The chrony module

Provides time synchronization on all cluster nodes using the chrony utility.

How it works

The module starts chrony agents on all cluster nodes.

By default, the NTP server pool.ntp.org is used. The NTP server can be changed via the settings module. To view the NTP servers used, you can use the command:

kubectl exec -it -n d8-chrony chrony-master-r7v6c -- chronyc -N sources
Defaulted container "chrony" out of: chrony, chrony-exporter, kube-rbac-proxy
MS Name/IP address         Stratum Poll Reach LastRx Last sample
===============================================================================
^* pool.ntp.org.                 2  10   377   171   -502us[ -909us] +/- 5388us
^- pool.ntp.org.                 2  10   377   666  -5317us[-5698us] +/-  103ms
^+ pool.ntp.org.                 2  10   377   938   -201us[ -567us] +/- 5346us
^+ pool.ntp.org.                 2  10   377   843   -159us[ -530us] +/-   12ms

^+ - combined NTP server (chrony combines information from combined servers to reduce inaccuracies);
^* - current NTP server;
^- - non-combinable NTP server.

chrony agents on master nodes and on other nodes have one main difference - on all nodes that are not masters, the list of NTP servers contains not only NTP servers from module config, but also the addresses of all master nodes of the cluster.

Thus, agents on master nodes synchronize time only from the list of hosts specified in module config (by default from pool.ntp.org). And agents on other nodes synchronize time with the list of NTP servers from module config plus with chrony agents on master nodes.

This is done so that in case of unavailability of NTP servers specified in module config, the time is synchronized with the master nodes.