[SR-Users] cfgutils lock / unlock + $sht() variables.

[Daniel-Constantin Mierla]

Hello,

On 6/29/12 11:07 PM, Vitaliy Aleksandrov wrote:
> Hi all,
>
> I use $sht() pseudo-variabled provided by htable module for caching 
> various information about sip customers. I thought that htable has 
> some locking mechanism inside it and today while i was reading 
> core-cookbook i payed attention to one example with the lock/unlock 
> functions and $sht():
>
> lock("calls-to::10.10.10.10");
> $sht(a=>calls-to::10.10.10.10) =
>             $sht(a=>calls-to::10.10.10.10) + 1;
> unlock("calls-to::10.10.10.10");
>
> According to that example an explicit locking mechanism should be used 
> when i want to write something to a hash table.
> On the other hand there are no locks in htable documentation.
>
> So the question is when do the explicit locks should be used and for 
> what purpose ?
reading and writing in hash table is under the lock. But the increment 
operation as it is presented above requires first to read and then to 
write -- for that is recommended you use a lock to avoid races.

If it is just increment/decrement operation in htable, then you can use 
$shtinc(...)/$shtdec(...) for it:

http://www.kamailio.org/wiki/cookbooks/3.3.x/pseudovariables#shtinc_htable_key

Cheers,
Daniel

-- 
Daniel-Constantin Mierla - http://www.asipto.com
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