On Wed, 10 May 2023 09:56:08 +0200 Ingeborg Hellemo ingeborg.hellemo@uit.no wrote:
Does this happen real time or is there som internal caching involved?
It's real-time *with* caching. I.e. there's a response cache per web UI process. If there is no cache hit, the DNS queries are sent out and the corresponding responses cached.
But, the cache is an LRU cache with 128 slots (the default value of the cache implementation), which might not be a good idea for this purpose. This means that once the cache contains 128 host lookups, the least recently used cache entry is evicted. If you only ever use the host information button for the same handful of devices, the DNS responses will basically be cached indefinitely, or until the process is restarted, whichever comes first.
Process restarts are also entirely deployment-specific. We typically deploy with a configuration that kills and restarts the worker processes after a certain number of requests have been handled by it.
Is there some case sensitivity involved? After making sure that both A and PTR RR had the same case plus a reload of apache, I am getting the expected output.
Well, the cache key is the hostname/sysname as known by NAV, which ultimately comes from the PTR record for the device's IP address. If you change the casing of the PTR record in DNS, you also effectively invalidate the ipdevinfo DNS cache for that host.