Compared to the previous major (4.5) release of PowerDNS Recursor, this release contains several sets of changes:

• The ability to flush records from the caches on a incoming notify requests. Many thanks to Kevin P. Fleming for this feature!
• A rewrite of the outgoing TCP code, adding both re-use of connections and support for DoT to authoritative servers or forwarders.
• Many improvements in the area of metrics: more metrics are collected and more metrics are now exported in a Prometheus friendly way.
• A new Zone to Cache function that will retrieve a zone (using AXFR, HTTP, HTTPS or a local file) periodically and insert the contents into the record cache, allowing the cache to be always hot for a zone. This can be used for the root or any other zone.
• An experimental Event Tracing function, providing insight into the time taken by the steps in the process of resolving a name.

Re-use of TCP/DoT connections is achieved by not closing connections, leaving them open for re-use. Previously, a TCP connection would be closed after a single query-reply exchange. The policy used to keep idle connections open is governed by various settings.

By default, if a forwarder is specified using port 853, DoT will be used to connect to that forwarder. It is also possible to list specific nameservers that should be contacted over DoT. Note that no certificate validation is done. After the standard committees define discovery of authoritative servers offering DoT, we will add functionality to allow automatic switching to DoT including validation of certificates.

As always, there are also many smaller bug fixes and improvements, please refer to the changelog for additional details. When upgrading do not forget to check the upgrade guide.

Please send us all feedback and issues you might have via the mailing list, or in case of a bug, via GitHub.

The tarball (signature) is available from our download server and packages for several distributions are available from our repository.

With this 4.6.0 release, the 4.3.x releases will be marked EOL and the 4.4.x and 4.5.x releases will go into critical fixes only mode. Consult the EOL policy for more details.

We would also like to mention that with the 4.5 release we stopped supporting systems using 32-bit time. This includes most 32-bit Linux platforms.

We are grateful to the PowerDNS community for the reporting of bugs, issues, feature requests, and especially to the submitters of fixes and implementations of features.