Report background download for BwoB

When building without the bytes, downloads can happen when Bazel need to fetch inputs for local actions, download outputs of toplevel targets, and etc. The downloads happen silently at the background.

This PR makes output downloads of toplevel targets visible to the UI.

For downloads during the build, the UI looks like:

```
[2 / 5] 2 actions, 1 running
    [Prepa] Executing genrule //:foo
    Executing genrule //:bar; 2s
    Fetching bazel-out/darwin-fastbuild/bin/baz; 50.8 MiB / 1.0 GiB; 4s
```

For downloads after build is completed, the UI looks like:

```
INFO: 2 processes: 1 remote cache hit, 1 internal.
INFO: Build completed successfully, 2 total actions
    Fetching bazel-out/darwin-fastbuild/bin/baz; 48.8 MiB / 1.0 GiB
```

Fixes bazelbuild#17417.

Closes bazelbuild#17604.

PiperOrigin-RevId: 512934756
Change-Id: I502489420ab9b84efb74ceabbe3dd4cb4a7a62e2

src/main/java/com/google/devtools/build/lib/exec/SpawnProgressEvent.java

@@ -28,13 +28,13 @@ public static SpawnProgressEvent create(String resourceId, String progress, bool
   }
 
   /** The id that uniquely determines the progress among all progress events for this spawn. */
-  abstract String progressId();
+  public abstract String progressId();
 
   /** Human readable description of the progress. */
-  abstract String progress();
+  public abstract String progress();
 
   /** Whether the progress reported about is finished already. */
-  abstract boolean finished();
+  public abstract boolean finished();
 
   @Override
   public void postTo(ExtendedEventHandler eventHandler, ActionExecutionMetadata action) {

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

@@ -157,7 +157,11 @@ private boolean shouldDownloadFile(Path path, FileArtifactValue metadata) {
    * @param tempPath the temporary path which the input should be written to.
    */
   protected abstract ListenableFuture<Void> doDownloadFile(
-      Path tempPath, PathFragment execPath, FileArtifactValue metadata, Priority priority)
+      Reporter reporter,
+      Path tempPath,
+      PathFragment execPath,
+      FileArtifactValue metadata,
+      Priority priority)
       throws IOException;
 
   protected void prefetchVirtualActionInput(VirtualActionInput input) throws IOException {}
@@ -309,7 +313,8 @@ private Completable prefetchInputTree(
                   return toTransferResult(
                       toCompletable(
                           () ->
-                              doDownloadFile(tempPath, treeFile.getExecPath(), metadata, priority),
+                              doDownloadFile(
+                                  reporter, tempPath, treeFile.getExecPath(), metadata, priority),
                           directExecutor()));
                 });
 
@@ -455,7 +460,11 @@ private Completable downloadFileNoCheckRx(
                     toCompletable(
                             () ->
                                 doDownloadFile(
-                                    tempPath, finalPath.relativeTo(execRoot), metadata, priority),
+                                    reporter,
+                                    tempPath,
+                                    finalPath.relativeTo(execRoot),
+                                    metadata,
+                                    priority),
                             directExecutor())
                         .doOnComplete(
                             () -> {

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

@@ -14,6 +14,7 @@
 package com.google.devtools.build.lib.remote;
 
 import static com.google.common.base.Preconditions.checkArgument;
+import static com.google.devtools.build.lib.remote.common.ProgressStatusListener.NO_ACTION;
 
 import build.bazel.remote.execution.v2.Digest;
 import build.bazel.remote.execution.v2.RequestMetadata;
@@ -24,7 +25,10 @@
 import com.google.devtools.build.lib.actions.FileArtifactValue;
 import com.google.devtools.build.lib.actions.cache.VirtualActionInput;
 import com.google.devtools.build.lib.actions.cache.VirtualActionInput.EmptyActionInput;
+import com.google.devtools.build.lib.events.ExtendedEventHandler.FetchProgress;
 import com.google.devtools.build.lib.events.Reporter;
+import com.google.devtools.build.lib.exec.SpawnProgressEvent;
+import com.google.devtools.build.lib.remote.RemoteCache.DownloadProgressReporter;
 import com.google.devtools.build.lib.remote.common.BulkTransferException;
 import com.google.devtools.build.lib.remote.common.RemoteActionExecutionContext;
 import com.google.devtools.build.lib.remote.util.DigestUtil;
@@ -90,15 +94,56 @@ protected boolean canDownloadFile(Path path, FileArtifactValue metadata) {
 
   @Override
   protected ListenableFuture<Void> doDownloadFile(
-      Path tempPath, PathFragment execPath, FileArtifactValue metadata, Priority priority)
+      Reporter reporter,
+      Path tempPath,
+      PathFragment execPath,
+      FileArtifactValue metadata,
+      Priority priority)
       throws IOException {
     checkArgument(metadata.isRemote(), "Cannot download file that is not a remote file.");
     RequestMetadata requestMetadata =
         TracingMetadataUtils.buildMetadata(buildRequestId, commandId, metadata.getActionId(), null);
     RemoteActionExecutionContext context = RemoteActionExecutionContext.create(requestMetadata);
 
     Digest digest = DigestUtil.buildDigest(metadata.getDigest(), metadata.getSize());
-    return remoteCache.downloadFile(context, tempPath, digest);
+
+    DownloadProgressReporter downloadProgressReporter;
+    if (priority == Priority.LOW) {
+      // Only report download progress for toplevel outputs
+      downloadProgressReporter =
+          new DownloadProgressReporter(
+              /* includeFile= */ false,
+              progress -> reporter.post(new DownloadProgress(progress)),
+              execPath.toString(),
+              metadata.getSize());
+    } else {
+      downloadProgressReporter = new DownloadProgressReporter(NO_ACTION, "", 0);
+    }
+
+    return remoteCache.downloadFile(context, tempPath, digest, downloadProgressReporter);
+  }
+
+  public static class DownloadProgress implements FetchProgress {
+    private final SpawnProgressEvent progress;
+
+    public DownloadProgress(SpawnProgressEvent progress) {
+      this.progress = progress;
+    }
+
+    @Override
+    public String getResourceIdentifier() {
+      return progress.progressId();
+    }
+
+    @Override
+    public String getProgress() {
+      return progress.progress();
+    }
+
+    @Override
+    public boolean isFinished() {
+      return progress.finished();
+    }
   }
 
   @Override

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

@@ -248,13 +248,20 @@ private ListenableFuture<Void> downloadBlob(
   /** A reporter that reports download progresses. */
   public static class DownloadProgressReporter {
     private static final Pattern PATTERN = Pattern.compile("^bazel-out/[^/]+/[^/]+/");
+    private final boolean includeFile;
     private final ProgressStatusListener listener;
     private final String id;
     private final String file;
     private final String totalSize;
     private final AtomicLong downloadedBytes = new AtomicLong(0);
 
     public DownloadProgressReporter(ProgressStatusListener listener, String file, long totalSize) {
+      this(/* includeFile= */ true, listener, file, totalSize);
+    }
+
+    public DownloadProgressReporter(
+        boolean includeFile, ProgressStatusListener listener, String file, long totalSize) {
+      this.includeFile = includeFile;
       this.listener = listener;
       this.id = file;
       this.totalSize = bytesCountToDisplayString(totalSize);
@@ -279,12 +286,21 @@ void finished() {
     private void reportProgress(boolean includeBytes, boolean finished) {
       String progress;
       if (includeBytes) {
-        progress =
-            String.format(
-                "Downloading %s, %s / %s",
-                file, bytesCountToDisplayString(downloadedBytes.get()), totalSize);
+        if (includeFile) {
+          progress =
+              String.format(
+                  "Downloading %s, %s / %s",
+                  file, bytesCountToDisplayString(downloadedBytes.get()), totalSize);
+        } else {
+          progress =
+              String.format("%s / %s", bytesCountToDisplayString(downloadedBytes.get()), totalSize);
+        }
       } else {
-        progress = String.format("Downloading %s", file);
+        if (includeFile) {
+          progress = String.format("Downloading %s", file);
+        } else {
+          progress = "";
+        }
       }
       listener.onProgressStatus(SpawnProgressEvent.create(id, progress, finished));
     }

src/main/java/com/google/devtools/build/lib/remote/common/ProgressStatusListener.java

@@ -13,13 +13,14 @@
 // limitations under the License.
 package com.google.devtools.build.lib.remote.common;
 
+import com.google.devtools.build.lib.exec.SpawnProgressEvent;
 import com.google.devtools.build.lib.exec.SpawnRunner.ProgressStatus;
 
 /** An interface that is used to receive {@link ProgressStatus} updates during spawn execution. */
 @FunctionalInterface
 public interface ProgressStatusListener {
 
-  void onProgressStatus(ProgressStatus progress);
+  void onProgressStatus(SpawnProgressEvent progress);
 
   /** A {@link ProgressStatusListener} that does nothing. */
   ProgressStatusListener NO_ACTION =

src/main/java/com/google/devtools/build/lib/runtime/UiStateTracker.java

@@ -993,7 +993,8 @@ synchronized boolean hasActivities() {
     return !(buildCompleted()
         && bepOpenTransports.isEmpty()
         && activeActionUploads.get() == 0
-        && activeActionDownloads.get() == 0);
+        && activeActionDownloads.get() == 0
+        && runningDownloads.isEmpty());
   }
 
   /**
@@ -1106,7 +1107,8 @@ private void reportOnOneDownload(
     terminalWriter.append(url + postfix);
   }
 
-  protected void reportOnDownloads(AnsiTerminalWriter terminalWriter) throws IOException {
+  protected void reportOnDownloads(PositionAwareAnsiTerminalWriter terminalWriter)
+      throws IOException {
     int count = 0;
     long nanoTime = clock.nanoTime();
     int downloadCount = runningDownloads.size();
@@ -1116,7 +1118,10 @@ protected void reportOnDownloads(AnsiTerminalWriter terminalWriter) throws IOExc
         break;
       }
       count++;
-      terminalWriter.newline().append(FETCH_PREFIX);
+      if (terminalWriter.getPosition() != 0) {
+        terminalWriter.newline();
+      }
+      terminalWriter.append(FETCH_PREFIX);
       reportOnOneDownload(
           url,
           nanoTime,

src/test/java/com/google/devtools/build/lib/remote/ActionInputPrefetcherTestBase.java

@@ -173,7 +173,7 @@ public void prefetchFiles_fileExists_doNotDownload()
 
     wait(prefetcher.prefetchFiles(metadata.keySet(), metadataProvider));
 
-    verify(prefetcher, never()).doDownloadFile(any(), any(), any(), any());
+    verify(prefetcher, never()).doDownloadFile(any(), any(), any(), any(), any());
     assertThat(prefetcher.downloadedFiles()).containsExactly(a.getPath());
     assertThat(prefetcher.downloadsInProgress()).isEmpty();
   }
@@ -190,7 +190,7 @@ public void prefetchFiles_fileExistsButContentMismatches_download()
 
     wait(prefetcher.prefetchFiles(metadata.keySet(), metadataProvider));
 
-    verify(prefetcher).doDownloadFile(any(), eq(a.getExecPath()), any(), any());
+    verify(prefetcher).doDownloadFile(any(), any(), eq(a.getExecPath()), any(), any());
     assertThat(prefetcher.downloadedFiles()).containsExactly(a.getPath());
     assertThat(prefetcher.downloadsInProgress()).isEmpty();
     assertThat(FileSystemUtils.readContent(a.getPath(), UTF_8)).isEqualTo("hello world remote");
@@ -531,8 +531,8 @@ protected static void mockDownload(
       throws IOException {
     doAnswer(
             invocation -> {
-              Path path = invocation.getArgument(0);
-              FileArtifactValue metadata = invocation.getArgument(2);
+              Path path = invocation.getArgument(1);
+              FileArtifactValue metadata = invocation.getArgument(3);
               byte[] content = cas.get(HashCode.fromBytes(metadata.getDigest()));
               if (content == null) {
                 return Futures.immediateFailedFuture(new IOException("Not found"));
@@ -541,7 +541,7 @@ protected static void mockDownload(
               return resultSupplier.get();
             })
         .when(prefetcher)
-        .doDownloadFile(any(), any(), any(), any());
+        .doDownloadFile(any(), any(), any(), any(), any());
   }
 
   private void assertReadableNonWritableAndExecutable(Path path) throws IOException {