azkaban.viewer.hdfs.HdfsAvroFileViewer.java Source code

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Here is the source code for azkaban.viewer.hdfs.HdfsAvroFileViewer.java

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/*
 * Copyright 2012 LinkedIn Corp.
 * 
 * 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 azkaban.viewer.hdfs;

import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;

import org.apache.avro.Schema;
import org.apache.avro.file.DataFileStream;
import org.apache.avro.generic.GenericDatumReader;
import org.apache.avro.generic.GenericDatumWriter;
import org.apache.avro.io.DatumWriter;
import org.apache.avro.io.Encoder;
import org.apache.avro.io.EncoderFactory;
import org.apache.avro.io.JsonEncoder;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.log4j.Logger;
import org.codehaus.jackson.JsonEncoding;
import org.codehaus.jackson.JsonFactory;
import org.codehaus.jackson.JsonGenerator;

/**
 * This class implements a viewer of avro files
 * 
 * @author lguo
 * 
 */
public class HdfsAvroFileViewer implements HdfsFileViewer {

    private static Logger logger = Logger.getLogger(HdfsAvroFileViewer.class);
    // Will spend 5 seconds trying to pull data and then stop.
    private static long STOP_TIME = 2000l;

    @Override
    public boolean canReadFile(FileSystem fs, Path path) {

        if (logger.isDebugEnabled())
            logger.debug("path:" + path.toUri().getPath());

        DataFileStream<Object> avroDataStream = null;
        try {
            avroDataStream = getAvroDataStream(fs, path);
            Schema schema = avroDataStream.getSchema();
            return schema != null;
        } catch (IOException e) {
            if (logger.isDebugEnabled()) {
                logger.debug(path.toUri().getPath() + " is not an avro file.");
                logger.debug("Error in getting avro schema: " + e.getLocalizedMessage());
            }
            return false;
        } finally {
            try {
                if (avroDataStream != null) {
                    avroDataStream.close();
                }
            } catch (IOException e) {
                logger.error(e);
            }
        }
    }

    private DataFileStream<Object> getAvroDataStream(FileSystem fs, Path path) throws IOException {
        if (logger.isDebugEnabled())
            logger.debug("path:" + path.toUri().getPath());

        GenericDatumReader<Object> avroReader = new GenericDatumReader<Object>();
        InputStream hdfsInputStream = null;
        try {
            hdfsInputStream = fs.open(path);
        } catch (Exception e) {
            if (hdfsInputStream != null) {
                hdfsInputStream.close();
            }
        }

        DataFileStream<Object> avroDataFileStream = null;
        try {
            avroDataFileStream = new DataFileStream<Object>(hdfsInputStream, avroReader);
        } catch (IOException e) {
            if (hdfsInputStream != null) {
                hdfsInputStream.close();
            }
            throw e;
        }

        return avroDataFileStream;
    }

    @Override
    public void displayFile(FileSystem fs, Path path, OutputStream outputStream, int startLine, int endLine)
            throws IOException {

        if (logger.isDebugEnabled())
            logger.debug("display avro file:" + path.toUri().getPath());

        DataFileStream<Object> avroDatastream = null;
        JsonGenerator g = null;

        try {
            avroDatastream = getAvroDataStream(fs, path);
            Schema schema = avroDatastream.getSchema();
            DatumWriter<Object> avroWriter = new GenericDatumWriter<Object>(schema);

            g = new JsonFactory().createJsonGenerator(outputStream, JsonEncoding.UTF8);
            g.useDefaultPrettyPrinter();
            Encoder encoder = EncoderFactory.get().jsonEncoder(schema, g);

            long endTime = System.currentTimeMillis() + STOP_TIME;
            int lineno = 1; // line number starts from 1
            while (avroDatastream.hasNext() && lineno <= endLine && System.currentTimeMillis() <= endTime) {
                Object datum = avroDatastream.next();
                if (lineno >= startLine) {
                    String record = "\n\n Record " + lineno + ":\n";
                    outputStream.write(record.getBytes("UTF-8"));
                    avroWriter.write(datum, encoder);
                    encoder.flush();
                }
                lineno++;
            }
        } catch (IOException e) {
            outputStream.write(("Error in display avro file: " + e.getLocalizedMessage()).getBytes("UTF-8"));
            throw e;
        } finally {
            if (g != null) {
                g.close();
            }
            avroDatastream.close();
        }
    }

}