[chrony-users] Chrony behaviour on local reference mode

[Antoine Sgambato <asgambato@xxxxxxxxxxxxx>]

Dear all,

I have set up a chrony server with a local reference as the sole available source.
The server is correctly synchronized with the local clock:

Reference ID    : 7F7F0101 ()
Stratum         : 12
Ref time (UTC)  : Mon Oct 12 16:06:27 2020
System time     : 0.000000009 seconds slow of NTP time
Last offset     : -0.000005781 seconds
RMS offset      : 0.008687890 seconds
Frequency       : 63.148 ppm fast
Residual freq   : +0.000 ppm
Skew            : 0.000 ppm
Root delay      : 0.000000000 seconds
Root dispersion : 0.000000000 seconds
Update interval : 64.0 seconds
Leap status     : Normal

In particular the reference ID 7F7F0101 tells me that the local mode is operating (enabled with chronyc local stratum 12 orphan) and 

^? 127.127.1.0                  12  10   377   825    -11us[  -11us] +/-   17us

Then I add a server (chronyc add server 10.61.255.254 iburst maxpoll 6 port 123 prefer)
and I see chrony switching to this server. I now have:

Reference ID    : 0A3DFFFE (10.61.255.254)
Stratum         : 5
Ref time (UTC)  : Mon Oct 12 16:29:08 2020
System time     : 0.151633009 seconds fast of NTP time
Last offset     : +0.000192363 seconds
RMS offset      : 0.070889302 seconds
Frequency       : 63.148 ppm fast
Residual freq   : +184.986 ppm
Skew            : 0.132 ppm
Root delay      : 0.118800372 seconds
Root dispersion : 0.033694923 seconds
Update interval : 2.1 seconds
Leap status     : Normal

with the local clock still available:

^? 127.127.1.0                  12  10   377   180   -246ms[  -12us] +/- 2036us
^* 10.61.255.254                 4   6    37     7   -147us[  +11ms] +/-  103ms

So far it behave as I expected. But now if I remove the server I added (chronyc delete 10.61.255.254)
I would expect to return the the first situation. Instead after some time I end-up with this:

Reference ID    : 7F7F0100 (127.127.1.0)
Stratum         : 12
Ref time (UTC)  : Mon Oct 12 16:50:56 2020
System time     : 0.000032901 seconds fast of NTP time
Last offset     : +0.000018242 seconds
RMS offset      : 0.044247311 seconds
Frequency       : 72.399 ppm fast
Residual freq   : +0.025 ppm
Skew            : 9.118 ppm
Root delay      : 0.000058132 seconds
Root dispersion : 0.027406862 seconds
Update interval : 64.6 seconds
Leap status     : Normal

which is not exactly local mode (reference id is not 7F7F0101). Is this behavior correct? Local clock seems to be used:

^? 127.127.1.0                  12   6   377    20    -11us[  -11us] +/-   31ms


I also have an other question: from my experiments I noted that chrony "takes time" to switch the source used for synchronization to an other one when it becomes unreachable. The time I saw is greater than half an hour. Is there some configuration options that may be used to adjust this delay?

Kind regards,
Antoine.​