On Mon, May 18, 2009 at 8:29 PM, Tiberiu Motoc <[email protected]> wrote: > Hi, > > Very rarely (I estimate 1/250 times) I get the following error from > Curl: "Could not resolve host: [URL_host_name] (Domain name not > found)". I always access the same URL. I don't use a proxy, nor do I > use SSL. There is a company firewall setup, but I don't have access to > it. Today, there happened to be a problem with the firewall (I don't > know the details) and I've seen this error being generated more often. > I just don't know how to debug this. Does anyone have any idea why this > happens?
It could be your DNS server is sometimes slow to respond to a query or the query or reply gets eaten by the firewall or some other overloaded device between you and the DNS server. Try running a packet sniffer on your machine and watch for DNS queries and replies. When you get one of these errors, examine the packet sniffer logs to see if the reply from the DNS server went missing or took longer than usual. You could also try doing a bunch of DNS lookups using some other tool to see if it has the same problem, which would imply it is not libcurl's fault. e.g.: $ while :; do host your-server.example.com; sleep 1; done | tee /tmp/dnslookups.log But maybe without the "sleep 1", depending on how often your libcurl-based program normally tries to retrieve the URL. (Leaving out the sleep may or may not cause your DNS server admin to get upset.) -- Michael Wood <[email protected]>
