[chrony-users] Chrony forgets servers (specified by FQDN) when no DNS server

[Stephen Satchell <list@xxxxxxxxxxxx>]

TL;DR: chronyd doesn't like server specifications with FQDN when there 
is no DNS resolver available -- and neither does rival ntpd.  We'll see 
if NXDOMAIN is just as bad.

(I did check to see if this had already been reported -- didn't find any 
reference to issues like I experienced.  Went back two years.)

My story:

I live in a hilly area that experiences power dropouts of about 1.5 
seconds (more than a sag) during high winds.  Tonight, I had four such 
events.  My edge router rebooted each time.

My edge router (CentOS 7 on four-port box) is connected via ARRIS 
BGW210-700 broadband gateway to AT&T UVerse fiber (100/20).  As I am 
building this new edge router, I hadn't gotten A Round Tuit to set up 
caching DNS yet.  Translation: using 8.8.8.8 and 8.8.4.4 only.  I have a 
Time Machines GPS-based source indicated by IP address (10.1.1.15); the 
rest of the sources are downstream, called out with FQDNs.

After one of the power cycles, I checked matters with chronyc(1) and 
found the only active NTP server in the "sources" list was my local GPS 
NTP box.  Everything else was missing.  When I restarted chronyd, 
everything was there as expected.

Fortunately, I'm qualifying the circuit and new edge router, so nothing 
is live on it.

It would appear that not having DNS service available is fatal to 
bringing up a server.  So I have installed the caching DNS server so 
chrony will get *something* as a response; we'll see on the next power 
fail if things look better, or if NXDOMAIN results in the same.

By the way, I have another edge server running ntpd which *is* live, and 
it behaves the same way...so both NTP daemons have the same, er, difficulty.

Now some of you will be saying "where's your UPS"?  Another missing 
Round Tuit -- the box is in the garage waiting to be opened and tested 
before I tear my rack apart.

N.B.: the constant power cycling took out my LED desk lamp...

RFC: should I consider writing a script that will call chronyc to create 
the servers again, say once a day?
   1. Is this recommended?
   2. Would this tend to eventually add all the servers
      in [0123].centos.pool.ntp.org
   3. Is there a better way to "wake up" servers rejected
      because of no resolver, or NXDOMAIN if that causes drops?
   4. If not, may I make a feature request?

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