package azkaban.common.web;
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.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);
@Override
public boolean canReadFile(FileSystem fs, Path path) {
if(logger.isDebugEnabled())
logger.debug("path:" + path.toUri().getPath());
try {
DataFileStream<Object> avroDataStream = getAvroDataStream(fs, path);
Schema schema = avroDataStream.getSchema();
avroDataStream.close();
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;
}
}
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 = fs.open(path);
return new DataFileStream<Object>(hdfsInputStream, avroReader);
}
@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;
try {
avroDatastream = getAvroDataStream(fs, path);
Schema schema = avroDatastream.getSchema();
DatumWriter<Object> avroWriter = new GenericDatumWriter<Object>(schema);
JsonGenerator g = new JsonFactory().createJsonGenerator(outputStream, JsonEncoding.UTF8);
g.useDefaultPrettyPrinter();
Encoder encoder = new JsonEncoder(schema, g);
int lineno = 1; // line number starts from 1
while(avroDatastream.hasNext() && lineno <= endLine) {
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 {
avroDatastream.close();
}
}
}