graphite retention schema breakdown

graphite_retention_schema_breakdown.py

def archive_to_bytes(archive):
    def to_seconds(s):
        SECONDS_IN_A = {
            's': 1,
            'm': 1 * 60,
            'h': 1 * 60 * 60,
            'd': 1 * 60 * 60 * 24,
            'y': 1 * 60 * 60 * 24 * 365,
        }

        return int(s[:-1]) * SECONDS_IN_A[s[-1]]
    old_archive = archive
    archive = [map(to_seconds, point.split(':'))
               for point in archive.split(',')]

    SIZE_METADATA = 2 * 4 + 4 + 4  # 16 [!2LfL]
    SIZE_ARCHIVE_INFO = 3 * 4  # 12 [!3L]+
    SIZE_POINT = 4 + 8  # 12 [!Ld]+

    size = 0
    for (n_points, (resolution, retention)) in zip(old_archive.split(','), archive):
	level_size = SIZE_ARCHIVE_INFO + SIZE_POINT * retention/resolution
        size += level_size
	print('{:<10}: {:>4} points --> {:>6} KiB'.format(n_points, int(retention/resolution), level_size/1000))

    if size:
        size += SIZE_METADATA

    return size