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bb detect nondeterminism

·Maggie Lou

You can now use the bb CLI to detect non-deterministic builds using the bb detect nondeterminism command.

The command runs a Bazel command twice with caching disabled, then compares the two compact execution logs with bb explain. Spans whose outputs differ between the two runs are reported as non-deterministic.

# By default, the command runs "build //...".
bb detect nondeterminism

# You can pass any Bazel command to run.
bb detect nondeterminism --bazel_command='build //foo:bar --config=linux'

Sending notifications​

To email all BuildBuddy org admins when non-determinism is detected, add --notify_email. To post a notification to a Slack channel, add --notify_slack=<SECRET_NAME>, where <SECRET_NAME> is the name of a BuildBuddy secret holding a Slack webhook URL.

Sending notifications requires an API key with the notification capability. Set it via the BB_NOTIFY_API_KEY environment variable:

BB_NOTIFY_API_KEY=<API_KEY> bb detect nondeterminism --notify_email

Running on a schedule​

To schedule a nightly nondeterminism check to catch regressions, you can configure a scheduled Workflow in your buildbuddy.yaml:

buildbuddy.yaml
actions:
  - name: Nondeterminism check
    triggers:
      schedule:
        crons:
          - "0 8 * * *" # 8:00 AM UTC every day
    steps:
      - run: bb detect nondeterminism --notify_email --notify_slack=SLACK_WEBHOOK_SECRET_NAME
    platform_properties:
      # Caching is disabled for this check anyway, so recycling adds little.
      recycle-runner: false
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