tiup cluster check also support Chrony as NTP implementation

[yahonda]

Feature Request

"tiup cluster check" command to support Chrony as NTP implementation in addition to ntpd

Why the featue is needed:
Starting from Red Hat Enterprise 7 and Ubuntu 18.04, both Linux distributions added support Chrony as NTP as well as ntpd.

In some cases Chronyd is better than ntpd as described in these documentations.

https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/ch-configuring_ntp_using_the_chrony_suite

chronyd can usually synchronize the clock faster and with better accuracy.

https://ubuntu.com/blog/ubuntu-bionic-using-chrony-to-configure-ntp

Starting with Ubuntu Bionic, the choice for fast and accurate time synchronization is chrony.

Describe alternatives you've considered:
Use current ntpd.

Teachability, Documentation, Adoption, Migration Strategy:
It looks like checkNTP depends on ntpd implementation, does not look like supporting chrony.

tiup/pkg/cluster/operation/check.go

Lines 194 to 210 in c925128

	func checkNTP(ntpInfo *insight.TimeStat) *CheckResult {
	result := &CheckResult{
	Name: CheckNameNTP,
	}
	if ntpInfo.Status == "none" {
	zap.L().Info("The NTPd daemon may be not installed, skip.")
	return result
	}
	// check if time offset greater than +- 500ms
	if math.Abs(ntpInfo.Offset) >= 500 {
	result.Err = fmt.Errorf("time offet %fms too high", ntpInfo.Offset)
	}
	return result
	}

[yahonda]

cc @makocchi-git

[dveeden]

Some history on this: pingcap/docs#5283

Isn't RHEL using Chrony starting with RHEL8 and not RHEL7?

[yahonda]

I have created a new EC2 instance using "Red Hat Enterprise Linux 7 with High Availability" at AWS Marketplace AMI. It installs and starts up chrony by default.

[ec2-user@ip-172-31-43-69 ~]$ more /etc/redhat-release
Red Hat Enterprise Linux Server release 7.9 (Maipo)

[ec2-user@ip-172-31-43-69 ~]$ rpm -qa |grep ntp
fontpackages-filesystem-1.44-8.el7.noarch
[ec2-user@ip-172-31-43-69 ~]$ rpm -qa |grep chro
chrony-3.4-1.el7.x86_64
[ec2-user@ip-172-31-43-69 ~]$ sudo systemctl status chrony
Unit chrony.service could not be found.
[ec2-user@ip-172-31-43-69 ~]$ sudo systemctl status chronyd
● chronyd.service - NTP client/server
   Loaded: loaded (/usr/lib/systemd/system/chronyd.service; enabled; vendor preset: enabled)
   Active: active (running) since Wed 2022-01-05 01:21:38 UTC; 2min 19s ago
     Docs: man:chronyd(8)
           man:chrony.conf(5)
 Main PID: 624 (chronyd)
   CGroup: /system.slice/chronyd.service
           └─624 /usr/sbin/chronyd

Jan 05 01:21:37 localhost.localdomain systemd[1]: Starting NTP client/server...
Jan 05 01:21:38 localhost.localdomain chronyd[624]: chronyd version 3.4 starting (+CMDMON +NTP +REFCLOCK +RTC +PRIVD...EBUG)
Jan 05 01:21:38 localhost.localdomain systemd[1]: Started NTP client/server.
Jan 05 01:21:45 ip-172-31-43-69.us-east-2.compute.internal chronyd[624]: Selected source 169.254.169.123
Hint: Some lines were ellipsized, use -l to show in full.
[ec2-user@ip-172-31-43-69 ~]$

[makocchi-git]

tiup uses tidb-insight inside. So we need to implement tidb-insight for checking chrony just like ntp.
Fortunately, it's already done by the latest commit 👍

[dveeden]

@yahonda from https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/7/html/system_administrators_guide/ch-configuring_ntp_using_the_chrony_suite :

"The chrony suite is installed by default on some versions of Red Hat Enterprise Linux 7"

This means our tools and documentation should include details about and support for Chrony. https://docs.pingcap.com/tidb/stable/check-before-deployment#check-and-install-the-ntp-service already included details about Chrony, no follow up needed for the docs.

[AstroProfundis]

Indeed, we have added support for tidb-insight recently, and we'll do some tests and adjust how tiup-cluster handles the output of tidb-insight collector in the check subcommand before we can make that a new release.

[yahonda]

Thanks for the update. I'm looking for the future version of tiup supporting Chrony implementation.