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SplittableProcessElementInvoker.java
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SplittableProcessElementInvoker.java
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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.beam.runners.core;
import static com.google.common.base.Preconditions.checkNotNull;
import javax.annotation.Nullable;
import org.apache.beam.sdk.transforms.DoFn;
import org.apache.beam.sdk.transforms.reflect.DoFnInvoker;
import org.apache.beam.sdk.transforms.splittabledofn.RestrictionTracker;
import org.apache.beam.sdk.util.WindowedValue;
import org.joda.time.Instant;
/**
* A runner-specific hook for invoking a {@link DoFn.ProcessElement} method for a splittable {@link
* DoFn}, in particular, allowing the runner to access the {@link RestrictionTracker}.
*/
public abstract class SplittableProcessElementInvoker<
InputT, OutputT, RestrictionT, TrackerT extends RestrictionTracker<RestrictionT>> {
/** Specifies how to resume a splittable {@link DoFn.ProcessElement} call. */
public class Result {
@Nullable
private final RestrictionT residualRestriction;
private final DoFn.ProcessContinuation continuation;
private final @Nullable Instant futureOutputWatermark;
public Result(
@Nullable RestrictionT residualRestriction,
DoFn.ProcessContinuation continuation,
@Nullable Instant futureOutputWatermark) {
this.continuation = checkNotNull(continuation);
if (continuation.shouldResume()) {
checkNotNull(residualRestriction);
}
this.residualRestriction = residualRestriction;
this.futureOutputWatermark = futureOutputWatermark;
}
/**
* Can be {@code null} only if {@link #getContinuation} specifies the call should not resume.
* However, the converse is not true: this can be non-null even if {@link #getContinuation}
* is {@link DoFn.ProcessContinuation#stop()}.
*/
@Nullable
public RestrictionT getResidualRestriction() {
return residualRestriction;
}
public DoFn.ProcessContinuation getContinuation() {
return continuation;
}
public @Nullable Instant getFutureOutputWatermark() {
return futureOutputWatermark;
}
}
/**
* Invokes the {@link DoFn.ProcessElement} method using the given {@link DoFnInvoker} for the
* original {@link DoFn}, on the given element and with the given {@link RestrictionTracker}.
*
* @return Information on how to resume the call: residual restriction, a {@link
* DoFn.ProcessContinuation}, and a future output watermark.
*/
public abstract Result invokeProcessElement(
DoFnInvoker<InputT, OutputT> invoker, WindowedValue<InputT> element, TrackerT tracker);
}