Hi all,

I have started replacing my dnsdist servers that are running Debian Stretch with the updated Debian Buster release. I came across an issue where dnsdist is running for a period of time it will stop answering any UDP queries until it is restarted. Sending queries either externally to the server or from the server itself results in a timeout.

The server is running on bare metal and is receiving around 900-1200 queries/second. There is multiple dnsdist instances running for different purposes, there is 8 instances total. Each instance is bound to a different set of IP's, no IP's are shared between dnsdist instances. For better performance I am using reusePort with 4 listeners normally, for this issue I tried removing the additional listeners and removing the reusePort setting but it still occured.

With reusePort enabled the issue occurs after a short period of time usually between 30 and 40 seconds from the period queries start getting sent to it. Without reusePort enabled and a single listen thread the issue seems to occur after around 4-5 hours, when it occurs the symptom seems the same. Once the issue occurs it doesn't seem to recover itself (I waited for around 30 hours) until the dnsdist service is restarted.

The dnsdist console and API/web interface continues to work. I can also see dnsdist sending out the health checking queries to the backends and it correctly marks them as up or down. TCP queries also work fine.

I had a look through the servers logs but couldn't find anything that could be related to this problem in syslog/messages/dmesg. I do raise the open file limit and the tasksmax limits applied by systemd.

The configuration I am using has been migrated from the older 1.3 dnsdist release with a few changes to the configuration to make use of newer features as the config was built a few years ago.

I also gave the current master release a go but that also had the same problem.

I am wondering if anyone else has had the same issue? If the configuration I am using would be useful I can upload a copy of that.

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