| /** |
| * 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 |
| * <p> |
| * http://www.apache.org/licenses/LICENSE-2.0 |
| * <p> |
| * 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.storm.state; |
| |
| import java.util.AbstractMap; |
| import java.util.Iterator; |
| import java.util.Map; |
| import java.util.NoSuchElementException; |
| import java.util.Set; |
| import org.apache.storm.shade.com.google.common.collect.Iterators; |
| import org.apache.storm.shade.com.google.common.collect.PeekingIterator; |
| |
| /** |
| * Base implementation of iterator over {@link KeyValueState}. Encoded/Decoded types of key and value are all generic. |
| */ |
| public abstract class BaseStateIterator<K, V, KENCODEDT, VENCODEDT> implements Iterator<Map.Entry<K, V>> { |
| |
| private final PeekingIterator<Map.Entry<KENCODEDT, VENCODEDT>> pendingPrepareIterator; |
| private final PeekingIterator<Map.Entry<KENCODEDT, VENCODEDT>> pendingCommitIterator; |
| private final Set<KENCODEDT> providedKeys; |
| |
| private boolean firstLoad = true; |
| private PeekingIterator<Map.Entry<KENCODEDT, VENCODEDT>> pendingIterator; |
| private PeekingIterator<Map.Entry<KENCODEDT, VENCODEDT>> cachedResultIterator; |
| |
| /** |
| * Constructor. |
| * |
| * @param pendingPrepareIterator The iterator of pendingPrepare |
| * @param pendingCommitIterator The iterator of pendingCommit |
| * @param initialProvidedKeys The initial value of provided keys |
| */ |
| public BaseStateIterator(Iterator<Map.Entry<KENCODEDT, VENCODEDT>> pendingPrepareIterator, |
| Iterator<Map.Entry<KENCODEDT, VENCODEDT>> pendingCommitIterator, |
| Set<KENCODEDT> initialProvidedKeys) { |
| this.pendingPrepareIterator = Iterators.peekingIterator(pendingPrepareIterator); |
| this.pendingCommitIterator = Iterators.peekingIterator(pendingCommitIterator); |
| this.providedKeys = initialProvidedKeys; |
| } |
| |
| @Override |
| public boolean hasNext() { |
| if (seekToAvailableEntry(pendingPrepareIterator)) { |
| pendingIterator = pendingPrepareIterator; |
| return true; |
| } |
| |
| if (seekToAvailableEntry(pendingCommitIterator)) { |
| pendingIterator = pendingCommitIterator; |
| return true; |
| } |
| |
| |
| if (firstLoad) { |
| // load the first part of entries |
| fillCachedResultIterator(); |
| firstLoad = false; |
| } |
| |
| while (true) { |
| if (seekToAvailableEntry(cachedResultIterator)) { |
| pendingIterator = cachedResultIterator; |
| return true; |
| } |
| |
| if (isEndOfDataFromStorage()) { |
| break; |
| } |
| |
| fillCachedResultIterator(); |
| } |
| |
| pendingIterator = null; |
| return false; |
| } |
| |
| private void fillCachedResultIterator() { |
| Iterator<Map.Entry<KENCODEDT, VENCODEDT>> iterator = loadChunkFromStateStorage(); |
| if (iterator != null) { |
| cachedResultIterator = Iterators.peekingIterator(iterator); |
| } else { |
| cachedResultIterator = null; |
| } |
| } |
| |
| @Override |
| public Map.Entry<K, V> next() { |
| if (!hasNext()) { |
| throw new NoSuchElementException(); |
| } |
| |
| Map.Entry<KENCODEDT, VENCODEDT> keyValue = pendingIterator.next(); |
| |
| K key = decodeKey(keyValue.getKey()); |
| V value = decodeValue(keyValue.getValue()); |
| |
| providedKeys.add(keyValue.getKey()); |
| return new AbstractMap.SimpleEntry(key, value); |
| } |
| |
| @Override |
| public void remove() { |
| throw new UnsupportedOperationException(); |
| } |
| |
| /** |
| * Load some part of state KVs from storage and returns iterator of cached data from storage. |
| * |
| * @return Iterator of loaded state KVs |
| */ |
| protected abstract Iterator<Map.Entry<KENCODEDT, VENCODEDT>> loadChunkFromStateStorage(); |
| |
| /** |
| * Check whether end of data is reached from storage state KVs. |
| * |
| * @return whether end of data is reached from storage state KVs |
| */ |
| protected abstract boolean isEndOfDataFromStorage(); |
| |
| /** |
| * Decode key to convert encoded type of key to state key type. |
| * |
| * @param key raw type of encoded key |
| * @return Decoded value of key |
| */ |
| protected abstract K decodeKey(KENCODEDT key); |
| |
| /** |
| * Decode value to convert encoded type of value to state value type. |
| * |
| * @param value raw type of encoded value |
| * @return Decoded value of value |
| */ |
| protected abstract V decodeValue(VENCODEDT value); |
| |
| /** |
| * Check whether the value is tombstone (deletion mark) value. |
| * |
| * @param value the value to check |
| * @return true if the value is tombstone, false otherwise |
| */ |
| protected abstract boolean isTombstoneValue(VENCODEDT value); |
| |
| private boolean seekToAvailableEntry(PeekingIterator<Map.Entry<KENCODEDT, VENCODEDT>> iterator) { |
| if (iterator != null) { |
| while (iterator.hasNext()) { |
| Map.Entry<KENCODEDT, VENCODEDT> entry = iterator.peek(); |
| if (!providedKeys.contains(entry.getKey())) { |
| if (isTombstoneValue(entry.getValue())) { |
| providedKeys.add(entry.getKey()); |
| } else { |
| return true; |
| } |
| } |
| |
| iterator.next(); |
| } |
| } |
| |
| return false; |
| } |
| |
| } |