| /* |
| * 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.fluo.api.observer; |
| |
| import org.apache.fluo.api.client.FluoClient; |
| import org.apache.fluo.api.client.TransactionBase; |
| import org.apache.fluo.api.config.SimpleConfiguration; |
| import org.apache.fluo.api.data.Bytes; |
| import org.apache.fluo.api.data.Column; |
| import org.apache.fluo.api.metrics.MetricsReporter; |
| |
| /** |
| * Implemented by users to a watch a {@link Column} and be notified of changes to the Column via the |
| * {@link #process(TransactionBase, Bytes, Column)} method. An observer is created for each worker |
| * thread and reused for the lifetime of a worker thread. Consider extending |
| * {@link AbstractObserver} as it will let you optionally implement {@link #init(Context)} and |
| * {@link #close()}. The abstract class will also shield you from the addition of interface methods. |
| * |
| * @since 1.0.0 |
| */ |
| public interface Observer { |
| |
| /** |
| * @since 1.0.0 |
| */ |
| enum NotificationType { |
| WEAK, STRONG |
| } |
| |
| /** |
| * A {@link Column} and {@link NotificationType} pair |
| * |
| * @since 1.0.0 |
| */ |
| class ObservedColumn { |
| private final Column col; |
| private final NotificationType notificationType; |
| |
| public ObservedColumn(Column col, NotificationType notificationType) { |
| this.col = col; |
| this.notificationType = notificationType; |
| } |
| |
| public Column getColumn() { |
| return col; |
| } |
| |
| public NotificationType getType() { |
| return notificationType; |
| } |
| } |
| |
| /** |
| * @since 1.0.0 |
| */ |
| interface Context { |
| /** |
| * @return A configuration object with application configuration like that returned by |
| * {@link FluoClient#getAppConfiguration()} |
| */ |
| SimpleConfiguration getAppConfiguration(); |
| |
| /** |
| * @return The per observer configuration that's specific to this observer. |
| */ |
| SimpleConfiguration getObserverConfiguration(); |
| |
| /** |
| * @return A {@link MetricsReporter} to report application metrics from this observer |
| */ |
| MetricsReporter getMetricsReporter(); |
| } |
| |
| /** |
| * Implemented by user to initialize Observer. |
| * |
| * @param context Observer context |
| */ |
| void init(Context context) throws Exception; |
| |
| /** |
| * Implemented by users to process notifications on a {@link ObservedColumn}. If a notification |
| * occurs, this method passes the user a {@link TransactionBase} as well as the row and |
| * {@link Column} where the notification occurred. The user can use the {@link TransactionBase} to |
| * read and write to Fluo. After this method returns, {@link TransactionBase} will be committed |
| * and closed by Fluo. |
| */ |
| void process(TransactionBase tx, Bytes row, Column col) throws Exception; |
| |
| /** |
| * Implemented by user to return an {@link ObservedColumn} that will trigger this observer. During |
| * initialization, this information is stored in zookeeper so that workers have a consistent view. |
| * If a worker loads an Observer and the information returned differs from what is in zookeeper |
| * then an exception will be thrown. It is safe to assume that {@link #init(Context)} will be |
| * called before this method. If the return value of the method is derived from what is passed to |
| * {@link #init(Context)}, then the derivation process should be deterministic. |
| */ |
| ObservedColumn getObservedColumn(); |
| |
| /** |
| * Implemented by user to close resources used by Observer |
| */ |
| void close(); |
| } |