Developing with Bazel

We’re partway through a migration of our build system to Bazel. Bazel is a modern build system with better performance characteristics and correctness guarantees than we currently have with make/go build. Today, you can perform most day-to-day CRDB dev tasks with Bazel rather than with make -- and for the few tasks that you can’t/don’t know how to do with Bazel, please ask a question or contribute a solution. The Bazel migration is actively in progress and we always accept contributions even for minor/QOL improvements.

NOTE: for specific debugging tips on:
- Build failures, see “How to ensure your code builds with Bazel”
- Test failures, see “How to ensure your tests can run in the Bazel sandbox”

Prerequisites

Follow the directions on "Getting and building CockroachDB from source" or "Building from source on macOS" to get your development environment set up. If you’ve installed everything you need for the make build, you should already have more than enough for the Bazel build – for example, you don’t actually need Golang installed to build with Bazel (the Bazel build will download Go toolchain bits as needed).

Note that you do need a full installation of XCode to build on macOS. (No, a command-line tools instance does not suffice.) If you’ve already installed a command-line tools instance as part of setting up Homebrew or other tools, switch to the full XCode instance and accept the XCode license agreement with:

sudo xcode-select -s /Applications/Xcode.app && sudo xcodebuild -license accept

Getting started

Introduction to dev

dev is a light wrapper around Bazel that is well-suited to specific CRDB development tasks. Properly, when we say dev, we’re referring to the Go binary whose source lives in cockroach/pkg/cmd/dev, side-by-side with the Cockroach source. At the top level of the repo there is a wrapper script also called dev whose only job is to build pkg/cmd/dev and then invoke it with the passed-in arguments. This means that you can always type ./dev to run the version of dev at the commit you’ve checked out, which is typically what you want to do.

Doctor, doctor

Before trying to build anything, run the following:

./dev doctor

If dev notices any issues with your system that might prevent you from being able to build, it will let you know and tell you how to fix it. Make sure to run dev doctor before you ask for help just in case it catches something you didn’t know about.

NOTE: dev will take a while to run the first time you execute it since it needs to build itself. Be patient.

First steps: building cockroach

Start by building cockroach-short as follows:

./dev build //pkg/cmd/cockroach-short

(Note: the first time you run ./dev, dev will need to build itself, so be patient ) ./dev build short also works as an alias. The first thing dev does is tell you what bazel command it’s running. Bazel will pretty-print build output to the terminal and assuming the build is successful, dev will symlink the binary to ./cockroach-short for you.

You can also build cockroach{ccl,oss}:

./dev build //pkg/cmd/cockroach //pkg/cmd/cockroach-oss

As above, ./dev build cockroach cockroach-oss works as alias.

Run ./dev help build for more information about what you can do with dev build. Note that you can pass additional arguments directly to bazel build by adding them after --:

# build "verbosely", outputting all commands as they are run
./dev build short -- -s

You can cross-compile with the --cross option, as in:

./dev build --cross

--cross takes an optional argument which is the platform to cross-compile to: --cross=linux, --cross=windows, --cross=macos. dev will symlink the built binaries into the artifacts directory in this case. Note that cross-building requires Docker. Cross-compiling should work on M1 Macs, but this support is experimental, so report issues if you should observe any.

For more debugging tips on building with Bazel, see “How to ensure your code builds with Bazel”

Running tests

Run ./dev test with the name of one or more packages to execute all tests from those packages:

./dev test pkg/sql/types

If the test passes, you’ll see a brief message indicating which tests were run and their status:

INFO: Elapsed time: 7.842s, Critical Path: 7.26s
INFO: 48 processes: 3 internal, 45 darwin-sandbox.
INFO: Build completed successfully, 48 total actions
//pkg/sql/types:types_test                                               PASSED in 0.7s

If the test doesn’t pass, Bazel will print the location of the test’s log file:

INFO: Elapsed time: 8.763s, Critical Path: 7.94s
INFO: 46 processes: 1 internal, 45 darwin-sandbox.
INFO: Build completed, 1 test FAILED, 46 total actions
//pkg/sql/types:types_test                                               FAILED in 1.5s
  /private/var/tmp/_bazel_ricky/be70b24e7357091e16c49d70921b7985/execroot/cockroach/bazel-out/darwin-fastbuild/testlogs/pkg/sql/types/types_test/test.log

You can examine that file to see the complete logs for the test.

Tips and tricks

• dev test has a --stress flag for running tests under stress.

• Next to the test.log file produced by your test, you can find a test.xml file. This file contains specific information on each test run and its status, as well as timing information.

• The -v argument to dev test will result in more verbose logging as well as more detailed information written to the test.xml.

• As with dev build, dev test allows you to pass additional arguments directly to Bazel by putting them after --: for example, dev test pkg/sql/types -- --verbose_failures --sandbox_debug.

• To get test results printed as tests are being run add -v -- --test_output streamed to the test command.

• For more tips on debugging test failures, see “How to ensure your tests can run in the Bazel sandbox”

Other tasks

# Run benchmarks for pkg/sql/parser
./dev bench pkg/sql/parser
# Open a container running the "bazelbuilder" image. Requires Docker.
./dev builder
# Generate code (run this before submitting your PR).
./dev generate
# Run lints (WARNING: not all lints work in Bazel yet)
./dev lint
# logic tests!
./dev testlogic --files=$FILES --subtests=$SUBTESTS --config=$CONFIG

dev vs. make

This is a (non-exhaustive) 1-to-1 mapping of dev commands to their make equivalents. Feel free to add to this

General dev tips

• Since ./dev always builds dev unconditionally before doing anything else, that means there will be a slight delay before your build or test actually begins. Due to caching this pause should never be too long, but if it’s annoying you or you’ve found a way to thrash the cache, you can do:

  ./dev build dev

  This will place a binary at bin/dev and if bin is in your PATH, you can then omit the leading ./. In this document we’ll always spell ./dev with the leading ./ to squash ambiguity and for ease of copy-pasting.

A (hopefully) fast and error proof dev workflow

TODO(a UI developer): fill in gaps for UI dev workflow

1. Switch to a new branch

2. If your workflow involves an IDE, generate your protos ./dev gen protobuf

• Your IDE relies on generated files for many tasks (e.g. code navigation, IntelliSense, debugging), and will complain unless you have re-generated those files.

  • If you need to re-generate all generated go files, use the slower ./dev gen go

  • If the above fails, run the slowest ./dev gen to update all of your generated files.

  • You may recall that with make , this step was not necessary. If you’re curious why, see this slack thread.

3. Write some code!

• If you add new files or imports, run ./dev gen bazel before compiling or running a test. compilepkg: missing strict dependencies: is usually the indicator that ./dev gen bazel needs to be re-run.

  • to skip this step, see tip below on ALWAYS_RUN_GAZELLE

• Build the binary: ./dev build short

4. Run a test

• On an IDE: your normal workflow should work if your generated files are up to date (See step 2).

• From the command line: ./dev test [path/to/pkg] --filter [test_name]

5. Before opening/updating a PR:

• Run ./dev lint --short (maybe additionally make lintshort as dev's linter doesn’t have 100% coverage yet)

• Assert your workspace is clean by running ./dev gen bazel . If you modified other generated files, run the appropriate ./dev gen [file_type] command.

General Bazel tips

• Bazel has a configuration file called .bazelrc. You can put a global configuration file at ~/.bazelrc or a per-repository file at .bazelrc.user in the root of your cockroach repo.

• Tired of running ./dev gen bazel? Set the ALWAYS_RUN_GAZELLE env-var to automatically run ./dev gen bazel before every dev test or dev build incantation. Note this does add a tiny delay – noticeable when iterating on small tests through dev test.

  • i.e. echo 'export ALWAYS_RUN_GAZELLE=1' >> ~/.zshrc

• bazel will fail with an error like ccache: error: Failed to create temporary file for /home/alyshanjahani/.ccache/tmp/message_li.stdout: Read-only file system. To avoid this you should get the ccache links out of your PATH manually (i.e. uninstall ccache).

  • Alternatively, if you would like to use Bazel with ccache, you can enable support for writing outside the sandbox by adding the following to your $HOME/.bazelrc or <repo>/.bazelrc.user file:
    - For MacOS/Darwin:

    build --sandbox_writable_path=/Users/<USER>/Library/Caches/ccache/

    - For Linux:

    build --sandbox_writable_path=/home/<USER>/.ccache

If you’re using a different ccache directory (ccache --get-config cache_dir) point to that instead.

I just want to use Bazel directly 😠

We recommend dev because it takes care of some common pitfalls for you and because it has a less wordy CLI (especially for tests), but you’re still welcome to directly use Bazel. A couple notes for those of you who wish to avoid dev:

• You should still ask dev doctor if your machine is up-to-snuff before you try to bazel build. The checks it performs aren’t dev-specific.

• dev prints out the (relevant) calls to bazel it makes before it does so. You can therefore run dev once just to learn how to ask Bazel to perform your build/test and then just directly call into bazel on subsequent iterations.

• If you want to build with the UI, you must include the --config with_ui argument to bazel build. (dev takes care of this for you if you are using it.)

• In general, test targets are named after the package under test plus the suffix _test. For example: bazel test pkg/sql/parser:parser_test. Note that there are exceptions: pkg/roachpb:string_test is one, and more may be added later.

• If you want to build a test without running it, you must include the the --config test argument to bazel build. (dev takes care of this for you if you are using it.)

• When running tests under stress, race, --rewrite, dev does the legwork to invoke with the necessary flags with bazel. This involves running under another binary (stress), running with certain gotags (race), or allowing certain paths outside the bazel sandbox to be written to (testdata). Feel free to see the actual bazel command invoked and tweak as necessary.