Hmbown/CodeWhale · error · PersistenceBacklogError

measurement command failed

Error message

measurement command failed

What it means

measure() in scripts/check-persistence-backlog-budget.py runs scripts/measure-persistence-backlog.py as a subprocess with CARGO_NET_OFFLINE=true; this error means that child exited non-zero. The child's stderr is forwarded and its stdout printed before the raise, so the real failure (usually a cargo build/test problem or a dirty source tree) appears directly above this message. The wrapper deliberately converts any child failure into this single contract error.

Source

Thrown at scripts/check-persistence-backlog-budget.py:386

            decreases.append((field, current, ceiling))
    return increases, decreases


def measure() -> dict[str, Any]:
    env = os.environ.copy()
    env["CARGO_NET_OFFLINE"] = "true"
    result = subprocess.run(
        [sys.executable, str(MEASURE_SCRIPT)],
        cwd=ROOT,
        env=env,
        text=True,
        capture_output=True,
        check=False,
    )
    sys.stderr.write(result.stderr)
    if result.returncode != 0:
        sys.stdout.write(result.stdout)
        raise PersistenceBacklogError("measurement command failed")
    try:
        receipt = json.loads(result.stdout)
    except json.JSONDecodeError as error:
        raise PersistenceBacklogError(f"measurement emitted invalid JSON: {error}") from error
    if not isinstance(receipt, dict):
        raise PersistenceBacklogError("measurement receipt must be an object")
    return receipt


def main() -> int:
    parser = argparse.ArgumentParser(description=__doc__)
    parser.add_argument("--receipt", type=Path, help="check an existing receipt")
    parser.add_argument("--budget", type=Path, default=BUDGET_PATH)
    args = parser.parse_args()
    try:
        expected_source = current_source_identity()
        receipt = load_json(args.receipt, "receipt") if args.receipt else measure()
        budget = load_json(args.budget, "budget")

View on GitHub (pinned to 8880682c63)

Solutions

1. Read the forwarded child output immediately above the error line — it contains the actual failure
2. Reproduce directly: `python3 scripts/measure-persistence-backlog.py`
3. Pre-populate the cargo cache with `cargo fetch` so the forced-offline build succeeds
4. Commit or stash local changes; the measurement requires a clean source tree
5. Fix any compile error the child reported, then re-run the checker

Example fix

# before
python3 scripts/check-persistence-backlog-budget.py   # ERROR: measurement command failed
# after
cargo fetch
git stash --include-untracked
python3 scripts/measure-persistence-backlog.py && python3 scripts/check-persistence-backlog-budget.py

import shutil
assert shutil.which('cargo') and shutil.which('rustc'), 'toolchain missing'
subprocess.run(['cargo', 'fetch'], cwd=ROOT, check=True)  # warm the offline cache

try:
    receipt = measure()
except PersistenceBacklogError:
    # child stderr/stdout were already forwarded above; fix the root cause there
    raise

When it happens

Trigger: Invoking the checker without --receipt on a machine where the forced-offline cargo build fails because required crates are not in the local cache; a workspace compile error; the measure script's own validation failing (for example on a dirty git tree); rustc or cargo missing from PATH.

Common situations: First run on a fresh machine or CI container without `cargo fetch`; local uncommitted changes making the tree dirty; a broken commit in the workspace; toolchain not installed.

Related errors

• runtime-contract measurement failed with exit code {proc.ret
• measurement emitted invalid JSON: {error}
• exact library metric test {metric_test_name(test_name)} ran
• missing {marker.rstrip()} marker from exact library metric t
• failed to read git range {commit_range!r}: {exc}

AI-assisted analysis of Hmbown/CodeWhale@8880682c63 (2026-08-16). Data as JSON: /api/errors/99f4d0a1b5fef109. Report an issue: GitHub.