Use FileArtifactValue#setContentsProxy for remote repo contents cache files

Even though expiration times don't matter in Bazel (they aren't honored), supporting the contents proxy optimization avoids Skyframe invalidation when external repo files are materialized later.

Author: fmeum

src/main/java/com/google/devtools/build/lib/actions/FileArtifactValue.java

@@ -395,6 +395,11 @@ public static FileArtifactValue createForInlineFile(byte[] bytes, HashFunction h
     return new InlineFileArtifactValue(bytes, hashFunction.hashBytes(bytes).asBytes());
   }
 
+  /**
+   * Prefer {@link #createForRemoteFileWithMaterializationData} if the remote file may be
+   * materialized in the local filesystem at a later point as this variant supports {@link
+   * #setContentsProxy}.
+   */
   public static FileArtifactValue createForRemoteFile(byte[] digest, long size, int locationIndex) {
     return new RemoteFileArtifactValue(digest, size, locationIndex);
   }

src/main/java/com/google/devtools/build/lib/remote/RemoteExternalOverlayFileSystem.java

@@ -60,6 +60,8 @@
 import java.io.InterruptedIOException;
 import java.io.OutputStream;
 import java.nio.channels.SeekableByteChannel;
+import java.time.Duration;
+import java.time.Instant;
 import java.util.ArrayList;
 import java.util.Collection;
 import java.util.List;
@@ -98,6 +100,7 @@ public final class RemoteExternalOverlayFileSystem extends FileSystem {
   @Nullable private String buildRequestId;
   @Nullable private String commandId;
   @Nullable private MemoizingEvaluator evaluator;
+  @Nullable private Duration remoteCacheTtl;
   @Nullable private ExecutorService materializationExecutor;
 
   public RemoteExternalOverlayFileSystem(PathFragment externalDirectory, FileSystem nativeFs) {
@@ -115,21 +118,24 @@ public void beforeCommand(
       Reporter reporter,
       String buildRequestId,
       String commandId,
-      MemoizingEvaluator evaluator) {
+      MemoizingEvaluator evaluator,
+      Duration remoteCacheTtl) {
     checkState(
         this.cache == null
             && this.inputPrefetcher == null
             && this.reporter == null
             && this.buildRequestId == null
             && this.commandId == null
             && this.evaluator == null
+            && this.remoteCacheTtl == null
             && this.materializationExecutor == null);
     this.cache = cache;
     this.inputPrefetcher = inputPrefetcher;
     this.reporter = reporter;
     this.buildRequestId = buildRequestId;
     this.commandId = commandId;
     this.evaluator = evaluator;
+    this.remoteCacheTtl = remoteCacheTtl;
     this.materializationExecutor =
         Executors.newThreadPerTaskExecutor(
             Thread.ofVirtual().name("remote-repo-materialization-", 0).factory());
@@ -146,6 +152,7 @@ public void afterCommand() {
     this.reporter = null;
     this.buildRequestId = null;
     this.commandId = null;
+    this.remoteCacheTtl = null;
     // Materializations happen synchronously and upon request by other repo rules, so there is no
     // reason to await their orderly completion in afterCommand.
     materializationExecutor.shutdownNow();
@@ -193,7 +200,12 @@ public boolean injectRemoteRepo(RepositoryName repo, Tree remoteContents, String
     var repoDir = externalDirectory.getChild(repo.getName());
     var filesToPrefetch = new ArrayList<PathFragment>();
     injectRecursively(
-        externalFs, repoDir, remoteContents.getRoot(), childMap, filesToPrefetch::add);
+        externalFs,
+        repoDir,
+        remoteContents.getRoot(),
+        childMap,
+        filesToPrefetch::add,
+        Instant.now().plus(remoteCacheTtl));
     try {
       // TODO: This prefetches a large number of small files. Investigate whether BatchReadBlobs
       // would be more efficient.
@@ -220,7 +232,8 @@ private static void injectRecursively(
       PathFragment path,
       Directory dir,
       ImmutableMap<Digest, Directory> childMap,
-      Consumer<PathFragment> filesToPrefetch)
+      Consumer<PathFragment> filesToPrefetch,
+      Instant expirationTime)
       throws IOException {
     fs.createDirectoryAndParents(path);
     for (var file : dir.getFilesList()) {
@@ -230,10 +243,15 @@ private static void injectRecursively(
       }
       fs.injectFile(
           filePath,
-          FileArtifactValue.createForRemoteFile(
+          // Using the *WithMaterializationData variant ensures that the file benefits from the
+          // FileContentsProxy optimization to avoid widespread invalidation when it is
+          // materialized later, even if expiration times aren't relevant (depends on the usage
+          // of the lease extension).
+          FileArtifactValue.createForRemoteFileWithMaterializationData(
               DigestUtil.toBinaryDigest(file.getDigest()),
               file.getDigest().getSizeBytes(),
-              /* locationIndex= */ 1));
+              /* locationIndex= */ 1,
+              expirationTime));
       fs.setExecutable(filePath, file.getIsExecutable());
       // The RE API does not track whether a file is readable or writable. We choose to make all
       // files readable and not writable to ensure that other repo rules can't accidentally modify
@@ -253,7 +271,7 @@ private static void injectRecursively(
             "Directory %s with digest %s not found in tree"
                 .formatted(subdirPath, subdirNode.getDigest().getHash()));
       }
-      injectRecursively(fs, subdirPath, subdir, childMap, filesToPrefetch);
+      injectRecursively(fs, subdirPath, subdir, childMap, filesToPrefetch, expirationTime);
     }
   }
 

src/main/java/com/google/devtools/build/lib/remote/RemoteModule.java

@@ -810,7 +810,8 @@ public void beforeCommand(CommandEnvironment env) throws AbruptExitException {
           env.getReporter(),
           buildRequestId,
           invocationId,
-          env.getSkyframeExecutor().getEvaluator());
+          env.getSkyframeExecutor().getEvaluator(),
+          remoteOptions.remoteCacheTtl);
     }
 
     buildEventArtifactUploaderFactoryDelegate.init(