com.datatorrent.api.StreamingApplication Maven / Gradle / Ivy
/**
* 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.
*
* 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.
* Application launchers (CLI) use the interface to identify application DAGs
* within jar files and supply the configuration upon instantiation.
*
* 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
}
/**
*
populateDAG.
*/
void populateDAG(DAG dag, Configuration conf);
}