org.apache.flink.streaming.api.windowing.assigners.WindowAssigner 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.flink.streaming.api.windowing.assigners;
import org.apache.flink.annotation.PublicEvolving;
import org.apache.flink.api.common.ExecutionConfig;
import org.apache.flink.api.common.typeutils.TypeSerializer;
import org.apache.flink.streaming.api.environment.StreamExecutionEnvironment;
import org.apache.flink.streaming.api.windowing.triggers.Trigger;
import org.apache.flink.streaming.api.windowing.windows.Window;
import java.io.Serializable;
import java.util.Collection;
/**
* A {@code WindowAssigner} assigns zero or more {@link Window Windows} to an element.
*
* In a window operation, elements are grouped by their key (if available) and by the windows to
* which it was assigned. The set of elements with the same key and window is called a pane.
* When a {@link Trigger} decides that a certain pane should fire the
* {@link org.apache.flink.streaming.api.functions.windowing.WindowFunction} is applied
* to produce output elements for that pane.
*
* @param The type of elements that this WindowAssigner can assign windows to.
* @param The type of {@code Window} that this assigner assigns.
*/
@PublicEvolving
public abstract class WindowAssigner implements Serializable {
private static final long serialVersionUID = 1L;
/**
* Returns a {@code Collection} of windows that should be assigned to the element.
*
* @param element The element to which windows should be assigned.
* @param timestamp The timestamp of the element.
* @param context The {@link WindowAssignerContext} in which the assigner operates.
*/
public abstract Collection assignWindows(T element, long timestamp, WindowAssignerContext context);
/**
* Returns the default trigger associated with this {@code WindowAssigner}.
*/
public abstract Trigger getDefaultTrigger(StreamExecutionEnvironment env);
/**
* Returns a {@link TypeSerializer} for serializing windows that are assigned by
* this {@code WindowAssigner}.
*/
public abstract TypeSerializer getWindowSerializer(ExecutionConfig executionConfig);
/**
* Returns {@code true} if elements are assigned to windows based on event time,
* {@code false} otherwise.
*/
public abstract boolean isEventTime();
/**
* A context provided to the {@link WindowAssigner} that allows it to query the
* current processing time.
*
* This is provided to the assigner by its containing
* {@link org.apache.flink.streaming.runtime.operators.windowing.WindowOperator},
* which, in turn, gets it from the containing
* {@link org.apache.flink.streaming.runtime.tasks.StreamTask}.
*/
public abstract static class WindowAssignerContext {
/**
* Returns the current processing time.
*/
public abstract long getCurrentProcessingTime();
}
}