[Kimchi-devel] [PATCH][Wok] Add support to timestamps in clone naming function

[Aline Manera]

On 03/14/2016 02:54 PM, Rodrigo Trujillo wrote:
> There is a potential race condiction issue when some plugin tries to use
> the function get_next_clone_name(all_names, basename, name_suffix='').
> If clone requests are done so fast, it is possible that the plugin does
> not send all resource names in all_names parameter, then the function is
> going to select the same name for 2 or more clones, which is going to
> cause errors in the plugin.
>
> Supporting timestamps in microsecond precision, plugins can avoid this
> type of error coding its own race condiction fix or just using the
> timestamp function option.
> New name will be "basename-clone-timestamp-name-suffix".
>
> Signed-off-by: Rodrigo Trujillo <rodrigo.trujillo at linux.vnet.ibm.com>
> ---
>   src/wok/utils.py | 33 +++++++++++++++++++++------------
>   1 file changed, 21 insertions(+), 12 deletions(-)
>
> diff --git a/src/wok/utils.py b/src/wok/utils.py
> index 7e9a928..b80a80b 100644
> --- a/src/wok/utils.py
> +++ b/src/wok/utils.py
> @@ -31,6 +31,7 @@ import re
>   import sqlite3
>   import subprocess
>   import sys
> +import time
>   import traceback
>   import xml.etree.ElementTree as ET
>
> @@ -391,7 +392,7 @@ def remove_old_files(globexpr, hours):
>           wok_log.error(str(e))
>
>
> -def get_next_clone_name(all_names, basename, name_suffix=''):
> +def get_next_clone_name(all_names, basename, name_suffix='', ts=False):

Please, move this whole function to Kimchi. It is not related to any Wok 
feature so there is no reason to keep it here.

>       """Find the next available name for a cloned resource.
>
>       If any resource named "<basename>-clone-<number><name_suffix>" is found
> @@ -406,26 +407,34 @@ def get_next_clone_name(all_names, basename, name_suffix=''):
>           exist so that a resource named "foo.img" gets the name
>           "foo-clone-1.img" instead of "foo.img-clone-1". If this parameter
>           is used, the suffix should not be present in "basename".
> +    ts -- use timestamp, instead of incremental numbers
>
>       Return:
>       A UTF-8 string in the format "<basename>-clone-<number><name_suffix>".
>       """
>       re_group_num = 'num'
>
> -    re_expr = u'%s-clone-(?P<%s>\d+)' % (basename, re_group_num)
> -    if name_suffix != '':
> -        re_expr = u'%s%s' % (re_expr, name_suffix)
> +    # Use timestamps or increase clone number
> +    if ts:
> +        # Microsecond precision
> +        ts_suffix = int(time.time() * 1000000)
> +        new_name = u'%s-clone-%d' % (basename, ts_suffix)
> +    else:
> +        re_expr = u'%s-clone-(?P<%s>\d+)' % (basename, re_group_num)
> +        if name_suffix != '':
> +            re_expr = u'%s%s' % (re_expr, name_suffix)
>
> -    max_num = 0
> -    re_compiled = re.compile(re_expr)
> +        max_num = 0
> +        re_compiled = re.compile(re_expr)
>
> -    for n in all_names:
> -        match = re_compiled.match(n)
> -        if match is not None:
> -            max_num = max(max_num, int(match.group(re_group_num)))
> +        for n in all_names:
> +            match = re_compiled.match(n)
> +            if match is not None:
> +                max_num = max(max_num, int(match.group(re_group_num)))
> +
> +        # increments the maximum "clone number" found
> +        new_name = u'%s-clone-%d' % (basename, max_num + 1)
>
> -    # increments the maximum "clone number" found
> -    new_name = u'%s-clone-%d' % (basename, max_num + 1)
>       if name_suffix != '':
>           new_name = new_name + name_suffix
>