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:

• reclient_cxx.sh: prefix wrapper for remote compiling C++
  • cxx_remote_wrapper.py: is a similar heavier wrapper with additional features and workarounds.
• rustc_remote_wrapper.py: prefix wrapper for remote compiling and linking Rust
  • Detects and gathers all inputs and tools needed for remote compiling.
  • Detects extra outputs to download produced by remote compiling.
• cxx_link_remote_wrapper.py: prefix wrapper for remote ilnking C++
• prebuilt_tool_remote_wrapper.py: prefix wrapper for simple tools
• 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.
• dlwrap.py: downloads artifacts from RBE's CAS using download stub files

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
• tablefmt.py: utilities for printing readable ASCII tables
• textpb.py: generic protobuf text parsing library

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 and build/toolchain/zircon/zircon_toolchain.gni: use RBE wrappers depending on configuration

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

Metrics and logs

• build_summary.py: If your environment sets FX_BUILD_RBE_STATS=1, this script will be run after each build and display a summary of cache and download metrics.
• 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