src/test/java/com/google/devtools/build/lib/remote/ActionInputPrefetcherTestBase.java - bazel - Git at Google

 // Copyright 2019 The Bazel Authors. All rights reserved.
 //
 // Licensed 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 com.google.devtools.build.lib.remote;

 import static com.google.common.base.Throwables.throwIfInstanceOf;
 import static com.google.common.truth.Truth.assertThat;
 import static java.nio.charset.StandardCharsets.UTF_8;
 import static org.junit.Assert.assertThrows;
 import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.doAnswer;
 import static org.mockito.Mockito.spy;

 import com.google.common.collect.ImmutableList;
 import com.google.common.collect.ImmutableMap;
 import com.google.common.hash.HashCode;
 import com.google.common.util.concurrent.Futures;
 import com.google.common.util.concurrent.ListenableFuture;
 import com.google.common.util.concurrent.SettableFuture;
 import com.google.devtools.build.lib.actions.ActionInput;
 import com.google.devtools.build.lib.actions.Artifact;
 import com.google.devtools.build.lib.actions.ArtifactRoot;
 import com.google.devtools.build.lib.actions.ArtifactRoot.RootType;
 import com.google.devtools.build.lib.actions.FileArtifactValue;
 import com.google.devtools.build.lib.actions.FileArtifactValue.RemoteFileArtifactValue;
 import com.google.devtools.build.lib.actions.MetadataProvider;
 import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
 import com.google.devtools.build.lib.clock.JavaClock;
 import com.google.devtools.build.lib.remote.common.BulkTransferException;
 import com.google.devtools.build.lib.remote.util.StaticMetadataProvider;
 import com.google.devtools.build.lib.remote.util.TempPathGenerator;
 import com.google.devtools.build.lib.vfs.DigestHashFunction;
 import com.google.devtools.build.lib.vfs.FileSystem;
 import com.google.devtools.build.lib.vfs.FileSystemUtils;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
 import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 import java.util.concurrent.ExecutionException;
 import java.util.concurrent.Semaphore;
 import java.util.concurrent.atomic.AtomicBoolean;
 import java.util.function.Supplier;
 import org.junit.Before;
 import org.junit.Test;

 /** Base test class for {@link AbstractActionInputPrefetcher} implementations. */
 public abstract class ActionInputPrefetcherTestBase {
   protected static final DigestHashFunction HASH_FUNCTION = DigestHashFunction.SHA256;

   protected FileSystem fs;
   protected Path execRoot;
   protected ArtifactRoot artifactRoot;
   protected TempPathGenerator tempPathGenerator;

   @Before
   public void setUp() throws IOException {
     fs = new InMemoryFileSystem(new JavaClock(), HASH_FUNCTION);
     execRoot = fs.getPath("/exec");
     execRoot.createDirectoryAndParents();
     artifactRoot = ArtifactRoot.asDerivedRoot(execRoot, RootType.Output, "root");
     artifactRoot.getRoot().asPath().createDirectoryAndParents();
     Path tempDir = fs.getPath("/tmp");
     tempDir.createDirectoryAndParents();
     tempPathGenerator = new TempPathGenerator(tempDir);
   }

   protected Artifact createRemoteArtifact(
       String pathFragment,
       String contents,
       Map<ActionInput, FileArtifactValue> metadata,
       Map<HashCode, byte[]> cas) {
     Path p = artifactRoot.getRoot().getRelative(pathFragment);
     Artifact a = ActionsTestUtil.createArtifact(artifactRoot, p);
     byte[] contentsBytes = contents.getBytes(UTF_8);
     HashCode hashCode = HASH_FUNCTION.getHashFunction().hashBytes(contentsBytes);
     FileArtifactValue f =
         new RemoteFileArtifactValue(
             hashCode.asBytes(), contentsBytes.length, /* locationIndex= */ 1, "action-id");
     metadata.put(a, f);
     cas.put(hashCode, contentsBytes);
     return a;
   }

   protected abstract AbstractActionInputPrefetcher createPrefetcher(Map<HashCode, byte[]> cas);

   @Test
   public void prefetchFiles_downloadRemoteFiles() throws Exception {
     Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
     Map<HashCode, byte[]> cas = new HashMap<>();
     Artifact a1 = createRemoteArtifact("file1", "hello world", metadata, cas);
     Artifact a2 = createRemoteArtifact("file2", "fizz buzz", metadata, cas);
     MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);
     AbstractActionInputPrefetcher prefetcher = createPrefetcher(cas);

     wait(prefetcher.prefetchFiles(metadata.keySet(), metadataProvider));

     assertThat(FileSystemUtils.readContent(a1.getPath(), UTF_8)).isEqualTo("hello world");
     assertThat(a1.getPath().isExecutable()).isTrue();
     assertThat(FileSystemUtils.readContent(a2.getPath(), UTF_8)).isEqualTo("fizz buzz");
     assertThat(a2.getPath().isExecutable()).isTrue();
     assertThat(prefetcher.downloadedFiles()).hasSize(2);
     assertThat(prefetcher.downloadedFiles()).containsAtLeast(a1.getPath(), a2.getPath());
     assertThat(prefetcher.downloadsInProgress()).isEmpty();
   }

   @Test
   public void prefetchFiles_missingFiles_fails() throws Exception {
     Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
     Artifact a = createRemoteArtifact("file1", "hello world", metadata, /* cas= */ new HashMap<>());
     MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);
     AbstractActionInputPrefetcher prefetcher = createPrefetcher(new HashMap<>());

     assertThrows(
         BulkTransferException.class,
         () -> wait(prefetcher.prefetchFiles(ImmutableList.of(a), metadataProvider)));

     assertThat(prefetcher.downloadedFiles()).isEmpty();
     assertThat(prefetcher.downloadsInProgress()).isEmpty();
   }

   @Test
   public void prefetchFiles_ignoreNonRemoteFiles() throws Exception {
     // Test that files that are not remote are not downloaded

     Path p = execRoot.getRelative(artifactRoot.getExecPath()).getRelative("file1");
     FileSystemUtils.writeContent(p, UTF_8, "hello world");
     Artifact a = ActionsTestUtil.createArtifact(artifactRoot, p);
     FileArtifactValue f = FileArtifactValue.createForTesting(a);
     MetadataProvider metadataProvider = new StaticMetadataProvider(ImmutableMap.of(a, f));
     AbstractActionInputPrefetcher prefetcher = createPrefetcher(new HashMap<>());

     wait(prefetcher.prefetchFiles(ImmutableList.of(a), metadataProvider));

     assertThat(prefetcher.downloadedFiles()).isEmpty();
     assertThat(prefetcher.downloadsInProgress()).isEmpty();
   }

   @Test
   public void prefetchFiles_multipleThreads_downloadIsCancelled() throws Exception {
     // Test shared downloads are cancelled if all threads/callers are interrupted

     // arrange
     Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
     Map<HashCode, byte[]> cas = new HashMap<>();
     Artifact artifact = createRemoteArtifact("file1", "hello world", metadata, cas);
     MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);

     AbstractActionInputPrefetcher prefetcher = spy(createPrefetcher(cas));
     SettableFuture<Void> downloadThatNeverFinishes = SettableFuture.create();
     mockDownload(prefetcher, cas, () -> downloadThatNeverFinishes);

     Thread cancelledThread1 =
         new Thread(
             () -> {
               try {
                 wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
               } catch (IOException | InterruptedException ignored) {
                 // do nothing
               }
             });

     Thread cancelledThread2 =
         new Thread(
             () -> {
               try {
                 wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
               } catch (IOException | InterruptedException ignored) {
                 // do nothing
               }
             });

     // act
     cancelledThread1.start();
     cancelledThread2.start();
     cancelledThread1.interrupt();
     cancelledThread2.interrupt();
     cancelledThread1.join();
     cancelledThread2.join();

     // assert
     assertThat(downloadThatNeverFinishes.isCancelled()).isTrue();
     assertThat(artifact.getPath().exists()).isFalse();
     assertThat(tempPathGenerator.getTempDir().getDirectoryEntries()).isEmpty();
   }

   @Test
   public void prefetchFiles_multipleThreads_downloadIsNotCancelledByOtherThreads()
       throws Exception {
     // Test multiple threads can share downloads, but do not cancel each other when interrupted

     // arrange
     Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
     Map<HashCode, byte[]> cas = new HashMap<>();
     Artifact artifact = createRemoteArtifact("file1", "hello world", metadata, cas);
     MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);
     SettableFuture<Void> download = SettableFuture.create();
     AbstractActionInputPrefetcher prefetcher = spy(createPrefetcher(cas));
     mockDownload(prefetcher, cas, () -> download);
     Thread cancelledThread =
         new Thread(
             () -> {
               try {
                 wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
               } catch (IOException | InterruptedException ignored) {
                 // do nothing
               }
             });

     AtomicBoolean successful = new AtomicBoolean(false);
     Thread successfulThread =
         new Thread(
             () -> {
               try {
                 wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
                 successful.set(true);
               } catch (IOException | InterruptedException ignored) {
                 // do nothing
               }
             });
     cancelledThread.start();
     successfulThread.start();
     while (true) {
       if (prefetcher
               .getDownloadCache()
               .getSubscriberCount(execRoot.getRelative(artifact.getExecPath()))
           == 2) {
         break;
       }
     }

     // act
     cancelledThread.interrupt();
     cancelledThread.join();
     // simulate the download finishing
     assertThat(download.isCancelled()).isFalse();
     download.set(null);
     successfulThread.join();

     // assert
     assertThat(successful.get()).isTrue();
     assertThat(FileSystemUtils.readContent(artifact.getPath(), UTF_8)).isEqualTo("hello world");
   }

   @Test
   public void downloadFile_downloadRemoteFiles() throws Exception {
     Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
     Map<HashCode, byte[]> cas = new HashMap<>();
     Artifact a1 = createRemoteArtifact("file1", "hello world", metadata, cas);
     AbstractActionInputPrefetcher prefetcher = createPrefetcher(cas);

     prefetcher.downloadFile(a1.getPath(), metadata.get(a1));

     assertThat(FileSystemUtils.readContent(a1.getPath(), UTF_8)).isEqualTo("hello world");
     assertThat(a1.getPath().isExecutable()).isTrue();
     assertThat(a1.getPath().isReadable()).isTrue();
     assertThat(a1.getPath().isWritable()).isFalse();
   }

   @Test
   public void downloadFile_onInterrupt_deletePartialDownloadedFile() throws Exception {
     Semaphore startSemaphore = new Semaphore(0);
     Semaphore endSemaphore = new Semaphore(0);
     Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
     Map<HashCode, byte[]> cas = new HashMap<>();
     Artifact a1 = createRemoteArtifact("file1", "hello world", metadata, cas);
     AbstractActionInputPrefetcher prefetcher = spy(createPrefetcher(cas));
     mockDownload(
         prefetcher,
         cas,
         () -> {
           startSemaphore.release();
           return SettableFuture.create(); // A future that never complete so we can interrupt later
         });

     AtomicBoolean interrupted = new AtomicBoolean(false);
     Thread t =
         new Thread(
             () -> {
               try {
                 prefetcher.downloadFile(a1.getPath(), metadata.get(a1));
               } catch (IOException ignored) {
                 // Intentionally left empty
               } catch (InterruptedException e) {
                 interrupted.set(true);
               }
               endSemaphore.release();
             });
     t.start();
     startSemaphore.acquire();
     t.interrupt();
     endSemaphore.acquire();

     assertThat(interrupted.get()).isTrue();
     assertThat(a1.getPath().exists()).isFalse();
     assertThat(tempPathGenerator.getTempDir().getDirectoryEntries()).isEmpty();
   }

   protected static void wait(ListenableFuture<Void> future)
       throws IOException, InterruptedException {
     try {
       future.get();
     } catch (ExecutionException e) {
       Throwable cause = e.getCause();
       if (cause != null) {
         throwIfInstanceOf(cause, IOException.class);
         throwIfInstanceOf(cause, InterruptedException.class);
         throwIfInstanceOf(cause, RuntimeException.class);
       }
       throw new IOException(e);
     } catch (InterruptedException e) {
       future.cancel(/*mayInterruptIfRunning=*/ true);
       throw e;
     }
   }

   protected static void mockDownload(
       AbstractActionInputPrefetcher prefetcher,
       Map<HashCode, byte[]> cas,
       Supplier<ListenableFuture<Void>> resultSupplier)
       throws IOException {
     doAnswer(
             invocation -> {
               Path path = invocation.getArgument(0);
               FileArtifactValue metadata = invocation.getArgument(1);
               byte[] content = cas.get(HashCode.fromBytes(metadata.getDigest()));
               if (content == null) {
                 return Futures.immediateFailedFuture(new IOException("Not found"));
               }
               FileSystemUtils.writeContent(path, content);
               return resultSupplier.get();
             })
         .when(prefetcher)
         .doDownloadFile(any(), any());
   }
 }
	// Copyright 2019 The Bazel Authors. All rights reserved.
	//
	// Licensed 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 com.google.devtools.build.lib.remote;

	import static com.google.common.base.Throwables.throwIfInstanceOf;
	import static com.google.common.truth.Truth.assertThat;
	import static java.nio.charset.StandardCharsets.UTF_8;
	import static org.junit.Assert.assertThrows;
	import static org.mockito.ArgumentMatchers.any;
	import static org.mockito.Mockito.doAnswer;
	import static org.mockito.Mockito.spy;

	import com.google.common.collect.ImmutableList;
	import com.google.common.collect.ImmutableMap;
	import com.google.common.hash.HashCode;
	import com.google.common.util.concurrent.Futures;
	import com.google.common.util.concurrent.ListenableFuture;
	import com.google.common.util.concurrent.SettableFuture;
	import com.google.devtools.build.lib.actions.ActionInput;
	import com.google.devtools.build.lib.actions.Artifact;
	import com.google.devtools.build.lib.actions.ArtifactRoot;
	import com.google.devtools.build.lib.actions.ArtifactRoot.RootType;
	import com.google.devtools.build.lib.actions.FileArtifactValue;
	import com.google.devtools.build.lib.actions.FileArtifactValue.RemoteFileArtifactValue;
	import com.google.devtools.build.lib.actions.MetadataProvider;
	import com.google.devtools.build.lib.actions.util.ActionsTestUtil;
	import com.google.devtools.build.lib.clock.JavaClock;
	import com.google.devtools.build.lib.remote.common.BulkTransferException;
	import com.google.devtools.build.lib.remote.util.StaticMetadataProvider;
	import com.google.devtools.build.lib.remote.util.TempPathGenerator;
	import com.google.devtools.build.lib.vfs.DigestHashFunction;
	import com.google.devtools.build.lib.vfs.FileSystem;
	import com.google.devtools.build.lib.vfs.FileSystemUtils;
	import com.google.devtools.build.lib.vfs.Path;
	import com.google.devtools.build.lib.vfs.inmemoryfs.InMemoryFileSystem;
	import java.io.IOException;
	import java.util.HashMap;
	import java.util.Map;
	import java.util.concurrent.ExecutionException;
	import java.util.concurrent.Semaphore;
	import java.util.concurrent.atomic.AtomicBoolean;
	import java.util.function.Supplier;
	import org.junit.Before;
	import org.junit.Test;

	/** Base test class for {@link AbstractActionInputPrefetcher} implementations. */
	public abstract class ActionInputPrefetcherTestBase {
	protected static final DigestHashFunction HASH_FUNCTION = DigestHashFunction.SHA256;

	protected FileSystem fs;
	protected Path execRoot;
	protected ArtifactRoot artifactRoot;
	protected TempPathGenerator tempPathGenerator;

	@Before
	public void setUp() throws IOException {
	fs = new InMemoryFileSystem(new JavaClock(), HASH_FUNCTION);
	execRoot = fs.getPath("/exec");
	execRoot.createDirectoryAndParents();
	artifactRoot = ArtifactRoot.asDerivedRoot(execRoot, RootType.Output, "root");
	artifactRoot.getRoot().asPath().createDirectoryAndParents();
	Path tempDir = fs.getPath("/tmp");
	tempDir.createDirectoryAndParents();
	tempPathGenerator = new TempPathGenerator(tempDir);
	}

	protected Artifact createRemoteArtifact(
	String pathFragment,
	String contents,
	Map<ActionInput, FileArtifactValue> metadata,
	Map<HashCode, byte[]> cas) {
	Path p = artifactRoot.getRoot().getRelative(pathFragment);
	Artifact a = ActionsTestUtil.createArtifact(artifactRoot, p);
	byte[] contentsBytes = contents.getBytes(UTF_8);
	HashCode hashCode = HASH_FUNCTION.getHashFunction().hashBytes(contentsBytes);
	FileArtifactValue f =
	new RemoteFileArtifactValue(
	hashCode.asBytes(), contentsBytes.length, /* locationIndex= */ 1, "action-id");
	metadata.put(a, f);
	cas.put(hashCode, contentsBytes);
	return a;
	}

	protected abstract AbstractActionInputPrefetcher createPrefetcher(Map<HashCode, byte[]> cas);

	@Test
	public void prefetchFiles_downloadRemoteFiles() throws Exception {
	Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
	Map<HashCode, byte[]> cas = new HashMap<>();
	Artifact a1 = createRemoteArtifact("file1", "hello world", metadata, cas);
	Artifact a2 = createRemoteArtifact("file2", "fizz buzz", metadata, cas);
	MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);
	AbstractActionInputPrefetcher prefetcher = createPrefetcher(cas);

	wait(prefetcher.prefetchFiles(metadata.keySet(), metadataProvider));

	assertThat(FileSystemUtils.readContent(a1.getPath(), UTF_8)).isEqualTo("hello world");
	assertThat(a1.getPath().isExecutable()).isTrue();
	assertThat(FileSystemUtils.readContent(a2.getPath(), UTF_8)).isEqualTo("fizz buzz");
	assertThat(a2.getPath().isExecutable()).isTrue();
	assertThat(prefetcher.downloadedFiles()).hasSize(2);
	assertThat(prefetcher.downloadedFiles()).containsAtLeast(a1.getPath(), a2.getPath());
	assertThat(prefetcher.downloadsInProgress()).isEmpty();
	}

	@Test
	public void prefetchFiles_missingFiles_fails() throws Exception {
	Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
	Artifact a = createRemoteArtifact("file1", "hello world", metadata, /* cas= */ new HashMap<>());
	MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);
	AbstractActionInputPrefetcher prefetcher = createPrefetcher(new HashMap<>());

	assertThrows(
	BulkTransferException.class,
	() -> wait(prefetcher.prefetchFiles(ImmutableList.of(a), metadataProvider)));

	assertThat(prefetcher.downloadedFiles()).isEmpty();
	assertThat(prefetcher.downloadsInProgress()).isEmpty();
	}

	@Test
	public void prefetchFiles_ignoreNonRemoteFiles() throws Exception {
	// Test that files that are not remote are not downloaded

	Path p = execRoot.getRelative(artifactRoot.getExecPath()).getRelative("file1");
	FileSystemUtils.writeContent(p, UTF_8, "hello world");
	Artifact a = ActionsTestUtil.createArtifact(artifactRoot, p);
	FileArtifactValue f = FileArtifactValue.createForTesting(a);
	MetadataProvider metadataProvider = new StaticMetadataProvider(ImmutableMap.of(a, f));
	AbstractActionInputPrefetcher prefetcher = createPrefetcher(new HashMap<>());

	wait(prefetcher.prefetchFiles(ImmutableList.of(a), metadataProvider));

	assertThat(prefetcher.downloadedFiles()).isEmpty();
	assertThat(prefetcher.downloadsInProgress()).isEmpty();
	}

	@Test
	public void prefetchFiles_multipleThreads_downloadIsCancelled() throws Exception {
	// Test shared downloads are cancelled if all threads/callers are interrupted

	// arrange
	Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
	Map<HashCode, byte[]> cas = new HashMap<>();
	Artifact artifact = createRemoteArtifact("file1", "hello world", metadata, cas);
	MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);

	AbstractActionInputPrefetcher prefetcher = spy(createPrefetcher(cas));
	SettableFuture<Void> downloadThatNeverFinishes = SettableFuture.create();
	mockDownload(prefetcher, cas, () -> downloadThatNeverFinishes);

	Thread cancelledThread1 =
	new Thread(
	() -> {
	try {
	wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
	} catch (IOException \| InterruptedException ignored) {
	// do nothing
	}
	});

	Thread cancelledThread2 =
	new Thread(
	() -> {
	try {
	wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
	} catch (IOException \| InterruptedException ignored) {
	// do nothing
	}
	});

	// act
	cancelledThread1.start();
	cancelledThread2.start();
	cancelledThread1.interrupt();
	cancelledThread2.interrupt();
	cancelledThread1.join();
	cancelledThread2.join();

	// assert
	assertThat(downloadThatNeverFinishes.isCancelled()).isTrue();
	assertThat(artifact.getPath().exists()).isFalse();
	assertThat(tempPathGenerator.getTempDir().getDirectoryEntries()).isEmpty();
	}

	@Test
	public void prefetchFiles_multipleThreads_downloadIsNotCancelledByOtherThreads()
	throws Exception {
	// Test multiple threads can share downloads, but do not cancel each other when interrupted

	// arrange
	Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
	Map<HashCode, byte[]> cas = new HashMap<>();
	Artifact artifact = createRemoteArtifact("file1", "hello world", metadata, cas);
	MetadataProvider metadataProvider = new StaticMetadataProvider(metadata);
	SettableFuture<Void> download = SettableFuture.create();
	AbstractActionInputPrefetcher prefetcher = spy(createPrefetcher(cas));
	mockDownload(prefetcher, cas, () -> download);
	Thread cancelledThread =
	new Thread(
	() -> {
	try {
	wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
	} catch (IOException \| InterruptedException ignored) {
	// do nothing
	}
	});

	AtomicBoolean successful = new AtomicBoolean(false);
	Thread successfulThread =
	new Thread(
	() -> {
	try {
	wait(prefetcher.prefetchFiles(ImmutableList.of(artifact), metadataProvider));
	successful.set(true);
	} catch (IOException \| InterruptedException ignored) {
	// do nothing
	}
	});
	cancelledThread.start();
	successfulThread.start();
	while (true) {
	if (prefetcher
	.getDownloadCache()
	.getSubscriberCount(execRoot.getRelative(artifact.getExecPath()))
	== 2) {
	break;
	}
	}

	// act
	cancelledThread.interrupt();
	cancelledThread.join();
	// simulate the download finishing
	assertThat(download.isCancelled()).isFalse();
	download.set(null);
	successfulThread.join();

	// assert
	assertThat(successful.get()).isTrue();
	assertThat(FileSystemUtils.readContent(artifact.getPath(), UTF_8)).isEqualTo("hello world");
	}

	@Test
	public void downloadFile_downloadRemoteFiles() throws Exception {
	Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
	Map<HashCode, byte[]> cas = new HashMap<>();
	Artifact a1 = createRemoteArtifact("file1", "hello world", metadata, cas);
	AbstractActionInputPrefetcher prefetcher = createPrefetcher(cas);

	prefetcher.downloadFile(a1.getPath(), metadata.get(a1));

	assertThat(FileSystemUtils.readContent(a1.getPath(), UTF_8)).isEqualTo("hello world");
	assertThat(a1.getPath().isExecutable()).isTrue();
	assertThat(a1.getPath().isReadable()).isTrue();
	assertThat(a1.getPath().isWritable()).isFalse();
	}

	@Test
	public void downloadFile_onInterrupt_deletePartialDownloadedFile() throws Exception {
	Semaphore startSemaphore = new Semaphore(0);
	Semaphore endSemaphore = new Semaphore(0);
	Map<ActionInput, FileArtifactValue> metadata = new HashMap<>();
	Map<HashCode, byte[]> cas = new HashMap<>();
	Artifact a1 = createRemoteArtifact("file1", "hello world", metadata, cas);
	AbstractActionInputPrefetcher prefetcher = spy(createPrefetcher(cas));
	mockDownload(
	prefetcher,
	cas,
	() -> {
	startSemaphore.release();
	return SettableFuture.create(); // A future that never complete so we can interrupt later
	});

	AtomicBoolean interrupted = new AtomicBoolean(false);
	Thread t =
	new Thread(
	() -> {
	try {
	prefetcher.downloadFile(a1.getPath(), metadata.get(a1));
	} catch (IOException ignored) {
	// Intentionally left empty
	} catch (InterruptedException e) {
	interrupted.set(true);
	}
	endSemaphore.release();
	});
	t.start();
	startSemaphore.acquire();
	t.interrupt();
	endSemaphore.acquire();

	assertThat(interrupted.get()).isTrue();
	assertThat(a1.getPath().exists()).isFalse();
	assertThat(tempPathGenerator.getTempDir().getDirectoryEntries()).isEmpty();
	}

	protected static void wait(ListenableFuture<Void> future)
	throws IOException, InterruptedException {
	try {
	future.get();
	} catch (ExecutionException e) {
	Throwable cause = e.getCause();
	if (cause != null) {
	throwIfInstanceOf(cause, IOException.class);
	throwIfInstanceOf(cause, InterruptedException.class);
	throwIfInstanceOf(cause, RuntimeException.class);
	}
	throw new IOException(e);
	} catch (InterruptedException e) {
	future.cancel(/mayInterruptIfRunning=/ true);
	throw e;
	}
	}

	protected static void mockDownload(
	AbstractActionInputPrefetcher prefetcher,
	Map<HashCode, byte[]> cas,
	Supplier<ListenableFuture<Void>> resultSupplier)
	throws IOException {
	doAnswer(
	invocation -> {
	Path path = invocation.getArgument(0);
	FileArtifactValue metadata = invocation.getArgument(1);
	byte[] content = cas.get(HashCode.fromBytes(metadata.getDigest()));
	if (content == null) {
	return Futures.immediateFailedFuture(new IOException("Not found"));
	}
	FileSystemUtils.writeContent(path, content);
	return resultSupplier.get();
	})
	.when(prefetcher)
	.doDownloadFile(any(), any());
	}
	}