cryptoe commented on code in PR #15007: URL: https://github.com/apache/druid/pull/15007#discussion_r1341599830
########## extensions-core/multi-stage-query/src/main/java/org/apache/druid/msq/querykit/ChainedProcessorManager.java: ########## @@ -0,0 +1,104 @@ +/* + * 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.druid.msq.querykit; + +import com.google.common.base.Preconditions; +import com.google.common.util.concurrent.Futures; +import com.google.common.util.concurrent.ListenableFuture; +import com.google.common.util.concurrent.SettableFuture; +import org.apache.druid.common.guava.FutureUtils; +import org.apache.druid.frame.processor.FrameProcessor; +import org.apache.druid.frame.processor.manager.ProcessorAndCallback; +import org.apache.druid.frame.processor.manager.ProcessorManager; +import org.apache.druid.utils.CloseableUtils; + +import javax.annotation.Nullable; +import java.util.Optional; +import java.util.function.Function; + +/** + * Manager that chains processors: runs {@link #first} first, then based on its result, creates {@link #restFuture} + * using {@link #restFactory} and runs that next. + */ +public class ChainedProcessorManager<A, B, R> implements ProcessorManager<Object, R> +{ + /** + * First processor. This one blocks all the others. The reference is set to null once the processor has been + * returned by the channel. + */ + @Nullable + private FrameProcessor<A> first; + + /** + * Produces {@link #restFuture}. + */ + private final Function<A, ProcessorManager<B, R>> restFactory; + + /** + * The rest of the processors. Produced by {@link #restFactory} once {@link #first} has completed. + */ + private final SettableFuture<ProcessorManager<B, R>> restFuture = SettableFuture.create(); + + public ChainedProcessorManager( + final FrameProcessor<A> first, + final Function<A, ProcessorManager<B, R>> restFactory + ) + { + this.first = Preconditions.checkNotNull(first, "first"); + this.restFactory = Preconditions.checkNotNull(restFactory, "restFactory"); + } + + @Override + public ListenableFuture<Optional<ProcessorAndCallback<Object>>> next() + { + if (first != null) { + //noinspection unchecked + final FrameProcessor<Object> tmp = (FrameProcessor<Object>) first; + first = null; + return Futures.immediateFuture(Optional.of(new ProcessorAndCallback<>(tmp, this::onFirstProcessorComplete))); + } else { + return FutureUtils.transformAsync( + restFuture, + rest -> (ListenableFuture) rest.next() + ); + } + } + + private void onFirstProcessorComplete(final Object firstResult) + { + //noinspection unchecked + restFuture.set(restFactory.apply((A) firstResult)); + } + + @Override + public R result() + { + return FutureUtils.getUncheckedImmediately(restFuture).result(); + } + + @Override + public void close() + { Review Comment: ``` CPM cpm=new CPM(); cpm.close(); cpm.next(); ``` -- This is an automated message from the Apache Git Service. To respond to the message, please log on to GitHub and use the URL above to go to the specific comment. To unsubscribe, e-mail: [email protected] For queries about this service, please contact Infrastructure at: [email protected] --------------------------------------------------------------------- To unsubscribe, e-mail: [email protected] For additional commands, e-mail: [email protected]
