| /** |
| * 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.apex.malhar.lib.db.cache; |
| |
| import java.io.IOException; |
| |
| import javax.validation.constraints.NotNull; |
| |
| import org.slf4j.Logger; |
| import org.slf4j.LoggerFactory; |
| |
| import org.apache.apex.malhar.lib.db.Connectable; |
| import org.apache.apex.malhar.lib.util.KeyValPair; |
| |
| import com.datatorrent.api.Context; |
| import com.datatorrent.api.DefaultInputPort; |
| import com.datatorrent.api.DefaultOutputPort; |
| import com.datatorrent.api.Operator; |
| |
| /** |
| * This is the base implementation of an operator that maintains a loading cache. |
| * The cache has a maximum size and its entries expire after a specified time. |
| * Subclasses should implement the method which extracts a cache key from a tuple. |
| * <p> |
| * Specifically concrete implementations of this class should provide:<br/> |
| * <ul> |
| * <li>{@link Connectable} that holds connection parameters and setup/teardown functionality.</li> |
| * <li>Method to extract a key from tuple.</li> |
| * <li>Query to fetch the value of the key from tuple when the value is not present in the cache.</li> |
| * </ul> |
| * </p> |
| * @displayName Abstract DB Lookup Cache Backed |
| * @category Input |
| * @tags cache, key value |
| * |
| * @param <T> type of tuples |
| * @param <S> type of store |
| * @since 0.9.1 |
| */ |
| public abstract class AbstractDBLookupCacheBackedOperator<T, S extends Connectable> |
| implements Operator, CacheManager.Backup |
| { |
| @NotNull |
| protected S store; |
| @NotNull |
| protected CacheManager cacheManager; |
| |
| protected AbstractDBLookupCacheBackedOperator() |
| { |
| cacheManager = new CacheManager(); |
| } |
| |
| /** |
| * The input port on which tuples are received. |
| */ |
| public final transient DefaultInputPort<T> input = new DefaultInputPort<T>() |
| { |
| @Override |
| public void process(T tuple) |
| { |
| processTuple(tuple); |
| } |
| }; |
| |
| protected void processTuple(T tuple) |
| { |
| Object key = getKeyFromTuple(tuple); |
| Object value = cacheManager.get(key); |
| |
| if (value != null) { |
| output.emit(new KeyValPair<>(key, value)); |
| } |
| } |
| |
| public final transient DefaultOutputPort<KeyValPair<Object, Object>> output = new DefaultOutputPort<>(); |
| |
| @Override |
| public void beginWindow(long l) |
| { |
| //Do nothing |
| } |
| |
| @Override |
| public void endWindow() |
| { |
| //Do nothing |
| } |
| |
| @Override |
| public void setup(Context.OperatorContext context) |
| { |
| cacheManager.setBackup(this); |
| try { |
| cacheManager.initialize(); |
| } catch (IOException e) { |
| throw new RuntimeException(e); |
| } |
| } |
| |
| @Override |
| public void teardown() |
| { |
| try { |
| cacheManager.close(); |
| } catch (IOException e) { |
| LOG.error("closing manager", e); |
| } |
| } |
| |
| @Override |
| public void connect() throws IOException |
| { |
| store.connect(); |
| } |
| |
| @Override |
| public boolean isConnected() |
| { |
| return store.isConnected(); |
| } |
| |
| @Override |
| public void disconnect() throws IOException |
| { |
| store.disconnect(); |
| } |
| |
| public void setStore(S store) |
| { |
| this.store = store; |
| } |
| |
| public S getStore() |
| { |
| return store; |
| } |
| |
| public void setCacheManager(CacheManager cacheManager) |
| { |
| this.cacheManager = cacheManager; |
| } |
| |
| public CacheManager getCacheManager() |
| { |
| return cacheManager; |
| } |
| |
| /** |
| * <br>This operator receives tuples which encapsulates the keys. Concrete classes should |
| * provide the implementation to extract a key from a tuple.</br> |
| * |
| * @param tuple input tuple to the operator. |
| * @return key corresponding to the operator. |
| */ |
| protected abstract Object getKeyFromTuple(T tuple); |
| |
| private static final Logger LOG = LoggerFactory.getLogger(AbstractDBLookupCacheBackedOperator.class); |
| |
| } |