Re: Question regarding life time of backend threads in PDNS

Hi All,

I had a followup question. I am assuming there can be only one backend
instance per thread. Can you please confirm that? So, basically if there
are 8 threads of execution, can I assume that there are only 8 backend
instances running?

Thanks,
Seema

On 11/8/13 1:03 PM, "Aki Tuomi" <[email protected]> wrote:

>On Fri, Nov 08, 2013 at 07:22:40AM +0000, Seema Datar wrote:
>> Hi All,
>> 
>> Does anybody have more information on this?
>> 
>> Thanks,
>> Seema
>> 
>> Hi All,
>> 
>> We have a use case where we use PDNS with 8 backend threads. We needed
>>to save thread specific data in an mmap. However, I came across the
>>following in PDNS documentation -
>> 
>> PowerDNS may instantiate multiple instances of your backend, or destroy
>>existing copies and instantiate new ones. Backend code should therefore
>>be thread-safe with respect to its static data. Additionally, it is wise
>>if instantiation is a fast operation, with the possible exception of the
>>first construction.
>> 
>> The questions I had are -
>> 
>> 
>>   1.  What is the lifetime of a backend thread?
>>   2.  How often does a thread get destroyed and a new  thread get
>>created?
>>   3.  Is there any interface available to do a cleanup before the
>>thread ends?
>> 
>> Thanks,
>> Seema
>
>Lifetime of a backend thread is dependant on several factors, and the only
>thing you can assume is that it's not something you can rely on.
>
>The only thing backend module can use for cleanup is the destructror of
>the 
>backend class. 
>
>Or if you use remote/pipebackend, you can wire it to look for EOF or
>signal 
>and cleanup when either one is received before dying out.
>
>Aki Tuomi