| /* |
| * 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.accumulo.core.client.impl; |
| |
| import java.util.Collections; |
| import java.util.Iterator; |
| import java.util.List; |
| import java.util.Map.Entry; |
| import java.util.NoSuchElementException; |
| import java.util.concurrent.ArrayBlockingQueue; |
| import java.util.concurrent.SynchronousQueue; |
| import java.util.concurrent.ThreadPoolExecutor; |
| import java.util.concurrent.TimeUnit; |
| |
| import org.apache.accumulo.core.client.AccumuloException; |
| import org.apache.accumulo.core.client.AccumuloSecurityException; |
| import org.apache.accumulo.core.client.SampleNotPresentException; |
| import org.apache.accumulo.core.client.TableDeletedException; |
| import org.apache.accumulo.core.client.TableNotFoundException; |
| import org.apache.accumulo.core.client.TableOfflineException; |
| import org.apache.accumulo.core.client.impl.ThriftScanner.ScanState; |
| import org.apache.accumulo.core.client.impl.ThriftScanner.ScanTimedOutException; |
| import org.apache.accumulo.core.data.Key; |
| import org.apache.accumulo.core.data.KeyValue; |
| import org.apache.accumulo.core.data.Range; |
| import org.apache.accumulo.core.data.Value; |
| import org.apache.accumulo.core.security.Authorizations; |
| import org.apache.accumulo.core.util.NamingThreadFactory; |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| public class ScannerIterator implements Iterator<Entry<Key,Value>> { |
| |
| private static final Logger log = LoggerFactory.getLogger(ScannerIterator.class); |
| |
| // scanner options |
| private int timeOut; |
| |
| // scanner state |
| private Iterator<KeyValue> iter; |
| private ScanState scanState; |
| |
| private ScannerOptions options; |
| |
| private ArrayBlockingQueue<Object> synchQ; |
| |
| private boolean finished = false; |
| |
| private boolean readaheadInProgress = false; |
| private long batchCount = 0; |
| private long readaheadThreshold; |
| |
| private static final List<KeyValue> EMPTY_LIST = Collections.emptyList(); |
| |
| private static ThreadPoolExecutor readaheadPool = new ThreadPoolExecutor(0, Integer.MAX_VALUE, 3l, TimeUnit.SECONDS, new SynchronousQueue<Runnable>(), |
| new NamingThreadFactory("Accumulo scanner read ahead thread")); |
| |
| private class Reader implements Runnable { |
| |
| @Override |
| public void run() { |
| |
| try { |
| while (true) { |
| List<KeyValue> currentBatch = ThriftScanner.scan(scanState.context, scanState, timeOut); |
| |
| if (currentBatch == null) { |
| synchQ.add(EMPTY_LIST); |
| return; |
| } |
| |
| if (currentBatch.size() == 0) |
| continue; |
| |
| synchQ.add(currentBatch); |
| return; |
| } |
| } catch (IsolationException | ScanTimedOutException | AccumuloException | AccumuloSecurityException | TableDeletedException | TableOfflineException |
| | SampleNotPresentException e) { |
| log.trace("{}", e.getMessage(), e); |
| synchQ.add(e); |
| } catch (TableNotFoundException e) { |
| log.warn("{}", e.getMessage(), e); |
| synchQ.add(e); |
| } catch (Exception e) { |
| log.error("{}", e.getMessage(), e); |
| synchQ.add(e); |
| } |
| } |
| |
| } |
| |
| ScannerIterator(ClientContext context, String tableId, Authorizations authorizations, Range range, int size, int timeOut, ScannerOptions options, |
| boolean isolated, long readaheadThreshold) { |
| this.timeOut = timeOut; |
| this.readaheadThreshold = readaheadThreshold; |
| |
| this.options = new ScannerOptions(options); |
| |
| synchQ = new ArrayBlockingQueue<>(1); |
| |
| if (this.options.fetchedColumns.size() > 0) { |
| range = range.bound(this.options.fetchedColumns.first(), this.options.fetchedColumns.last()); |
| } |
| |
| scanState = new ScanState(context, tableId, authorizations, new Range(range), options.fetchedColumns, size, options.serverSideIteratorList, |
| options.serverSideIteratorOptions, isolated, readaheadThreshold, options.getSamplerConfiguration(), options.batchTimeOut, options.classLoaderContext); |
| |
| // If we want to start readahead immediately, don't wait for hasNext to be called |
| if (0l == readaheadThreshold) { |
| initiateReadAhead(); |
| } |
| iter = null; |
| } |
| |
| private void initiateReadAhead() { |
| readaheadInProgress = true; |
| readaheadPool.execute(new Reader()); |
| } |
| |
| @Override |
| @SuppressWarnings("unchecked") |
| public boolean hasNext() { |
| if (finished) |
| return false; |
| |
| if (iter != null && iter.hasNext()) { |
| return true; |
| } |
| |
| // this is done in order to find see if there is another batch to get |
| |
| try { |
| if (!readaheadInProgress) { |
| // no read ahead run, fetch the next batch right now |
| new Reader().run(); |
| } |
| |
| Object obj = synchQ.take(); |
| |
| if (obj instanceof Exception) { |
| finished = true; |
| if (obj instanceof RuntimeException) |
| throw (RuntimeException) obj; |
| else |
| throw new RuntimeException((Exception) obj); |
| } |
| |
| List<KeyValue> currentBatch = (List<KeyValue>) obj; |
| |
| if (currentBatch.size() == 0) { |
| currentBatch = null; |
| finished = true; |
| return false; |
| } |
| iter = currentBatch.iterator(); |
| batchCount++; |
| |
| if (batchCount > readaheadThreshold) { |
| // start a thread to read the next batch |
| initiateReadAhead(); |
| } |
| |
| } catch (InterruptedException e1) { |
| throw new RuntimeException(e1); |
| } |
| |
| return true; |
| } |
| |
| @Override |
| public Entry<Key,Value> next() { |
| if (hasNext()) |
| return iter.next(); |
| throw new NoSuchElementException(); |
| } |
| |
| // just here to satisfy the interface |
| // could make this actually delete things from the database |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException("remove is not supported in Scanner"); |
| } |
| |
| } |