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Hadoop Connector for Microsoft Azure DocumentDB
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//------------------------------------------------------------
// Copyright (c) Microsoft Corporation.  All rights reserved.
//------------------------------------------------------------
package com.microsoft.azure.documentdb.hadoop;

import java.io.DataInput;
import java.io.DataOutput;
import java.io.IOException;
import java.util.Arrays;
import java.util.Iterator;
import java.util.LinkedList;
import java.util.List;

import org.apache.commons.logging.Log;
import org.apache.commons.logging.LogFactory;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.io.Text;
import org.apache.hadoop.io.Writable;
import org.apache.hadoop.mapreduce.InputSplit;

import com.microsoft.azure.documentdb.ConnectionPolicy;
import com.microsoft.azure.documentdb.ConsistencyLevel;
import com.microsoft.azure.documentdb.Database;
import com.microsoft.azure.documentdb.Document;
import com.microsoft.azure.documentdb.DocumentClient;
import com.microsoft.azure.documentdb.DocumentCollection;
import com.microsoft.azure.documentdb.FeedOptions;
import com.microsoft.azure.documentdb.QueryIterable;
import com.microsoft.azure.documentdb.SqlParameter;
import com.microsoft.azure.documentdb.SqlParameterCollection;
import com.microsoft.azure.documentdb.SqlQuerySpec;

/**
 * An input split that represents one collection from documentdb. It reads data one page at a time and
 * sends one by one document to the mapper.
 * In order to be able to use it, you need to set the required configuration properties for the input split. 
 */
public class DocumentDBInputSplit extends InputSplit implements Writable, org.apache.hadoop.mapred.InputSplit {

    private static final Log LOG = LogFactory.getLog(DocumentDBWritable.class);
    private final int MAX_PAGE_SIZE = 700;
    private Text host, key, dbName, collName, query;
    private Iterator documentIterator;

    public DocumentDBInputSplit() {
        this.host = new Text();
        this.key = new Text();
        this.dbName = new Text();
        this.collName = new Text();
        this.query = new Text();
    }

    public DocumentDBInputSplit(String host, String key, String dbName, String collName, String query) {
        this.host = new Text(host);
        this.key = new Text(key);
        this.dbName = new Text(dbName);
        this.collName = new Text(collName);
        if (query == null) {
            query = "";
        }

        this.query = new Text(query);
    }

    /**
     * Gets the list of DocumentDBInputSplit used.
     */
    public static List getSplits(Configuration conf, String dbHost, String dbKey, String dbName,
            String[] collNames, String query) {
        int internalNumSplits = collNames.length;
        List splits = new LinkedList();
        for (int i = 0; i < internalNumSplits; i++) {
            splits.add(new DocumentDBInputSplit(dbHost, dbKey, dbName, collNames[i].trim(), query));
        }
        
        return splits;
    }

    /**
     * @inheritDoc
     */
    @Override
    public long getLength() {
        return Integer.MAX_VALUE;
    }

    /**
     * @inheritDoc
     */
    @Override
    public String[] getLocations() throws IOException {
        // Since we're pulling the data from DocumentDB, it's not localized
        // to any single node so just return localhost.
        return new String[] { "localhost" };
    }

    public String getCollectionName() {
        return this.collName.toString();
    }

    /**
     * @inheritDoc
     */
    public void readFields(DataInput in) throws IOException {
        this.host.readFields(in);
        this.key.readFields(in);
        this.dbName.readFields(in);
        this.collName.readFields(in);
        this.query.readFields(in);
    }

    /**
     * @inheritDoc
     */
    public void write(DataOutput out) throws IOException {
        this.host.write(out);
        this.key.write(out);
        this.dbName.write(out);
        this.collName.write(out);
        this.query.write(out);
    }

    /**
     * 
     * @return an Iterator for documents in the collection wrapped by the split.
     * @throws IOException if a read operation fails on documentdb
     */
    public Iterator getDocumentIterator() throws IOException {
        if (this.documentIterator != null)
            return this.documentIterator;

        Database db;
        DocumentCollection coll;
        DocumentClient client;
        try {
            LOG.debug("Connecting to " + this.host + " and reading from collection " + this.collName);
            ConnectionPolicy policy = ConnectionPolicy.GetDefault();
            policy.setUserAgentSuffix(DocumentDBConnectorUtil.UserAgentSuffix);
            client = new DocumentClient(this.host.toString(), this.key.toString(), policy,
                    ConsistencyLevel.Session);
            
            db = DocumentDBConnectorUtil.GetDatabase(client, this.dbName.toString());
            if (db == null) {
                throw new IOException(String.format("Database %s doesn't exist", this.dbName));
            }

            coll = DocumentDBConnectorUtil.GetDocumentCollection(client, db.getSelfLink(), this.collName.toString());
            if (coll == null) {
                throw new IOException(String.format("collection %s doesn't exist", this.collName));
            }

            String query = this.query.toString();
            if (query != null && !query.isEmpty()) {
                query = this.query.toString();
            } else {
                query = "select * from root";
            }

            FeedOptions options = new FeedOptions();
            options.setPageSize(MAX_PAGE_SIZE);
            this.documentIterator = client.queryDocuments(
                    coll.getSelfLink(),
                    query,
                    options).getQueryIterator();
        } catch (Exception e) {
            throw new IOException(e);
        }

        return this.documentIterator;
    }

    public String toString() {
        return String.format("DocumentDBSplit(collection=%s)", this.collName);
    }

}