| // Copyright 2021 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.analysis.actions; |
| |
| import com.google.common.collect.ImmutableList; |
| import com.google.devtools.build.lib.actions.Action; |
| import com.google.devtools.build.lib.actions.ActionInput; |
| import com.google.devtools.build.lib.actions.Artifact.DerivedArtifact; |
| import com.google.devtools.build.lib.actions.CommandLineItem; |
| import com.google.devtools.build.lib.actions.CommandLineItem.ExceptionlessMapFn; |
| import com.google.devtools.build.lib.actions.CommandLineItem.MapFn; |
| import com.google.devtools.build.lib.actions.CommandLines.ParamFileActionInput; |
| import com.google.devtools.build.lib.actions.PathMapper; |
| import com.google.devtools.build.lib.actions.Spawn; |
| import com.google.devtools.build.lib.analysis.config.CoreOptions.OutputPathsMode; |
| import com.google.devtools.build.lib.collect.nestedset.NestedSet; |
| import com.google.devtools.build.lib.vfs.PathFragment; |
| import java.util.HashSet; |
| import java.util.List; |
| import java.util.Objects; |
| import java.util.Optional; |
| import java.util.regex.Pattern; |
| import javax.annotation.Nullable; |
| |
| /** |
| * Main logic for experimental config-stripped execution paths: |
| * https://github.com/bazelbuild/bazel/issues/6526. |
| * |
| * <p>The actions executors run look like: {@code tool_pkg/mytool src/source.file |
| * bazel-out/x86-opt/pkg/gen.file -o bazel-out/x86-opt/pkg/myout}. |
| * |
| * <p>The "x86-opt" part is a path's "configuration prefix": information describing the build |
| * configuration of the action creating the artifact. This example shows artifacts created with |
| * {@code --cpu=x86 --compilation_mode=opt}. |
| * |
| * <p>Executors cache actions based on their a) command line, b) input and output paths, c) input |
| * digests. Configuration prefixes harm caching because even if an action behaves exactly the same |
| * for different CPU architectures, {@code <cpu>-opt} guarantees the paths will differ. |
| * |
| * <p>Config-stripping is an experimental feature that strips the configuration prefix from |
| * qualifying actions before running them, thus improving caching. "Qualifying" actions are actions |
| * known not to depend on the names of their input and output paths. Non-qualifying actions include |
| * manifest generators and compilers that store debug symbol source paths. |
| * |
| * <p>As an experimental feature, most logic is centralized here to provide easy hooks into executor |
| * and action code and avoid complicating large swaths of the code base. |
| * |
| * <p>Enable this feature by setting {@code --experimental_output_paths=strip}. This activates two |
| * effects: |
| * |
| * <ol> |
| * <li>"Qualifying" actions strip config paths from their command lines. An action qualifies if |
| * its implementation logic uses {@link PathMappers#create(Action, OutputPathsMode)} as |
| * described in its javadocs and has its mnemonic listed in {@link |
| * PathMappers#SUPPORTED_MNEMONICS}. Such an action must pass the {@link PathMapper} to all |
| * structured command line constructions. If any unstructured command line arguments refer to |
| * artifact paths, custom handling needs to be added to {@code mapCustomStarlarkArgv} or |
| * {@code getMapFn} below. |
| * <li>A supporting executor strips paths from qualifying actions' inputs and outputs before |
| * staging for execution by taking {@link Spawn#getPathMapper()} into account. |
| * </ol> |
| * |
| * <p>So an action is responsible for declaring that it strips paths and adjusting its command line |
| * accordingly. The executor is responsible for remapping action inputs and outputs to match. |
| */ |
| public final class StrippingPathMapper { |
| static final String GUID = "8eb2ad5a-85d4-435b-858f-5c192e91997d"; |
| |
| /** |
| * Creates a new {@link PathMapper} that strips config prefixes if the particular action instance |
| * supports it. |
| * |
| * @param action the action to potentially strip paths from |
| * @return a {@link StrippingPathMapper} if the action supports it, else {@link Optional#empty()}. |
| */ |
| static Optional<PathMapper> tryCreate(Action action) { |
| // This is expected to always be "bazel-out", but we don't want to hardcode it here. |
| PathFragment outputRoot = action.getPrimaryOutput().getExecPath().subFragment(0, 1); |
| if (isPathStrippable(action.getInputs(), outputRoot)) { |
| return Optional.of( |
| create(action.getMnemonic(), action instanceof StarlarkAction, outputRoot)); |
| } |
| return Optional.empty(); |
| } |
| |
| private static PathMapper create( |
| String mnemonic, boolean isStarlarkAction, PathFragment outputRoot) { |
| final StringStripper argStripper = new StringStripper(outputRoot.getPathString()); |
| final ExceptionlessMapFn<Object> structuredArgStripper = |
| (object, args) -> { |
| if (object instanceof String) { |
| args.accept(argStripper.strip((String) object)); |
| } else { |
| args.accept(CommandLineItem.expandToCommandLine(object)); |
| } |
| }; |
| // This kind of special handling should not be extended. It is a hack that works around a |
| // limitation of the native implementation of location expansion: The output is just a list of |
| // strings, not a structured command line that would allow transparent path mapping. |
| // Instead, reimplement location expansion in Starlark and have it return an Args object. |
| final boolean isJavaAction = |
| mnemonic.equals("Javac") |
| || mnemonic.equals("JavacTurbine") |
| || mnemonic.equals("Turbine") |
| || mnemonic.equals("JavaResourceJar"); |
| return new PathMapper() { |
| @Override |
| public String getMappedExecPathString(ActionInput artifact) { |
| if (artifact instanceof DerivedArtifact || artifact instanceof ParamFileActionInput) { |
| return strip(artifact.getExecPath()).getPathString(); |
| } else { |
| return artifact.getExecPathString(); |
| } |
| } |
| |
| @Override |
| public PathFragment map(PathFragment execPath) { |
| return isOutputPath(execPath, outputRoot) ? strip(execPath) : execPath; |
| } |
| |
| @Override |
| public List<String> mapCustomStarlarkArgs(List<String> args) { |
| if (!isStarlarkAction) { |
| return args; |
| } |
| // Add your favorite Starlark mnemonic that needs custom arg processing here. |
| if (!mnemonic.contains("Android") |
| && !mnemonic.equals("MergeManifests") |
| && !mnemonic.equals("StarlarkRClassGenerator") |
| && !mnemonic.equals("StarlarkAARGenerator") |
| && !mnemonic.equals("JetifySrcs") |
| && !mnemonic.equals("Desugar")) { |
| return args; |
| } |
| // Add your favorite arg to custom-process here. When Bazel finds one of these in the |
| // argument list (an argument name), it strips output path prefixes from the following |
| // argument (the argument value). |
| ImmutableList<String> starlarkArgsToStrip = |
| ImmutableList.of( |
| "--mainData", |
| "--primaryData", |
| "--directData", |
| "--data", |
| "--resources", |
| "--mergeeManifests", |
| "--library", |
| "-i", |
| "--input"); |
| for (int i = 1; i < args.size(); i++) { |
| if (starlarkArgsToStrip.contains(args.get(i - 1))) { |
| args.set(i, argStripper.strip(args.get(i))); |
| } |
| } |
| return args; |
| } |
| |
| @Override |
| public ExceptionlessMapFn<Object> getMapFn(@Nullable String previousFlag) { |
| if (isJavaAction) { |
| if (Objects.equals(previousFlag, "--javacopts") |
| || Objects.equals(previousFlag, "--resources")) { |
| return structuredArgStripper; |
| } |
| } |
| return MapFn.DEFAULT; |
| } |
| }; |
| } |
| |
| /** Utility class to strip output path configuration prefixes from arbitrary strings. */ |
| private static class StringStripper { |
| private final Pattern pattern; |
| private final String outputRoot; |
| |
| public StringStripper(String outputRoot) { |
| this.outputRoot = outputRoot; |
| this.pattern = stripPathsPattern(outputRoot); |
| } |
| |
| /** |
| * Returns the regex to strip output paths from a string. |
| * |
| * <p>Supports strings with multiple output paths in arbitrary places. For example |
| * "/path/to/compiler bazel-out/x86-fastbuild/foo src/my.src -Dbazel-out/arm-opt/bar". |
| * |
| * <p>Doesn't strip paths that would be non-existent without config prefixes. For example, these |
| * are unchanged: "bazel-out/x86-fastbuild", "bazel-out;foo", "/path/to/compiler bazel-out". |
| * |
| * @param outputRoot root segment of output paths (e.g. "bazel-out") |
| */ |
| private static Pattern stripPathsPattern(String outputRoot) { |
| // Match "bazel-out" followed by a slash followed by any combination of word characters, "_", |
| // and "-", followed by another slash. This would miss substrings like |
| // "bazel-out/k8-fastbuild". But those don't represent actual outputs (all outputs would have |
| // to have names beneath that path). So we're not trying to replace those. |
| return Pattern.compile(outputRoot + "/[\\w_-]+/"); |
| } |
| |
| public String strip(String str) { |
| return pattern.matcher(str).replaceAll(outputRoot + "/"); |
| } |
| } |
| |
| /** |
| * Is this a strippable path? |
| * |
| * @param artifact artifact whose path to check |
| * @param outputRoot the output tree's execPath-relative root (e.g. "bazel-out") |
| */ |
| private static boolean isOutputPath(ActionInput artifact, PathFragment outputRoot) { |
| // We can't simply check for DerivedArtifact. Output paths can also appear, for example, in |
| // ParamFileActionInput and ActionInputHelper.BasicActionInput. |
| return isOutputPath(artifact.getExecPath(), outputRoot); |
| } |
| |
| /** Private utility method: Is this a strippable path? */ |
| private static boolean isOutputPath(PathFragment pathFragment, PathFragment outputRoot) { |
| return pathFragment.startsWith(outputRoot); |
| } |
| |
| /** |
| * Is this action safe to strip? |
| * |
| * <p>This is distinct from whether we <b>should</b> strip it. An action is stripped if a) the |
| * action is explicitly supported (see {@link PathMappers#SUPPORTED_MNEMONICS}) and b) it's safe |
| * to do that (for example, the action doesn't have two inputs in different configurations that |
| * would resolve to the same path if prefixes were removed). |
| * |
| * <p>This method checks b). |
| */ |
| private static boolean isPathStrippable( |
| NestedSet<? extends ActionInput> actionInputs, PathFragment outputRoot) { |
| // For qualifying action types, check that no inputs or outputs would clash if paths were |
| // removed, e.g. "bazel-out/k8-fastbuild/foo" and "bazel-out/host/foo". |
| // |
| // A more clever algorithm could remap these with custom prefixes - "bazel-out/1/foo" and |
| // "bazel-out/2/foo" - if experience shows that would help. |
| // |
| // Another approach could keep host paths intact (since the "host" path prefix doesn't vary |
| // with configurations). While this would help more action instances qualify, it also blocks |
| // caching the same action in host and target configurations. This could be mitigated by |
| // stripping the host prefix *only* when the entire action is in the host configuration. |
| HashSet<PathFragment> rootRelativePaths = new HashSet<>(); |
| for (ActionInput input : actionInputs.toList()) { |
| if (!isOutputPath(input, outputRoot)) { |
| continue; |
| } |
| // For "bazel-out/k8-fastbuild/foo/bar", get "foo/bar". |
| if (!rootRelativePaths.add(input.getExecPath().subFragment(2))) { |
| // TODO(bazel-team): don't fail on duplicate inputs, i.e. when the same exact exec path |
| // (including config prefix) is included twice. |
| return false; |
| } |
| } |
| return true; |
| } |
| |
| /* |
| * Strips the configuration prefix from an output artifact's exec path. |
| */ |
| private static PathFragment strip(PathFragment execPath) { |
| return execPath.subFragment(0, 1).getRelative(execPath.subFragment(2)); |
| } |
| |
| private StrippingPathMapper() {} |
| } |