| /** |
| * 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 com.datatorrent.api; |
| |
| import org.apache.hadoop.conf.Configuration; |
| |
| /** |
| * Interface to be implemented for Java based streaming application declaration. |
| * <p> |
| * An application is the top level DAG with external configuration for |
| * application master / engine settings, application specific properties or |
| * overrides for individual operators in the DAG. <br> |
| * Application launchers (CLI) use the interface to identify application DAGs |
| * within jar files and supply the configuration upon instantiation. |
| * <p> |
| * Operator properties in the DAG can be configured externally. When an |
| * application is launched from the CLI, any settings in dt-site.xml would |
| * override property values in the DAG. It is therefore possible to have |
| * defaults in the DAG code and supply environment/launch context specific |
| * settings through the configuration. |
| * |
| * @since 0.3.2 |
| */ |
| public interface StreamingApplication |
| { |
| /** |
| * Prefix used in configuration keys. |
| */ |
| String APEX_PREFIX = "apex."; |
| |
| /** |
| * Legacy prefix, to be removed in future release, |
| * when all code dependencies are upgraded. |
| */ |
| @Deprecated |
| String DT_PREFIX = "dt."; |
| /** |
| * Launch mode for the application. |
| * Used in the client to set configuration depending on how the DAG is executed. |
| */ |
| String ENVIRONMENT = DT_PREFIX + "environment"; |
| |
| /** |
| * Streaming Application code would be executing in one of these environments. |
| * ENVIRONMENT key in conf is set to LOCAL when the application is running in local mode. |
| * It's set to CLUSTER when the application is running in distributed mode. |
| */ |
| enum Environment |
| { |
| LOCAL, |
| CLUSTER |
| } |
| |
| /** |
| * <p>populateDAG.</p> |
| */ |
| void populateDAG(DAG dag, Configuration conf); |
| |
| } |