/**
* 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.drill.exec.store.parquet;
import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.util.Arrays;
import java.util.List;
import org.apache.commons.lang3.ArrayUtils;
import org.apache.drill.exec.store.TimedRunnable;
import org.apache.drill.exec.store.dfs.DrillPathFilter;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.fs.FSDataInputStream;
import org.apache.hadoop.fs.FileStatus;
import org.apache.hadoop.fs.FileSystem;
import org.apache.hadoop.fs.Path;
import org.apache.parquet.bytes.BytesUtils;
import org.apache.parquet.hadoop.Footer;
import org.apache.parquet.hadoop.ParquetFileReader;
import org.apache.parquet.hadoop.ParquetFileWriter;
import org.apache.parquet.hadoop.metadata.ParquetMetadata;
import com.google.common.base.Preconditions;
import com.google.common.collect.Lists;
public class FooterGatherer {
static final org.slf4j.Logger logger = org.slf4j.LoggerFactory.getLogger(FooterGatherer.class);
private static final int DEFAULT_READ_SIZE = 64*1024;
private static final int FOOTER_LENGTH_SIZE = 4;
private static final int FOOTER_METADATA_SIZE = FOOTER_LENGTH_SIZE + ParquetFileWriter.MAGIC.length;
private static final int MAGIC_LENGTH = ParquetFileWriter.MAGIC.length;
private static final int MIN_FILE_SIZE = ParquetFileWriter.MAGIC.length + FOOTER_METADATA_SIZE;
private static final void readFully(FSDataInputStream stream, long start, byte[] output, int offset, int len) throws IOException{
int bytesRead = 0;
while(bytesRead > -1 && bytesRead < len){
bytesRead += stream.read(start+bytesRead, output, offset + bytesRead, len-bytesRead);
}
}
private static void checkMagicBytes(FileStatus status, byte[] data, int offset) throws IOException {
for(int i =0, v = offset; i < MAGIC_LENGTH; i++, v++){
if(ParquetFileWriter.MAGIC[i] != data[v]){
byte[] magic = ArrayUtils.subarray(data, offset, offset + MAGIC_LENGTH);
throw new IOException(status.getPath() + " is not a Parquet file. expected magic number at tail " + Arrays.toString(ParquetFileWriter.MAGIC) + " but found " + Arrays.toString(magic));
}
}
}
public static List<Footer> getFooters(final Configuration conf, List<FileStatus> statuses, int parallelism) throws IOException {
final List<TimedRunnable<Footer>> readers = Lists.newArrayList();
List<Footer> foundFooters = Lists.newArrayList();
for(FileStatus status : statuses){
if(status.isDirectory()){
// first we check for summary file.
FileSystem fs = status.getPath().getFileSystem(conf);
final Path summaryPath = new Path(status.getPath(), ParquetFileWriter.PARQUET_METADATA_FILE);
if (fs.exists(summaryPath)){
FileStatus summaryStatus = fs.getFileStatus(summaryPath);
foundFooters.addAll(ParquetFileReader.readSummaryFile(conf, summaryStatus));
continue;
}
// else we handle as normal file.
for(FileStatus inStatus : fs.listStatus(status.getPath(), new DrillPathFilter())){
readers.add(new FooterReader(conf, inStatus));
}
}else{
readers.add(new FooterReader(conf, status));
}
}
if(!readers.isEmpty()){
foundFooters.addAll(TimedRunnable.run("Fetch Parquet Footers", logger, readers, parallelism));
}
return foundFooters;
}
private static class FooterReader extends TimedRunnable<Footer>{
final Configuration conf;
final FileStatus status;
public FooterReader(Configuration conf, FileStatus status) {
super();
this.conf = conf;
this.status = status;
}
@Override
protected Footer runInner() throws Exception {
return readFooter(conf, status);
}
@Override
protected IOException convertToIOException(Exception e) {
return new IOException("Failure while trying to get footer for file " + status.getPath(), e);
}
}
/**
* An updated footer reader that tries to read the entire footer without knowing the length.
* This should reduce the amount of seek/read roundtrips in most workloads.
* @param fs
* @param status
* @return
* @throws IOException
*/
public static Footer readFooter(final Configuration config, final FileStatus status) throws IOException {
final FileSystem fs = status.getPath().getFileSystem(config);
try(FSDataInputStream file = fs.open(status.getPath())) {
final long fileLength = status.getLen();
Preconditions.checkArgument(fileLength >= MIN_FILE_SIZE, "%s is not a Parquet file (too small)", status.getPath());
int len = (int) Math.min( fileLength, (long) DEFAULT_READ_SIZE);
byte[] footerBytes = new byte[len];
readFully(file, fileLength - len, footerBytes, 0, len);
checkMagicBytes(status, footerBytes, footerBytes.length - ParquetFileWriter.MAGIC.length);
final int size = BytesUtils.readIntLittleEndian(footerBytes, footerBytes.length - FOOTER_METADATA_SIZE);
if(size > footerBytes.length - FOOTER_METADATA_SIZE){
// if the footer is larger than our initial read, we need to read the rest.
byte[] origFooterBytes = footerBytes;
int origFooterRead = origFooterBytes.length - FOOTER_METADATA_SIZE;
footerBytes = new byte[size];
readFully(file, fileLength - size - FOOTER_METADATA_SIZE, footerBytes, 0, size - origFooterRead);
System.arraycopy(origFooterBytes, 0, footerBytes, size - origFooterRead, origFooterRead);
}else{
int start = footerBytes.length - (size + FOOTER_METADATA_SIZE);
footerBytes = ArrayUtils.subarray(footerBytes, start, start + size);
}
ParquetMetadata metadata = ParquetFormatPlugin.parquetMetadataConverter.readParquetMetadata(new ByteArrayInputStream(footerBytes));
Footer footer = new Footer(status.getPath(), metadata);
return footer;
}
}
}