[MNG-8031] Backport concurrent friendly transport listener (#1471)

Backport of simplex transfer listener.

---

https://issues.apache.org/jira/browse/MNG-8031

maven-embedder/src/main/java/org/apache/maven/cli/MavenCli.java

@@ -69,9 +69,7 @@
 import org.apache.maven.cli.logging.Slf4jConfigurationFactory;
 import org.apache.maven.cli.logging.Slf4jLoggerManager;
 import org.apache.maven.cli.logging.Slf4jStdoutLogger;
-import org.apache.maven.cli.transfer.ConsoleMavenTransferListener;
-import org.apache.maven.cli.transfer.QuietMavenTransferListener;
-import org.apache.maven.cli.transfer.Slf4jMavenTransferListener;
+import org.apache.maven.cli.transfer.*;
 import org.apache.maven.eventspy.internal.EventSpyDispatcher;
 import org.apache.maven.exception.DefaultExceptionHandler;
 import org.apache.maven.exception.ExceptionHandler;
@@ -1627,7 +1625,7 @@ static class IllegalUseOfUndefinedProperty extends IllegalArgumentException {
     //
 
     protected TransferListener getConsoleTransferListener(boolean printResourceNames) {
-        return new ConsoleMavenTransferListener(System.out, printResourceNames);
+        return new SimplexTransferListener(new ConsoleMavenTransferListener(System.out, printResourceNames));
     }
 
     protected TransferListener getBatchTransferListener() {

maven-embedder/src/main/java/org/apache/maven/cli/transfer/ConsoleMavenTransferListener.java

@@ -49,21 +49,21 @@ public ConsoleMavenTransferListener(PrintStream out, boolean printResourceNames)
     }
 
     @Override
-    public synchronized void transferInitiated(TransferEvent event) {
+    public void transferInitiated(TransferEvent event) {
         overridePreviousTransfer(event);
 
         super.transferInitiated(event);
     }
 
     @Override
-    public synchronized void transferCorrupted(TransferEvent event) throws TransferCancelledException {
+    public void transferCorrupted(TransferEvent event) throws TransferCancelledException {
         overridePreviousTransfer(event);
 
         super.transferCorrupted(event);
     }
 
     @Override
-    public synchronized void transferProgressed(TransferEvent event) throws TransferCancelledException {
+    public void transferProgressed(TransferEvent event) throws TransferCancelledException {
         TransferResource resource = event.getResource();
         transfers.put(resource, event.getTransferredBytes());
 
@@ -120,15 +120,15 @@ private void pad(StringBuilder buffer, int spaces) {
     }
 
     @Override
-    public synchronized void transferSucceeded(TransferEvent event) {
+    public void transferSucceeded(TransferEvent event) {
         transfers.remove(event.getResource());
         overridePreviousTransfer(event);
 
         super.transferSucceeded(event);
     }
 
     @Override
-    public synchronized void transferFailed(TransferEvent event) {
+    public void transferFailed(TransferEvent event) {
         transfers.remove(event.getResource());
         overridePreviousTransfer(event);
 

maven-embedder/src/main/java/org/apache/maven/cli/transfer/SimplexTransferListener.java

@@ -0,0 +1,231 @@
+/*
+ * 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.maven.cli.transfer;
+
+import java.io.File;
+import java.util.ArrayList;
+import java.util.List;
+import java.util.concurrent.ArrayBlockingQueue;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.CountDownLatch;
+import java.util.function.Consumer;
+
+import org.eclipse.aether.transfer.AbstractTransferListener;
+import org.eclipse.aether.transfer.TransferCancelledException;
+import org.eclipse.aether.transfer.TransferEvent;
+import org.eclipse.aether.transfer.TransferListener;
+import org.slf4j.Logger;
+import org.slf4j.LoggerFactory;
+
+import static java.util.Objects.requireNonNull;
+
+/**
+ * A {@link TransferListener} implementation that wraps another delegate {@link TransferListener} but makes it run
+ * on single thread, keeping the listener logic simple. This listener also blocks on last transfer event to allow
+ * output to perform possible cleanup. It spawns a daemon thread to consume queued events that may fall in even
+ * concurrently.
+ *
+ * @since 3.9.7
+ */
+public final class SimplexTransferListener extends AbstractTransferListener {
+    private static final Logger LOGGER = LoggerFactory.getLogger(SimplexTransferListener.class);
+    private static final int QUEUE_SIZE = 1024;
+    private static final int BATCH_MAX_SIZE = 500;
+    private final TransferListener delegate;
+    private final int batchMaxSize;
+    private final boolean blockOnLastEvent;
+    private final ArrayBlockingQueue<Exchange> eventQueue;
+
+    /**
+     * Constructor that makes passed in delegate run on single thread, and will block on last event.
+     */
+    public SimplexTransferListener(TransferListener delegate) {
+        this(delegate, QUEUE_SIZE, BATCH_MAX_SIZE, true);
+    }
+
+    /**
+     * Constructor that may alter behaviour of this listener.
+     *
+     * @param delegate The delegate that should run on single thread.
+     * @param queueSize The event queue size (default {@code 1024}).
+     * @param batchMaxSize The maximum batch size delegate should receive (default {@code 500}).
+     * @param blockOnLastEvent Should this listener block on last transfer end (completed or corrupted) block? (default {@code true}).
+     */
+    public SimplexTransferListener(
+            TransferListener delegate, int queueSize, int batchMaxSize, boolean blockOnLastEvent) {
+        this.delegate = requireNonNull(delegate);
+        if (queueSize < 1 || batchMaxSize < 1) {
+            throw new IllegalArgumentException("Queue and batch sizes must be greater than 1");
+        }
+        this.batchMaxSize = batchMaxSize;
+        this.blockOnLastEvent = blockOnLastEvent;
+
+        this.eventQueue = new ArrayBlockingQueue<>(queueSize);
+        Thread updater = new Thread(this::feedConsumer);
+        updater.setDaemon(true);
+        updater.start();
+    }
+
+    public TransferListener getDelegate() {
+        return delegate;
+    }
+
+    private void feedConsumer() {
+        final ArrayList<Exchange> batch = new ArrayList<>(batchMaxSize);
+        try {
+            while (true) {
+                batch.clear();
+                if (eventQueue.drainTo(batch, BATCH_MAX_SIZE) == 0) {
+                    batch.add(eventQueue.take());
+                }
+                demux(batch);
+            }
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private void demux(List<Exchange> exchanges) {
+        for (Exchange exchange : exchanges) {
+            exchange.process(transferEvent -> {
+                TransferEvent.EventType type = transferEvent.getType();
+                try {
+                    switch (type) {
+                        case INITIATED:
+                            delegate.transferInitiated(transferEvent);
+                            break;
+                        case STARTED:
+                            delegate.transferStarted(transferEvent);
+                            break;
+                        case PROGRESSED:
+                            delegate.transferProgressed(transferEvent);
+                            break;
+                        case CORRUPTED:
+                            delegate.transferCorrupted(transferEvent);
+                            break;
+                        case SUCCEEDED:
+                            delegate.transferSucceeded(transferEvent);
+                            break;
+                        case FAILED:
+                            delegate.transferFailed(transferEvent);
+                            break;
+                        default:
+                            LOGGER.warn("Invalid TransferEvent.EventType={}; ignoring it", type);
+                    }
+                } catch (TransferCancelledException e) {
+                    ongoing.put(transferEvent.getResource().getFile(), Boolean.FALSE);
+                }
+            });
+        }
+    }
+
+    private void put(TransferEvent event, boolean last) {
+        try {
+            Exchange exchange;
+            if (blockOnLastEvent && last) {
+                exchange = new BlockingExchange(event);
+            } else {
+                exchange = new Exchange(event);
+            }
+            eventQueue.put(exchange);
+            exchange.waitForProcessed();
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
+        }
+    }
+
+    private final ConcurrentHashMap<File, Boolean> ongoing = new ConcurrentHashMap<>();
+
+    @Override
+    public void transferInitiated(TransferEvent event) {
+        ongoing.putIfAbsent(event.getResource().getFile(), Boolean.TRUE);
+        put(event, false);
+    }
+
+    @Override
+    public void transferStarted(TransferEvent event) throws TransferCancelledException {
+        if (ongoing.get(event.getResource().getFile()) == Boolean.FALSE) {
+            throw new TransferCancelledException();
+        }
+        put(event, false);
+    }
+
+    @Override
+    public void transferProgressed(TransferEvent event) throws TransferCancelledException {
+        if (ongoing.get(event.getResource().getFile()) == Boolean.FALSE) {
+            throw new TransferCancelledException();
+        }
+        put(event, false);
+    }
+
+    @Override
+    public void transferCorrupted(TransferEvent event) throws TransferCancelledException {
+        if (ongoing.get(event.getResource().getFile()) == Boolean.FALSE) {
+            throw new TransferCancelledException();
+        }
+        put(event, false);
+    }
+
+    @Override
+    public void transferSucceeded(TransferEvent event) {
+        ongoing.remove(event.getResource().getFile());
+        put(event, ongoing.isEmpty());
+    }
+
+    @Override
+    public void transferFailed(TransferEvent event) {
+        ongoing.remove(event.getResource().getFile());
+        put(event, ongoing.isEmpty());
+    }
+
+    private static class Exchange {
+        private final TransferEvent event;
+
+        private Exchange(TransferEvent event) {
+            this.event = event;
+        }
+
+        public void process(Consumer<TransferEvent> consumer) {
+            consumer.accept(event);
+        }
+
+        public void waitForProcessed() throws InterruptedException {
+            // nothing, is async
+        }
+    }
+
+    private static class BlockingExchange extends Exchange {
+        private final CountDownLatch latch = new CountDownLatch(1);
+
+        private BlockingExchange(TransferEvent event) {
+            super(event);
+        }
+
+        @Override
+        public void process(Consumer<TransferEvent> consumer) {
+            super.process(consumer);
+            latch.countDown();
+        }
+
+        @Override
+        public void waitForProcessed() throws InterruptedException {
+            latch.await();
+        }
+    }
+}

maven-embedder/src/test/java/org/apache/maven/cli/transfer/SimplexTransferListenerTest.java

@@ -0,0 +1,86 @@
+/*
+ * 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.maven.cli.transfer;
+
+import java.io.File;
+
+import org.eclipse.aether.DefaultRepositorySystemSession;
+import org.eclipse.aether.transfer.TransferCancelledException;
+import org.eclipse.aether.transfer.TransferEvent;
+import org.eclipse.aether.transfer.TransferListener;
+import org.eclipse.aether.transfer.TransferResource;
+import org.junit.Test;
+
+import static org.junit.Assert.fail;
+
+public class SimplexTransferListenerTest {
+    @Test
+    public void cancellation() throws InterruptedException {
+        TransferListener delegate = new TransferListener() {
+            @Override
+            public void transferInitiated(TransferEvent event) throws TransferCancelledException {
+                throw new TransferCancelledException();
+            }
+
+            @Override
+            public void transferStarted(TransferEvent event) throws TransferCancelledException {
+                throw new TransferCancelledException();
+            }
+
+            @Override
+            public void transferProgressed(TransferEvent event) throws TransferCancelledException {
+                throw new TransferCancelledException();
+            }
+
+            @Override
+            public void transferCorrupted(TransferEvent event) throws TransferCancelledException {
+                throw new TransferCancelledException();
+            }
+
+            @Override
+            public void transferSucceeded(TransferEvent event) {}
+
+            @Override
+            public void transferFailed(TransferEvent event) {}
+        };
+
+        SimplexTransferListener listener = new SimplexTransferListener(delegate);
+
+        TransferResource resource =
+                new TransferResource(null, null, "http://maven.org/test/test-resource", new File("file"), null);
+        DefaultRepositorySystemSession session = new DefaultRepositorySystemSession();
+
+        // for technical reasons we cannot throw here, even if delegate does cancel transfer
+        listener.transferInitiated(new TransferEvent.Builder(session, resource)
+                .setType(TransferEvent.EventType.INITIATED)
+                .build());
+
+        Thread.sleep(500); // to make sure queue is processed, cancellation applied
+
+        // subsequent call will cancel
+        try {
+            listener.transferStarted(new TransferEvent.Builder(session, resource)
+                    .resetType(TransferEvent.EventType.STARTED)
+                    .build());
+            fail("should throw");
+        } catch (TransferCancelledException e) {
+            // good
+        }
+    }
+}