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

[Rodrigo Trujillo]

Ok, please ignore this patch.

Rodrigo

On 03/14/2016 04:02 PM, Aline Manera wrote:
>
>
> 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
>>
>
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