org.apache.flink.table.runtime.functions.ProcessFunction Maven / Gradle / Ivy
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* 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.table.runtime.functions;
import org.apache.flink.api.common.functions.Function;
import org.apache.flink.api.common.functions.RuntimeContext;
import org.apache.flink.streaming.api.TimeDomain;
import org.apache.flink.streaming.api.TimerService;
import org.apache.flink.util.Collector;
/**
* A function that processes elements of a stream.
*
* For every element in the input stream {@link #processElement(Object, Context, Collector)}
* is invoked. This can produce zero or more elements as output. Implementations can also
* query the time and set timers through the provided {@link Context}. For firing timers
* {@link #onTimer(long, OnTimerContext, Collector)} will be invoked. This can again produce
* zero or more elements as output and register further timers.
*
*
NOTE: Access to keyed state and timers (which are also scoped to a key) is only
* available if the {@code ProcessFunction} is applied on a {@code KeyedStream}.
*
* @param Type of the input elements.
* @param Type of the output elements.
*/
public abstract class ProcessFunction implements Function {
private static final long serialVersionUID = 1L;
protected transient ExecutionContext executionContext;
public void open(ExecutionContext ctx) throws Exception {
this.executionContext = ctx;
}
public void close() throws Exception {}
public void endInput(Collector out) throws Exception {}
protected RuntimeContext getRuntimeContext() {
if (this.executionContext != null) {
return this.executionContext.getRuntimeContext();
} else {
throw new IllegalStateException("The stream exec runtime context has not been initialized.");
}
}
/**
* Process one element from the input stream.
*
* This function can output zero or more elements using the {@link Collector} parameter
* and also update internal state or set timers using the {@link Context} parameter.
*
* @param input The input value.
* @param ctx A {@link Context} that allows querying the timestamp of the element and getting
* a {@link TimerService} for registering timers and querying the time. The
* context is only valid during the invocation of this method, do not store it.
* @param out The collector for returning result values.
*
* @throws Exception This method may throw exceptions. Throwing an exception will cause the operation
* to fail and may trigger recovery.
*/
public abstract void processElement(I input, Context ctx, Collector out) throws Exception;
/**
* Called when a timer set using {@link TimerService} fires.
*
* @param timestamp The timestamp of the firing timer.
* @param ctx An {@link OnTimerContext} that allows querying the timestamp of the firing timer,
* querying the {@link TimeDomain} of the firing timer and getting a
* {@link TimerService} for registering timers and querying the time.
* The context is only valid during the invocation of this method, do not store it.
* @param out The collector for returning result values.
*
* @throws Exception This method may throw exceptions. Throwing an exception will cause the operation
* to fail and may trigger recovery.
*/
public void onTimer(long timestamp, OnTimerContext ctx, Collector out) throws Exception {}
/**
* Information available in an invocation of {@link #processElement(Object, Context, Collector)}
* or {@link #onTimer(long, OnTimerContext, Collector)}.
*/
public abstract static class Context {
/**
* A {@link TimerService} for querying time and registering timers.
*/
public abstract TimerService timerService();
}
/**
* Information available in an invocation of {@link #onTimer(long, OnTimerContext, Collector)}.
*/
public abstract static class OnTimerContext extends Context {
/**
* The {@link TimeDomain} of the firing timer.
*/
public abstract TimeDomain timeDomain();
}
}