As always, we are grateful for the large PowerDNS community that is actively involved in improving the quality of our software, be it by submitting patches, by testing development versions of our software or helping debug interesting issues. We specifically want to thank Stefan Schmidt and Florian Weimer, who both over the years have helped tremendously in keeping PowerDNS fast, stable and secure.
This version of the PowerDNS Recursor contains a rather novel form of lock-free multithreading, a situation that comes close to the old '--fork' trick, but allows the Recursor to fully utilize multiple CPUs, while delivering unified statistics and operational control.
In effect, this delivers the best of both worlds: near linear scaling, with almost no administrative overhead.
Compared to 'regular multithreading', whereby threads cooperate more closely, more memory is used, since each thread maintains its own DNS cache. However, given the economics, and the relatively limited total amount of memory needed for high performance, this price is well worth it.
In practical numbers, over 40,000 queries/second sustained performance has now been measured by a third party, with a 100.0% packet response rate. This means that the needs of around 400,000 residential connections can now be met by a single commodity server.
In addition to the above, the PowerDNS Recursor is now providing resolver service for many more Internet users than ever before. This has brought with it 24/7 Service Level Agreements, and 24/7 operational monitoring by networking personnel at some of the largest telecommunications companies in the world.
In order to facilitate such operation, more statistics are now provided that allow the visual verification of proper PowerDNS Recursor operation. As an example of this there are now graphs that plot how many queries were dropped by the operating system because of a CPU overload, plus statistics that can be monitored to determine if the PowerDNS deployment is under a spoofing attack.
All in all, this is a large and important PowerDNS Release, paving the way for further innovation.
Note:
This release removes support for the 'fork' multi-processor option. In addition, the default is now to spawn two threads. This has been done in such a way that total memory usage will remain identical, so each thread will use half of the allocated maximum number of cache entries.
