue;
            }
            t = HBaseInternalLogHelper.parse(indexDef.getEntityDefinition(), r, qualifiers);
            break;
        }
        return t;
    }

    private Result getNextResult() throws IOException {
        if (results == null || results.length == 0 || index >= results.length) {
            fillResults();
        }
        if (results == null || results.length == 0 || index >= results.length) {
            return null;
        }
        return results[index++];
    }

}