Hi,

We just released PowerDNS Recursor 4.1.11.

Since Spectre / Meltdown, system calls have become more expensive.  In 
addition, relevant versions of glibc turn out to implement `pthread_cond_wait` 
and `pthread_cond_signal` in such a way that they use multiple system calls 
always.
There is an optimization in glibc to improve this but it is disabled.

This new setup changes our protobuf logging so it amortizes system calls so we 
perform far less than one call per message.

Note that our previous `RemoteLogger` was configured in terms of how many 
messages it would buffer. Our new code is configured in terms of how many 
bytes. I have multiplied the configured numbers by 100 elsewhere (recursor 
config, dnsdist config) to sort of maintain parity.

In addition, the old `RemoteLogger` would buffer messages while there was no 
connection available. We no longer do this.

Finally new, every `reconnectTimeout` seconds we will flush our buffers 
opportunistically to not keep people waiting.

The changelog[1]:

- #7434: Add an option to export only responses over protobuf
- #7430: Reduce systemcall usage in protobuf logging

The tarball[2] (signature[3]) is available at 
https://downloads.powerdns.com/releases/  and packages for CentOS 6 and 7, 
Debian Jessie and Stretch, Ubuntu Bionic, Trusty and Xenial are available from 
https://repo.powerdns.com/  .

Please send us all feedback and issues you might have via the mailing list[4], 
or in case of a bug, via GitHub[5].

[1] https://doc.powerdns.com/recursor/changelog/4.1.html#change-4.1.11
[2] https://downloads.powerdns.com/releases/pdns-recursor-4.1.11.tar.bz2
[3] https://downloads.powerdns.com/releases/pdns-recursor-4.1.11.tar.bz2.sig
[4] https://mailman.powerdns.com/mailman/listinfo/pdns-users
[5] https://github.com/PowerDNS/pdns/issues/new
--
Erik Winkels
PowerDNS.COM BV -- https://www.powerdns.com

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