| /* |
| * 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.samza.system; |
| |
| import java.util.ArrayDeque; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Map; |
| import java.util.NoSuchElementException; |
| import java.util.Queue; |
| import java.util.Set; |
| import org.apache.samza.SamzaException; |
| |
| /** |
| * Iterates over messages in the provided changelog {@link SystemStreamPartition} using the provided |
| * {@link SystemConsumer} until all messages have been consumed. |
| * |
| * The iterator has a {@link Mode} that depends on its position in the changelog SSP. If trim mode |
| * is enabled, the mode switches to {@code TRIM} if the current message offset is greater than the |
| * provided {@code endOffset}, or if {@code endOffset} is null. |
| * |
| * The iterator mode is used during transactional state restore to determine which changelog SSP entries |
| * should be restored and which ones need to be reverted / trimmed from the changelog topic. |
| */ |
| public class ChangelogSSPIterator { |
| public enum Mode { |
| RESTORE, |
| TRIM |
| } |
| |
| private final SystemConsumer systemConsumer; |
| private final String endOffset; |
| private final SystemAdmin admin; |
| private final Set<SystemStreamPartition> fetchSet; |
| private final boolean trimEnabled; |
| private Queue<IncomingMessageEnvelope> peeks; |
| private Mode mode = Mode.RESTORE; |
| |
| // endOffset is inclusive when restoring. endOffset == null means trim from staring offset to head. |
| public ChangelogSSPIterator(SystemConsumer systemConsumer, |
| SystemStreamPartition systemStreamPartition, String endOffset, SystemAdmin admin, boolean trimEnabled) { |
| this.systemConsumer = systemConsumer; |
| this.endOffset = endOffset; |
| this.trimEnabled = trimEnabled; |
| if (this.trimEnabled && endOffset == null) { |
| mode = Mode.TRIM; |
| } |
| this.admin = admin; |
| this.fetchSet = new HashSet<>(); |
| this.fetchSet.add(systemStreamPartition); |
| this.peeks = new ArrayDeque<>(); |
| } |
| |
| public boolean hasNext() { |
| refresh(); |
| |
| return peeks.size() > 0; |
| } |
| |
| public IncomingMessageEnvelope next() { |
| refresh(); |
| |
| if (peeks.size() == 0) { |
| throw new NoSuchElementException(); |
| } |
| |
| IncomingMessageEnvelope envelope = peeks.poll(); |
| |
| // if trimming changelog is enabled, then switch to trim mode if if we've consumed past the end offset |
| // (i.e., endOffset was null or current offset is > endOffset) |
| if (this.trimEnabled && (endOffset == null || admin.offsetComparator(envelope.getOffset(), endOffset) > 0)) { |
| mode = Mode.TRIM; |
| } |
| |
| return envelope; |
| } |
| |
| public Mode getMode() { |
| return this.mode; |
| } |
| |
| private void refresh() { |
| if (peeks.size() == 0) { |
| try { |
| Map<SystemStreamPartition, List<IncomingMessageEnvelope>> envelopes = systemConsumer.poll(fetchSet, SystemConsumer.BLOCK_ON_OUTSTANDING_MESSAGES); |
| |
| for (List<IncomingMessageEnvelope> systemStreamPartitionEnvelopes : envelopes.values()) { |
| peeks.addAll(systemStreamPartitionEnvelopes); |
| } |
| } catch (InterruptedException e) { |
| Thread.currentThread().interrupt(); |
| throw new SamzaException(e); |
| } |
| } |
| } |
| } |