I can see such a warning in the dynatrace server log from time to time，WARNING[CachingFqdnResolver]Failed ro resolve DNS for IP "xx.xx.xx.xx"-had following exception:com.dynatrace.diagnostics.sdk.net.FqdnResolutionException:Cannot resolve FQDN for IP xx.xx.xx.xx.
The following message appears before that，agent unregistered from collector .Sometimes the fault can return to normal in 0 seconds, sometimes for several minutes.What does this mean and where is the problem? I am looking forward your reply.Thank you.
It looks like the Dynatrace Server is having issues performing reverse DNS lookups. It's trying to figure out what domain is associated with that IP address but cannot resolve it.
Try logging into the server machine and performing an "nslookup" on the IP addresses that appear in the log warnings.
Also... do you recognise the IP address? Is it a collector? or an agent?
This shouldnt be a problem. OUr agents simply try to resolve the full qualified domain name of the agent. this name will eventually show up in dynatrace in case we get the name. if we cant query it we simply just show the host name or the IP Address