Re: Question regarding life time of backend threads in PDNS

Peter van Dijk <[email protected]> Thu, 7 Nov 2013 15:41:24 +0100

Newsgroups	gmane.network.dns.powerdns.devel
Message-ID	<[email protected]>

Hello Seema,

On Nov 7, 2013, at 6:19 , Seema Datar wrote:

> 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 - 
> 
> 	• What is the lifetime of a backend thread?

Sometimes, only one query.

> 	• How often does a thread get destroyed and a new  thread get created?

Some threads will live for a long time. Some other threads will come and go quickly.

> 	• Is there any interface available to do a cleanup before the thread ends?

Yes - the class destructor. Look at GeoBackend::~GeoBackend() or LUABackend::~LUABackend() for an example.

By the way, please keep these posts confined to the pdns-dev list.

Kind regards,
-- 
Peter van Dijk
Netherlabs Computer Consulting BV - http://www.netherlabs.nl/

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