[Pdns-users] PowerDNS Recursor 3.2 Release Candidate 2 available

bert hubert bert.hubert at netherlabs.nl
Sun Feb 28 16:18:44 UTC 2010

Hash: SHA1

Hi everybody,

Please find below the release notes of the PowerDNS Recursor version 3.2,
Release Candidate 2. 

Compared to RC1, this version mostly contains compilation and platform
fixes (for Solaris and CentOS4/RHEL4), as well as improved statistics,
diagnostics and '--help' output. 

RC1 and RC2 are already deployed in a number of large places, and it appears
to be holding up well.  In addition, a number of future users have performed
stringent testing and performance measurements, and it appears this version
works satisfactorily. 

It is also observed that this release candidate provides for vastly improved
performance compared to 3.1.7.*, even bringing us close to the very
impressive numbers measured by users of the Nominum Vantio and Nominum CNS
software.  On modern hardware, the PowerDNS Recursor may in fact be faster,
and certainly better value for money. For more details, please see below.

If you are looking forward to deploying PowerDNS Recursor version 3.2, now
is a good time to testdrive RC2.

We are very interested in hearing your experiences, and look forward to
fixing any issues found before the final release is made. If nothing
important pops up, this is expected to happen next week. RC2 may be released
unchanged as the 3.2 "final".

Download from:

 * http://svn.powerdns.com/snapshots/rc2/
   (tar.bz2, "universal" i386/x86 .rpm and .deb packages, .pgp

   Please note that these 'universal' packages will not work on older
   distributions, including CentOS 4 and RHEL 4.

(Nominum, Nominum CNS & Nominum Vantio are trademarks owned by

Release notes
- -------------
Version with clickable links:


          Lua scripts from version 3.1.7.* are fully compatible with
          version 3.2. However, scripts written for development snapshot
          releases, are NOT. Please see Section 12.6 for details!

The 3.2 release is the first major release of the PowerDNS Recursor in a
long time.  Partly this is because 3.1.7.* functioned very well, and
delivered satisfying performance, partly this is because in order to really
move forward, some heavy lifting had to be done.

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

All in all, this is a large and important PowerDNS Release, paving the way
for further innovation.


     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.

Changes between RC1 and RC2:

  * Compilation on Solaris 10 has been fixed (various
    patchlevels had different issues), code in commit 1522.
  * Compatibility with CentOS4/RHEL4 has been restored, the gcc
    and glibc versions shipped with this distribution contain a
    Thread Local Storage bug which we now work around. Thanks
    to Darren Gamble and Imre Gergely for debugging this issue,
    code in commit 1527.
  * A failed setuid operation, because of misconfiguration,
    would result in a crash instead of an error message. Fixed
    in commit 1523.
  * Imre Gergely discovered that PowerDNS was doing spurious
    root repriming when invalidating nssets. Fixed in commit
  * Imre Gergely discovered our rrd graphs had not been changed
    for the new multithreaded world, and did not allow scaling
    beyond 200% cpu use. In addition, CPU usage graphs did not
    add up correctly. Implemented in commit 1524.
  * Andreas Jakum discovered the description of
    'max-packetcache-entries' and 'forward-zones-recurse' was
    wrong in the output of '--help' and '--config'. In
    addition, some stray backup files made it into the RC1
    release. Addressed in commit 1529.


  * Multithreading, allowing near linear scaling to multiple
    CPUs or cores. Configured using 'threads=' (many commits).
    This also deprecates the '--fork' option.
  * Added ability to read a configuration item of a running
    PowerDNS Recursor using 'rec_control get-parameter' (commit
    1243), suggested by Wouter de Jong.
  * Added ability to read all statistics in one go of a running
    PowerDNS Recursor using 'rec_control get-all' (commit
    1496), suggested by Michael Renner.
  * Speedups in packet generation (Commits 1258, 1259, 1262)
  * TCP deferred accept() filter is turned on again for slight
    DoS protection. Code in commit 1414.
  * PowerDNS Recursor can now do TCP/IP queries to remote IPv6
    addresses (commit 1412).
  * Solaris 9 '/dev/poll' support added, Solaris 8 now
    deprecated. Changes in commit 1421, commit 1422, commit
    1424, commit 1413.
  * Lua functions can now also see the address _to_ which a
    question was sent, using getlocaladdress(). Implemented in
    commit 1309 and commit 1315.
  * Maximum cache sizes now default to a sensible value.
    Suggested by Roel van der Made, implemented in commit 1354.
  * Domains can now be forwarded to IPv6 addresses too, using
    either ::1 syntax or [::1]:25. Thanks to Wijnand Modderman
    for discovering this issue, fixed in commit 1349.
  * Lua scripts can now load libraries at runtime, for example
    to calculate md5 hashes. Code by Winfried Angele in commit
  * Periodic statistics output now includes average queries per
    second, as well as packet cache numbers (commit 1493).
  * New metrics are available for graphing, plus added to the
    default graphs (commit 1495, commit 1498, commit 1503)
  * Fix errors/crashes on more recent versions of Solaris 10,
    where the ports functions could return ENOENT under some
    circumstances. Reported and debugged by Jan Gyselinck,
    fixed in commit 1372.

New features:

  * Add pdnslog() function for Lua scripts, so errors or other
    messages can be logged properly.
  * rec_control now accepts a --timeout parameter, which can be
    useful when reloading huge Lua scripts. Implemented in
    commit 1366.
  * Domains can now be forwarded with the 'recursion-desired'
    bit on or off, using either forward-zones-recurse or by
    prefixing the name of a zone with a '+' in
    forward-zones-file. Feature suggested by Darren Gamble,
    implemented in commit 1451.
  * Access control lists can now be reloaded at runtime
    (implemented in commit 1457).
  * PowerDNS Recursor can now use a pool of
    query-local-addresses to further increase resilience
    against spoofing. Suggested by Ad Spelt, implemented in
    commit 1426.
  * PowerDNS Recursor now also has a packet cache, greatly
    speeding up operations. Implemented in commit 1426, commit
    1433 and further.
  * Cache can be limited in how long it maximally stores
    records, for BIND compatibility (TTL limiting), by setting
    max-cache-ttl.Idea by Winfried Angele, implemented in
    commit 1438.
  * Cache cleaning turned out to be scanning more of the cache
    than necessary for cache maintenance. In addition, far more
    frequent but smaller cache cleanups improve responsiveness.
    Thanks to Winfried Angele for discovering this issue.
    (commits 1501, 1507)
  * Performance graphs enhanced with separate CPU load and
    cache effectiveness plots, plus display of various overload
    situations (commits 1503)

Compiler/Operating system/Library updates:

  * PowerDNS Recursor can now compile against newer versions of
    Boost (verified up to and including 1.42.0). Reported &
    fixed by Darix in commit 1274. Further fixes in commit
    1275, commit 1276, commit 1277, commit 1283.
  * Fix compatibility with newer versions of GCC (closes ticket
    ticket 227, spotted by Ruben Kerkhof, code in commit 1345,
    more fixes in commit 1394, 1416, 1440).
  * Rrdtool update graph is now compatible with FreeBSD out of
    the box. Thanks to Bryan Seitz (commit 1517).
  * Fix up Makefile for older versions of Make (commit 1229).
  * Solaris compilation improvements (out of the box, no
    handwork needed).
  * Solaris 9 MTasker compilation fixes, as suggested by John
    Levon. Changes in commit 1431.

Bug fixes:

  * Under rare circumstances, the recursor could crash on 64
    bit Linux systems running glibc 2.7, as found in Debian
    Lenny. These circumstances became a lot less rare for the
    3.2 release. Discovered by Andreas Jakum and debugged by
    #powerdns, fix in commit 1519.
  * Configuration parser is now resistant against trailing tabs
    and other whitespace (commit 1242)
  * Fix typo in a Lua error message. Close ticket 210, as
    reported by Stefan Schmidt (commit 1319).
  * Profiled-build instructions were broken, discovered & fixes
    suggested by Stefan Schmidt. ticket 239, fix in commit
  * Fix up duplicate SOA from a remote authoritative server
    from showing up in our output (commit 1475).
  * All security fixes from are included.
  * Under highly exceptional circumstances on FreeBSD the
    PowerDNS Recursor could crash because of a TCP/IP error.
    Reported and fixed by Andrei Poelov in ticket 192, fixed in
    commit 1280.
  * PowerDNS Recursor can be a root-server again. Error spotted
    by the ever vigilant Darren Gamble (t229), fix in commit
  * Rare TCP/IP errors no longer lead to PowerDNS Recursor
    logging errors or becoming confused. Debugged by Josh Berry
    of Plusnet PLC. Code in commit 1457.
  * Do not hammer parent servers in case child zones are
    misconfigured, requery at most once every 10 seconds.
    Reported & investigated by Stefan Schmidt and Andreas
    Jakum, fixed in commit 1265.
  * Properly process answers from remote authoritative servers
    that send error answers without including the original
    question (commit 1329, commit 1327).
  * No longer spontaneously turn on 'export-etc-hosts' after
    reloading zones. Discovered by Paul Cairney, reported in
    ticket 225, addressed in commit 1348.
  * Very abrupt server failure of large numbers of high-volume
    authoritative servers could trigger an out of memory
    situation. Addressed in commit 1505.
  * Make timeouts for queries to remote authoritative servers
    configurable with millisecond granularity. In addition, the
    old code turned out to consider the timeout expired when
    the integral number of seconds since 1970 increased by 1 -
    which *on average* is after 500ms. This might have caused
    spurious timeouts! New default timeout is 1500ms. See
    network-timeout setting for more details. Code in commit

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