We are launching a delay-sensitive system. We found one significant reason for the delay: some processes blocked DNS lookups for remote name servers. To mitigate this, we installed a local caching DNS filter, especially dnsmasq.
But we still see occasional significant pauses when requests to the local DNS cache ( dnsmasq) can take a long time. This is caused by TTL expiration; in these cases, it dnsmasqrequests its upstream server before responding to the local process.
We would also like to eliminate these pauses. I would like our local DNS cache to always respond immediately, even if the answer is out of date. The cache must request its upstream server asynchronously. For example, if the cache serves an outdated response, it may update this asynchronously. Or a more complicated policy is to update the cache asynchronously shortly before the TTL expires.
But I cannot find such a parameter for dnsmasqor for any other DNS caching servers that I was looking at. Are there any DNS servers designed to work in this configuration?
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