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

// Copyright 2023 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.exec;

import static com.google.common.base.Preconditions.checkState;
import static com.google.devtools.build.lib.exec.SpawnLogContext.computeDigest;
import static com.google.devtools.build.lib.exec.SpawnLogContext.getEnvironmentVariables;
import static com.google.devtools.build.lib.exec.SpawnLogContext.getPlatform;
import static com.google.devtools.build.lib.exec.SpawnLogContext.getSpawnMetricsProto;

import com.google.common.collect.ImmutableList;
import com.google.devtools.build.lib.actions.ActionInput;
import com.google.devtools.build.lib.actions.Artifact;
import com.google.devtools.build.lib.actions.CommandLines.ParamFileActionInput;
import com.google.devtools.build.lib.actions.ExecException;
import com.google.devtools.build.lib.actions.InputMetadataProvider;
import com.google.devtools.build.lib.actions.RunfilesSupplier.RunfilesTree;
import com.google.devtools.build.lib.actions.Spawn;
import com.google.devtools.build.lib.actions.SpawnResult;
import com.google.devtools.build.lib.actions.Spawns;
import com.google.devtools.build.lib.actions.cache.VirtualActionInput;
import com.google.devtools.build.lib.collect.nestedset.NestedSet;
import com.google.devtools.build.lib.exec.Protos.Digest;
import com.google.devtools.build.lib.exec.Protos.ExecLogEntry;
import com.google.devtools.build.lib.exec.Protos.Platform;
import com.google.devtools.build.lib.profiler.Profiler;
import com.google.devtools.build.lib.profiler.SilentCloseable;
import com.google.devtools.build.lib.remote.options.RemoteOptions;
import com.google.devtools.build.lib.util.io.AsynchronousMessageOutputStream;
import com.google.devtools.build.lib.util.io.MessageOutputStream;
import com.google.devtools.build.lib.vfs.DigestHashFunction;
import com.google.devtools.build.lib.vfs.FileSystem;
import com.google.devtools.build.lib.vfs.Path;
import com.google.devtools.build.lib.vfs.PathFragment;
import com.google.devtools.build.lib.vfs.XattrProvider;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import it.unimi.dsi.fastutil.objects.Object2IntOpenHashMap;
import java.io.IOException;
import java.time.Duration;
import java.util.ArrayDeque;
import java.util.Collection;
import java.util.Map;
import java.util.SortedMap;
import javax.annotation.Nullable;
import javax.annotation.concurrent.GuardedBy;

/** A {@link SpawnLogContext} implementation that produces a log in compact format. */
public class CompactSpawnLogContext implements SpawnLogContext {

  private interface ExecLogEntrySupplier {
    ExecLogEntry.Builder get() throws IOException;
  }

  private final PathFragment execRoot;
  @Nullable private final RemoteOptions remoteOptions;
  private final DigestHashFunction digestHashFunction;
  private final XattrProvider xattrProvider;

  // Maps a key identifying an entry into its ID.
  // Each key is either a NestedSet.Node or the String path of a file or directory.
  // Only entries that are likely to be referenced by future entries are stored.
  // Use a specialized map for minimal memory footprint.
  @GuardedBy("this")
  private final Object2IntOpenHashMap<Object> entryMap = new Object2IntOpenHashMap<>();

  // The next available entry ID.
  @GuardedBy("this")
  int nextEntryId = 1;

  // Output stream to write to.
  private final MessageOutputStream<ExecLogEntry> outputStream;

  public CompactSpawnLogContext(
      Path outputPath,
      PathFragment execRoot,
      @Nullable RemoteOptions remoteOptions,
      DigestHashFunction digestHashFunction,
      XattrProvider xattrProvider)
      throws IOException {
    this.execRoot = execRoot;
    this.remoteOptions = remoteOptions;
    this.digestHashFunction = digestHashFunction;
    this.xattrProvider = xattrProvider;
    this.outputStream = getOutputStream(outputPath);
  }

  private static MessageOutputStream<ExecLogEntry> getOutputStream(Path path) throws IOException {
    // Use an AsynchronousMessageOutputStream so that writes occur in a separate thread.
    // This ensures concurrent writes don't tear and avoids blocking execution.
    return new AsynchronousMessageOutputStream<>(path);
  }

  @Override
  public void logSpawn(
      Spawn spawn,
      InputMetadataProvider inputMetadataProvider,
      SortedMap<PathFragment, ActionInput> inputMap,
      FileSystem fileSystem,
      Duration timeout,
      SpawnResult result)
      throws IOException, ExecException {
    try (SilentCloseable c = Profiler.instance().profile("logSpawn")) {
      ExecLogEntry.Spawn.Builder builder = ExecLogEntry.Spawn.newBuilder();

      builder.addAllArgs(spawn.getArguments());
      builder.addAllEnvVars(getEnvironmentVariables(spawn));
      Platform platform = getPlatform(spawn, remoteOptions);
      if (platform != null) {
        builder.setPlatform(platform);
      }

      builder.setInputSetId(logInputs(spawn, inputMetadataProvider, fileSystem));
      builder.setToolSetId(logTools(spawn, inputMetadataProvider, fileSystem));

      builder.setTargetLabel(spawn.getTargetLabel().getCanonicalForm());
      builder.setMnemonic(spawn.getMnemonic());

      for (ActionInput output : spawn.getOutputFiles()) {
        Path path = fileSystem.getPath(execRoot.getRelative(output.getExecPath()));
        if (!path.exists()) {
          builder.addOutputs(
              ExecLogEntry.Output.newBuilder().setMissingPath(output.getExecPathString()));
        } else if (path.isDirectory()) {
          builder.addOutputs(
              ExecLogEntry.Output.newBuilder()
                  .setDirectoryId(logDirectory(output, path, inputMetadataProvider)));
        } else {
          builder.addOutputs(
              ExecLogEntry.Output.newBuilder()
                  .setFileId(logFile(output, path, inputMetadataProvider)));
        }
      }

      builder.setExitCode(result.exitCode());
      if (result.status() != SpawnResult.Status.SUCCESS) {
        builder.setStatus(result.status().toString());
      }
      builder.setRunner(result.getRunnerName());
      builder.setCacheHit(result.isCacheHit());
      builder.setRemotable(Spawns.mayBeExecutedRemotely(spawn));
      builder.setCacheable(Spawns.mayBeCached(spawn));
      builder.setRemoteCacheable(Spawns.mayBeCachedRemotely(spawn));

      if (result.getDigest() != null) {
        builder.setDigest(result.getDigest().getHash());
      }

      builder.setTimeoutMillis(timeout.toMillis());
      builder.setMetrics(getSpawnMetricsProto(result));

      try (SilentCloseable c1 = Profiler.instance().profile("logEntry")) {
        logEntry(null, () -> ExecLogEntry.newBuilder().setSpawn(builder));
      }
    }
  }

  /**
   * Logs the inputs.
   *
   * @return the entry ID of the {@link ExecLogEntry.Set} describing the inputs, or 0 if there are
   *     no inputs.
   */
  private int logInputs(
      Spawn spawn, InputMetadataProvider inputMetadataProvider, FileSystem fileSystem)
      throws IOException {

    // Add runfiles and filesets as additional direct members of the top-level nested set of inputs.
    // This prevents it from being shared, but experimentally, the top-level input nested set for a
    // spawn is almost never a transitive member of other nested sets, and not recording its entry
    // ID turns out to be a very significant memory optimization.

    ImmutableList.Builder<Integer> additionalDirectoryIds = ImmutableList.builder();

    for (RunfilesTree tree : spawn.getRunfilesSupplier().getRunfilesTrees()) {
      // The runfiles symlink tree might not have been materialized on disk, so use the mapping.
      additionalDirectoryIds.add(
          logRunfilesDirectory(
              tree.getExecPath(), tree.getMapping(), inputMetadataProvider, fileSystem));
    }

    for (Artifact fileset : spawn.getFilesetMappings().keySet()) {
      // The fileset symlink tree is always materialized on disk.
      additionalDirectoryIds.add(
          logDirectory(
              fileset,
              fileSystem.getPath(execRoot.getRelative(fileset.getExecPath())),
              inputMetadataProvider));
    }

    return logNestedSet(
        spawn.getInputFiles(),
        additionalDirectoryIds.build(),
        inputMetadataProvider,
        fileSystem,
        /* shared= */ false);
  }

  /**
   * Logs the tool inputs.
   *
   * @return the entry ID of the {@link ExecLogEntry.Set} describing the tool inputs, or 0 if there
   *     are no tool inputs.
   */
  private int logTools(
      Spawn spawn, InputMetadataProvider inputMetadataProvider, FileSystem fileSystem)
      throws IOException {
    return logNestedSet(
        spawn.getToolFiles(),
        ImmutableList.of(),
        inputMetadataProvider,
        fileSystem,
        /* shared= */ true);
  }

  /**
   * Logs a nested set.
   *
   * @param set the nested set
   * @param additionalDirectoryIds the entry IDs of additional {@link ExecLogEntry.Directory}
   *     entries to include as direct members
   * @param shared whether this nested set is likely to be a transitive member of other sets
   * @return the entry ID of the {@link ExecLogEntry.InputSet} describing the nested set, or 0 if
   *     the nested set is empty.
   */
  private int logNestedSet(
      NestedSet<? extends ActionInput> set,
      Collection<Integer> additionalDirectoryIds,
      InputMetadataProvider inputMetadataProvider,
      FileSystem fileSystem,
      boolean shared)
      throws IOException {
    if (set.isEmpty() && additionalDirectoryIds.isEmpty()) {
      return 0;
    }

    return logEntry(
        shared ? set.toNode() : null,
        () -> {
          ExecLogEntry.InputSet.Builder builder =
              ExecLogEntry.InputSet.newBuilder().addAllDirectoryIds(additionalDirectoryIds);

          for (NestedSet<? extends ActionInput> transitive : set.getNonLeaves()) {
            checkState(!transitive.isEmpty());
            builder.addTransitiveSetIds(
                logNestedSet(
                    transitive,
                    /* additionalDirectoryIds= */ ImmutableList.of(),
                    inputMetadataProvider,
                    fileSystem,
                    /* shared= */ true));
          }

          for (ActionInput input : set.getLeaves()) {
            // Runfiles are logged separately.
            if (input instanceof Artifact && ((Artifact) input).isMiddlemanArtifact()) {
              continue;
            }
            // Filesets are logged separately.
            if (input instanceof Artifact && ((Artifact) input).isFileset()) {
              continue;
            }
            Path path = fileSystem.getPath(execRoot.getRelative(input.getExecPath()));
            if (path.isDirectory()) {
              builder.addDirectoryIds(logDirectory(input, path, inputMetadataProvider));
            } else {
              builder.addFileIds(logFile(input, path, inputMetadataProvider));
            }
          }

          return ExecLogEntry.newBuilder().setInputSet(builder);
        });
  }

  /**
   * Logs a file.
   *
   * @param input the input representing the file.
   * @param path the path to the file
   * @return the entry ID of the {@link ExecLogEntry.File} describing the file.
   */
  private int logFile(ActionInput input, Path path, InputMetadataProvider inputMetadataProvider)
      throws IOException {
    checkState(!(input instanceof VirtualActionInput.EmptyActionInput));

    return logEntry(
        // A ParamFileActionInput is never shared between spawns.
        input instanceof ParamFileActionInput ? null : input.getExecPathString(),
        () -> {
          ExecLogEntry.File.Builder builder = ExecLogEntry.File.newBuilder();

          builder.setPath(input.getExecPathString());

          Digest digest =
              computeDigest(input, path, inputMetadataProvider, xattrProvider, digestHashFunction);
          builder.setDigest(digest.getHash());
          builder.setSizeBytes(digest.getSizeBytes());

          return ExecLogEntry.newBuilder().setFile(builder);
        });
  }

  /**
   * Logs a directory.
   *
   * <p>This may be either a source directory, a fileset or an output directory. An output directory
   * is not guaranteed to be a tree artifact; we must support the case where a directory is produced
   * when a file was expected. For runfiles, {@link #logRunfilesDirectory} must be used instead.
   *
   * @param input the input representing the directory
   * @param root the path to the directory
   * @return the entry ID of the {@link ExecLogEntry.Directory} describing the directory.
   */
  private int logDirectory(
      ActionInput input, Path root, InputMetadataProvider inputMetadataProvider)
      throws IOException {
    return logEntry(
        input.getExecPathString(),
        () ->
            ExecLogEntry.newBuilder()
                .setDirectory(
                    ExecLogEntry.Directory.newBuilder()
                        .setPath(input.getExecPathString())
                        .addAllFiles(
                            expandDirectory(root, /* pathPrefix= */ null, inputMetadataProvider))));
  }

  /**
   * Logs a runfiles directory.
   *
   * <p>We can't use {@link #logDirectory} because the runfiles symlink tree might not have been
   * materialized on disk. We must follow the mappings to the actual location of the artifacts.
   *
   * @param root the path to the runfiles directory
   * @param mapping a map from runfiles-relative path to the underlying artifact, or null for an
   *     empty file
   * @return the entry ID of the {@link ExecLogEntry.Directory} describing the directory.
   */
  private int logRunfilesDirectory(
      PathFragment root,
      Map<PathFragment, Artifact> mapping,
      InputMetadataProvider inputMetadataProvider,
      FileSystem fileSystem)
      throws IOException {
    return logEntry(
        root.getPathString(),
        () -> {
          ExecLogEntry.Directory.Builder builder =
              ExecLogEntry.Directory.newBuilder().setPath(root.getPathString());

          for (Map.Entry<PathFragment, Artifact> entry : mapping.entrySet()) {
            String runfilesPath = entry.getKey().getPathString();
            Artifact input = entry.getValue();

            if (input == null) {
              // Empty file.
              builder.addFiles(ExecLogEntry.File.newBuilder().setPath(runfilesPath));
              continue;
            }

            Path path = fileSystem.getPath(execRoot.getRelative(input.getExecPath()));

            if (path.isDirectory()) {
              builder.addAllFiles(expandDirectory(path, runfilesPath, inputMetadataProvider));
              continue;
            }

            Digest digest =
                computeDigest(
                    input, path, inputMetadataProvider, xattrProvider, digestHashFunction);

            builder.addFiles(
                ExecLogEntry.File.newBuilder()
                    .setPath(runfilesPath)
                    .setSizeBytes(digest.getSizeBytes())
                    .setDigest(digest.getHash()));
          }

          return ExecLogEntry.newBuilder().setDirectory(builder);
        });
  }

  /**
   * Expands a directory.
   *
   * @param root the path to the directory
   * @param pathPrefix a prefix to prepend to each child path
   * @return the list of files transitively contained in the directory
   */
  private ImmutableList<ExecLogEntry.File> expandDirectory(
      Path root, @Nullable String pathPrefix, InputMetadataProvider inputMetadataProvider)
      throws IOException {
    ImmutableList.Builder<ExecLogEntry.File> builder = ImmutableList.builder();

    ArrayDeque<Path> dirs = new ArrayDeque<>();
    dirs.add(root);

    while (!dirs.isEmpty()) {
      Path dir = dirs.removeFirst();
      for (Path child : dir.getDirectoryEntries()) {
        if (child.isDirectory()) {
          dirs.addLast(child);
          continue;
        }

        String childPath = pathPrefix != null ? pathPrefix + "/" : "";
        childPath += child.relativeTo(root).getPathString();

        Digest digest =
            computeDigest(
                /* input= */ null, child, inputMetadataProvider, xattrProvider, digestHashFunction);

        builder.add(
            ExecLogEntry.File.newBuilder()
                .setPath(childPath)
                .setSizeBytes(digest.getSizeBytes())
                .setDigest(digest.getHash())
                .build());
      }
    }
    return builder.build();
  }

  /**
   * Ensures an entry is written to the log and returns its assigned ID.
   *
   * <p>If an entry with the same non-null key was previously added to the log, its recorded ID is
   * returned. Otherwise, the entry is computed, assigned an ID, and written to the log.
   *
   * @param key the key, or null if the ID shouldn't be recorded
   * @param supplier called to compute the entry; may cause other entries to be logged
   * @return the entry ID
   */
  @CanIgnoreReturnValue
  private synchronized int logEntry(@Nullable Object key, ExecLogEntrySupplier supplier)
      throws IOException {
    try (SilentCloseable c = Profiler.instance().profile("logEntry/synchronized")) {
      if (key == null) {
        // No need to check for a previously added entry.
        int id = nextEntryId++;
        outputStream.write(supplier.get().setId(id).build());
        return id;
      }

      checkState(key instanceof NestedSet.Node || key instanceof String);

      // Check for a previously added entry.
      int id = entryMap.getOrDefault(key, 0);
      if (id != 0) {
        return id;
      }

      // Compute a fresh entry and log it.
      // The following order of operations is crucial to ensure that this entry is preceded by any
      // entries it references, which in turn ensures the log can be parsed in a single pass.
      ExecLogEntry.Builder entry = supplier.get();
      id = nextEntryId++;
      entryMap.put(key, id);
      outputStream.write(entry.setId(id).build());
      return id;
    }
  }

  @Override
  public void close() throws IOException {
    outputStream.close();
  }
}