Date: Thu, 28 Sep 2017 12:28:55 +0200 From: Szabolcs Nagy <nsz@...t70.net> To: musl@...ts.openwall.com Cc: Srinivasa Raghavan <raghav135@...il.com> Subject: Re: DNS resolution happenning only after timeout * Srinivasa Raghavan <raghav135@...il.com> [2017-09-28 15:45:28 +0530]: > When using "Alpine" docker image which uses musl-libc, we are facing delay > when we do operations like below in our production environment, > 1. ping <name> > 2. nslookup <name> > 3. traceroute <name> > 4. http request from node.js > this bug may be related: https://github.com/rancher/rancher/issues/9961 > There is a 5 second delay in name resolution, and then the above command > returns the response. The same problem does not occur in "debian" docker > image (which uses GNU libc). > > In our case, there is a combination of SERVFAIL, "canonical name" along > with "Non authoritative answer". > > Some learnings after doing some trial and error: > 1. If I install "bind-tools" package in alpine, the "nslookup" happens > without delay. > 2. If I set "options timout:1" in /etc/resolv.conf , then the name is > resolved after 1 second (instead of 5 seconds). > 3. Whatever I change in /etc/resolv.conf (Like setting "domain", "search"), > there was no benefit. > 4. output of "host"/"nslookup" command shows "SERVFAIL" > 5. The problem does not occur if run from the host machine (Not from alpine > container). > 6. The problem does not occur if run from another container which uses Gnu > libc, like "Debian" image. > > Sample command outputs attached for reference. > > Request you to kindly help in debugging / resolution of this. > > Kind Regards, > R. Srinivasa Raghavan.
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