输出目录布局

本页将介绍输出目录的要求和布局。

要求

输出目录布局的要求:

  • 如果多个用户在同一个 Box 上进行构建,则不会发生冲突。
  • 支持同时在多个工作区中进行构建。
  • 支持在同一工作区中针对多个目标配置进行构建。
  • 不会与任何其他工具冲突。
  • 易于访问。
  • 易于清洁,甚至可以选择性地清理。
  • 清晰明确,即使用户在切换到其客户端目录时依赖符号链接也是如此。
  • 每个用户的所有构建状态都应位于一个目录下(“我想清理所有客户端中的所有 .o 文件。”)

当前布局

目前实现的解决方案:

  • 必须从包含 WORKSPACE 文件的目录(“工作区目录”)或其子目录中调用 Bazel。否则,它会报告错误。
  • outputRoot 在 Linux 上默认为 ~/.cache/bazel、macOS 上为 /private/var/tmp;在 Windows 上,该目录默认为 %HOME%(如果已设置),否则为 %USERPROFILE%(如果已设置),否则为设置了 FOLDERID_Profile 标志的调用 SHGetKnownFolderPath() 的结果。如在 Bazel 本身测试中一样,设置了环境变量 $TEST_TMPDIR,则该值将替换默认值。
  • Bazel 用户的构建状态位于 outputRoot/_bazel_$USER 下方。这称为 outputUserRoot 目录。
  • outputUserRoot 目录下面有一个 install 目录,其中包含一个 installBase 目录,其名称是 Bazel 安装清单的 MD5 哈希。
  • outputUserRoot 目录下方,还会创建一个 outputBase 目录,其名称是工作区目录路径名的 MD5 哈希值。例如,如果 Bazel 在工作区目录 /home/user/src/my-project(或指向该目录的符号链接)中运行,系统会创建一个名为 /home/user/.cache/bazel/_bazel_user/7ffd56a6e4cb724ea575aba15733d113 的输出基本目录。
  • 您可以使用 Bazel 的 --output_base 启动选项来替换默认输出基本目录。例如 bazel --output_base=/tmp/bazel/output build x/y:z
  • 您还可以使用 Bazel 的 --output_user_root 启动选项来替换默认安装基础和输出基本目录。例如:bazel --output_user_root=/tmp/bazel build x/y:z

“bazel-<workspace-name>”“bazel-out”“bazel-testlogs”和“bazel-bin”的符号链接放在工作区目录中;这些符号链接指向输出目录内某个目标专用目录中的某些目录。这些符号链接只是为了方便用户,因为 Bazel 本身并不使用这些符号链接。此外,仅当工作区目录可写入时,才会执行此操作。

布局图

目录布局如下:

<workspace-name>/                         <== The workspace directory
  bazel-my-project => <...my-project>     <== Symlink to execRoot
  bazel-out => <...bin>                   <== Convenience symlink to outputPath
  bazel-bin => <...bin>                   <== Convenience symlink to most recent written bin dir $(BINDIR)
  bazel-testlogs => <...testlogs>         <== Convenience symlink to the test logs directory

/home/user/.cache/bazel/                  <== Root for all Bazel output on a machine: outputRoot
  _bazel_$USER/                           <== Top level directory for a given user depends on the user name:
                                              outputUserRoot
    install/
      fba9a2c87ee9589d72889caf082f1029/   <== Hash of the Bazel install manifest: installBase
        _embedded_binaries/               <== Contains binaries and scripts unpacked from the data section of
                                              the bazel executable on first run (such as helper scripts and the
                                              main Java file BazelServer_deploy.jar)
    7ffd56a6e4cb724ea575aba15733d113/     <== Hash of the client's workspace directory (such as
                                              /home/some-user/src/my-project): outputBase
      action_cache/                       <== Action cache directory hierarchy
                                              This contains the persistent record of the file
                                              metadata (timestamps, and perhaps eventually also MD5
                                              sums) used by the FilesystemValueChecker.
      action_outs/                        <== Action output directory. This contains a file with the
                                              stdout/stderr for every action from the most recent
                                              bazel run that produced output.
      command.log                         <== A copy of the stdout/stderr output from the most
                                              recent bazel command.
      external/                           <== The directory that remote repositories are
                                              downloaded/symlinked into.
      server/                             <== The Bazel server puts all server-related files (such
                                              as socket file, logs, etc) here.
        jvm.out                           <== The debugging output for the server.
      execroot/                           <== The working directory for all actions. For special
                                              cases such as sandboxing and remote execution, the
                                              actions run in a directory that mimics execroot.
                                              Implementation details, such as where the directories
                                              are created, are intentionally hidden from the action.
                                              All actions can access its inputs and outputs relative
                                              to the execroot directory.
        <workspace-name>/                 <== Working tree for the Bazel build & root of symlink forest: execRoot
          _bin/                           <== Helper tools are linked from or copied to here.

          bazel-out/                      <== All actual output of the build is under here: outputPath
            local_linux-fastbuild/        <== one subdirectory per unique target BuildConfiguration instance;
                                              this is currently encoded
              bin/                        <== Bazel outputs binaries for target configuration here: $(BINDIR)
                foo/bar/_objs/baz/        <== Object files for a cc_* rule named //foo/bar:baz
                  foo/bar/baz1.o          <== Object files from source //foo/bar:baz1.cc
                  other_package/other.o   <== Object files from source //other_package:other.cc
                foo/bar/baz               <== foo/bar/baz might be the artifact generated by a cc_binary named
                                              //foo/bar:baz
                foo/bar/baz.runfiles/     <== The runfiles symlink farm for the //foo/bar:baz executable.
                  MANIFEST
                  <workspace-name>/
                    ...
              genfiles/                   <== Bazel puts generated source for the target configuration here:
                                              $(GENDIR)
                foo/bar.h                     such as foo/bar.h might be a headerfile generated by //foo:bargen
              testlogs/                   <== Bazel internal test runner puts test log files here
                foo/bartest.log               such as foo/bar.log might be an output of the //foo:bartest test with
                foo/bartest.status            foo/bartest.status containing exit status of the test (such as
                                              PASSED or FAILED (Exit 1), etc)
              include/                    <== a tree with include symlinks, generated as needed. The
                                              bazel-include symlinks point to here. This is used for
                                              linkstamp stuff, etc.
            host/                         <== BuildConfiguration for build host (user's workstation), for
                                              building prerequisite tools, that will be used in later stages
                                              of the build (ex: Protocol Compiler)
        <packages>/                       <== Packages referenced in the build appear as if under a regular workspace

*.runfiles 目录的布局在 RunfilesSupport 指向的位置中有详细记录。

bazel clean

bazel clean 会对 outputPathaction_cache 目录执行 rm -rf。它还会移除工作区符号链接。--expunge 选项将清理整个 outputBase。