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  • Nikos Skalkotos's avatar
    Retry cleanup commands if they fail · f3845095
    Nikos Skalkotos authored
    Add a new try_fail_repeat function that wraps cleanup system commands
    and retries them if they fail. There are cases where commands like
    dmsetup, umount and losetup -d may fail with device is busy. In most
    of the cases, sleeping for halve a second and retrying does the job.
    f3845095
util.py 3.22 KiB
# Copyright 2012 GRNET S.A. All rights reserved.
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import sys
import sh
import hashlib
import time


class FatalError(Exception):
    pass


def get_command(command):
    def find_sbin_command(command, exception):
        search_paths = ['/usr/local/sbin', '/usr/sbin', '/sbin']
        for fullpath in map(lambda x: "%s/%s" % (x, command), search_paths):
            if os.path.exists(fullpath) and os.access(fullpath, os.X_OK):
                return sh.Command(fullpath)
        raise exception

    try:
        return sh.__getattr__(command)
    except sh.CommadNotFount as e:
        return find_sbin_command(command, e)


def try_fail_repeat(command, *args):

    times = (0.1, 0.5, 1, 2)
    i = iter(times)
    while True:
        try:
            command(*args)
            return
        except sh.ErrorReturnCode:
            try:
                wait = i.next()
            except StopIteration:
                break
            time.sleep(wait)

    raise FatalError("Command: `%s %s' failed" % (command, " ".join(args)))


class MD5:
    def __init__(self, output):
        self.out = output

    def compute(self, filename, size):
        MB = 2 ** 20
        BLOCKSIZE = 4 * MB  # 4MB

        prog_size = ((size + MB - 1) // MB)  # in MB
        progressbar = self.out.Progress(prog_size, "Calculating md5sum", 'mb')
        md5 = hashlib.md5()
        with open(filename, "r") as src:
            left = size
            while left > 0:
                length = min(left, BLOCKSIZE)
                data = src.read(length)
                md5.update(data)
                left -= length
                progressbar.goto((size - left) // MB)

        checksum = md5.hexdigest()
        progressbar.success(checksum)

        return checksum

# vim: set sta sts=4 shiftwidth=4 sw=4 et ai :