rkhachatryan commented on a change in pull request #15420: URL: https://github.com/apache/flink/pull/15420#discussion_r647758316
########## File path: flink-state-backends/flink-statebackend-changelog/src/main/java/org/apache/flink/state/changelog/restore/FunctionDelegationHelper.java ########## @@ -0,0 +1,145 @@ +/* + * 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.state.changelog.restore; + +import org.apache.flink.annotation.Internal; +import org.apache.flink.api.common.functions.AggregateFunction; +import org.apache.flink.api.common.functions.Function; +import org.apache.flink.api.common.functions.ReduceFunction; +import org.apache.flink.api.common.state.AggregatingStateDescriptor; +import org.apache.flink.api.common.state.ReducingStateDescriptor; +import org.apache.flink.api.common.state.State; +import org.apache.flink.api.common.state.StateDescriptor; + +import org.slf4j.Logger; +import org.slf4j.LoggerFactory; + +import javax.annotation.Nullable; + +import java.util.HashMap; +import java.util.Map; + +import static org.apache.flink.util.Preconditions.checkNotNull; +import static org.apache.flink.util.Preconditions.checkState; + +/** + * {@link DelegatingFunction Delegating functions} are used to create metadata on recovery when the + * actual function code is not known yet. Once the actual function is known, backend updates the + * delegate which starts receiving the calls. + */ +@SuppressWarnings({"unchecked", "rawtypes"}) +@Internal +public class FunctionDelegationHelper { + private static final Logger LOG = LoggerFactory.getLogger(FunctionDelegationHelper.class); + + public static <T> ReduceFunction<T> delegateReduceFunction() { + return new DelegatingReduceFunction<>(); + } + + public static <IN, ACC, OUT> AggregateFunction<IN, ACC, OUT> delegateAggregateFunction() { + return new DelegatingAggregateFunction<>(); + } + + private interface DelegatingFunction<F> extends Function { + void delegateIfNeeded(F delegated); + } + + private final Map<String, DelegatingFunction> delegatingFunctions = new HashMap<>(); + + public <T, S extends State, F> void addOrUpdate(StateDescriptor<S, T> stateDescriptor) { + F function = tryGetFunction(stateDescriptor); + String name = stateDescriptor.getName(); + if (function instanceof DelegatingFunction) { + LOG.debug("add delegate: {}", name); + delegatingFunctions.putIfAbsent(name, (DelegatingFunction<?>) function); + } else { + DelegatingFunction<F> delegating = delegatingFunctions.get(name); + if (delegating != null) { + LOG.debug("update delegate: {}", name); + checkState(function != null, "unable to extract function for state " + name); + delegating.delegateIfNeeded(function); + } + } + } + + @Nullable + private static <F extends Function> F tryGetFunction(StateDescriptor<?, ?> stateDescriptor) { + if (stateDescriptor instanceof ReducingStateDescriptor) { + return (F) ((ReducingStateDescriptor) stateDescriptor).getReduceFunction(); + } else if (stateDescriptor instanceof AggregatingStateDescriptor) { + return (F) ((AggregatingStateDescriptor) stateDescriptor).getAggregateFunction(); + } else { + return null; + } + } + + static class DelegatingAggregateFunction<IN, ACC, OUT> + implements AggregateFunction<IN, ACC, OUT>, + DelegatingFunction<AggregateFunction<IN, ACC, OUT>> { + @Nullable private AggregateFunction<IN, ACC, OUT> delegated; + + @Override + public void delegateIfNeeded(AggregateFunction<IN, ACC, OUT> delegated) { + if (this.delegated == null) { + this.delegated = checkNotNull(delegated); + } + } + + @Override + public ACC createAccumulator() { + checkNotNull(delegated); + return delegated.createAccumulator(); + } + + @Override + public ACC add(IN value, ACC accumulator) { + checkNotNull(delegated); + return delegated.add(value, accumulator); + } + + @Override + public OUT getResult(ACC accumulator) { + checkNotNull(delegated); + return delegated.getResult(accumulator); + } + + @Override + public ACC merge(ACC a, ACC b) { + checkNotNull(delegated); + return delegated.merge(a, b); + } + } + + static class DelegatingReduceFunction<T> Review comment: Good point, thanks! -- This is an automated message from the Apache Git Service. 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