org.apache.crunch.ReadableData 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 org.apache.crunch;
import org.apache.hadoop.conf.Configuration;
import org.apache.hadoop.mapreduce.TaskInputOutputContext;
import java.io.IOException;
import java.io.Serializable;
import java.util.Set;
/**
* Represents the contents of a data source that can be read on the cluster from within one
* of the tasks running as part of a Crunch pipeline.
*/
public interface ReadableData extends Serializable {
/**
* @return Any {@code SourceTarget} instances that must exist before the data in
* this instance can be read. Used by the planner in sequencing job processing.
*/
Set> getSourceTargets();
/**
* Allows this instance to specify any additional configuration settings that may
* be needed by the job that it is launched in.
*
* @param conf The {@code Configuration} object for the job
*/
void configure(Configuration conf);
/**
* Read the data referenced by this instance within the given context.
*
* @param context The context of the task that is reading the data
* @return An iterable reference to the data in this instance
* @throws IOException If the data cannot be read
*/
Iterable read(TaskInputOutputContext context) throws IOException;
}