def batch_checkout()

in libmozevent/utils.py [0:0]

• 28 lines of code
• 5 McCabe index (conditional complexity)

def batch_checkout(repo_url, repo_dir, revision=b"tip", batch_size=100000):
    """
    Helper to clone a mercurial repository using several steps
    to minimize memory footprint and stay below 1Gb of RAM
    It's used on Heroku small dynos, and support restarts
    """
    assert isinstance(revision, bytes)
    assert isinstance(batch_size, int)
    assert batch_size > 1

    log.info("Batch checkout", url=repo_url, dir=repo_dir, size=batch_size)
    try:
        cmd = hglib.util.cmdbuilder(
            "clone", repo_url, repo_dir, noupdate=True, verbose=True, stream=True
        )
        hg_run(cmd)
        log.info("Initial clone finished")
    except hglib.error.CommandError as e:
        if e.err.startswith(
            "abort: destination '{}' is not empty".format(repo_dir).encode("utf-8")
        ):
            log.info("Repository already present, skipping clone")
        else:
            raise

    repo = hglib.open(repo_dir)
    start = max(int(repo.identify(num=True).strip().decode("utf-8")), 1)
    target = int(repo.identify(rev=revision, num=True).strip().decode("utf-8"))
    if start >= target:
        return
    log.info("Will process checkout in range", start=start, target=target)

    steps = list(range(start, target, batch_size)) + [target]
    for rev in steps:
        log.info("Moving repo to revision", dir=repo_dir, rev=rev)
        repo.update(rev=rev)