/*
* 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.nifi.provenance.store.iterator;
import java.io.EOFException;
import java.io.File;
import java.io.FileNotFoundException;
import java.io.IOException;
import java.util.Collections;
import java.util.Iterator;
import java.util.List;
import java.util.Optional;
import org.apache.nifi.provenance.ProvenanceEventRecord;
import org.apache.nifi.provenance.serialization.RecordReader;
import org.apache.nifi.provenance.store.RecordReaderFactory;
public class SequentialRecordReaderEventIterator implements EventIterator {
private final Iterator<File> fileIterator;
private final RecordReaderFactory readerFactory;
private final long minimumEventId;
private final int maxAttributeChars;
private boolean closed = false;
private RecordReader reader;
public SequentialRecordReaderEventIterator(final List<File> filesToRead, final RecordReaderFactory readerFactory, final long minimumEventId, final int maxAttributeChars) {
this.fileIterator = filesToRead.iterator();
this.readerFactory = readerFactory;
this.minimumEventId = minimumEventId;
this.maxAttributeChars = maxAttributeChars;
}
@Override
public void close() throws IOException {
closed = true;
if (reader != null) {
reader.close();
}
}
@Override
public Optional<ProvenanceEventRecord> nextEvent() throws IOException {
if (closed) {
throw new IOException("EventIterator is already closed");
}
if (reader == null) {
if (!rotateReader()) {
return Optional.empty();
}
}
while (true) {
final ProvenanceEventRecord event = reader.nextRecord();
if (event == null) {
if (rotateReader()) {
continue;
} else {
return Optional.empty();
}
} else {
return Optional.of(event);
}
}
}
private boolean rotateReader() throws IOException {
final boolean readerExists = (reader != null);
if (readerExists) {
reader.close();
}
boolean multipleReadersOpened = false;
while (true) {
if (!fileIterator.hasNext()) {
return false;
}
final File eventFile = fileIterator.next();
try {
reader = readerFactory.newRecordReader(eventFile, Collections.emptyList(), maxAttributeChars);
break;
} catch (final FileNotFoundException | EOFException e) {
multipleReadersOpened = true;
// File may have aged off or was not fully written. Move to next file
continue;
}
}
// If this is the first file in our list, the event of interest may not be the first event,
// so skip to the event that we want.
if (!readerExists && !multipleReadersOpened) {
reader.skipToEvent(minimumEventId);
}
return true;
}
}