This directory contains support for building the Fuchsia tree with build actions running on RBE (remote build execution).

Remote execution wrappers

The top-level remote execution wrappers are used as command prefixes:

  • cxx_remote_wrapper.py: prefix wrapper for remote compiling C++
  • rustc_remote_wrapper.py: prefix wrapper for remote compiling Rust
    • Detects and gathers all inputs and tools needed for remote compiling.
    • Detects extra outputs to download produced by remote compiling.
  • remote_action.py: prefix wrapper for generic remote actions
    • Exists as standalone wrapper and library.
    • Includes detailed diagnostics for certain error conditions.
    • Includes limited fault-tolerance and retries.
    • The C++ and Rust wrappers inherit all of the features of this generic script.
  • fuchsia-reproxy-wrap.sh: automatically start/shutdown reproxy (needed by rewrapper) around any command. Used by fx build.

More details can be found by running with --help.

Support scripts

  • cl_utils.py: generic command-line operation library
  • cxx.py: for understanding structure of C/C++ compile commands
  • fuchsia.py: Fuchsia-tree specific directory layouts and conventions. Parties interested in re-using wrapper scripts found here should expect to replace this file.
  • output_leak_scanner.py: Check that commands and outputs do not leak the name of the build output directory, for better caching outcomes.
  • relativize_args.py: Attempt to transform commands with absolute paths into equivalent commands with relative paths. This can be useful for build systems that insist on absolute paths, like cmake.
  • rustc.py: for understanding structure of rustc compile commands

Configurations

  • fuchsia-rewrapper.cfg: rewrapper configuration
  • fuchsia-reproxy.cfg: reproxy configuration

Troubleshooting tools

  • action_diff.sh: recursively queries through two reproxy logs to root-cause differences between output and intermediate artifacts. This is useful for examining unexpected digest differences and cache misses.
  • bbtool.py: buildbucket related tools
    • fetch_reproxy_log: retrieve .rrpl log, possibly from subbuild.
  • bb_fetch_rbe_cas.sh: retrieve a remote-built artifact from the RBE CAS using a buildbucket id and the path under the build output directory.
  • detail-diff.sh: attempts to compare human-readable representations of files, including some binary files, by using tools like objdump.
  • remotetool.sh: can lookup actions and artifacts in the RBE CAS. From: https://github.com/bazelbuild/remote-apis-sdks
  • reproxy_logs.sh: subcommand utility
    • diff: report meaningful difference between two reproxy logs
    • output_file_digest: lookup the digest of a remote built artifact
    • bandwidth: report total download and upload bytes from reproxy log
    • plot_download: plot download demand over the course of a build
  • rpl_tool.sh: tools that involve reproxy logs and remotetool together
    • expand_to_rpl: populate .rrpl with command and inputs -> .rpl

All tools have more detailed usage with --help.

GN files

  • build/toolchain/rbe.gni: global args.gn variables for RBE

  • build/toolchain/clang_toolchain.gni: uses RBE wrappers depending on configuration

  • build/rust/rustc_*.gni: uses RBE wrappers depending on configuration

Metrics and logs

  • upload_reproxy_logs.py: pushes RBE metrics and detailed logs to BigQuery.

    • This can be enabled by fx build-metrics.

  • pb_message_util.py: library for translating protobufs to JSON