node_time_zone_offset_seconds doesn't reflect timezone change

[datuxing]

Host operating system: output of uname -a

Linux 3.10.0-1160.36.2.el7.x86_64

node_exporter version: output of node_exporter --version

version 1.3.1

node_exporter command line flags

N/A

Are you running node_exporter in Docker?

No

What did you do that produced an error?

changed system timezone, but node_time_zone_offset_seconds still showing previous timezone.
after restart node_exporter service, it can collect correct timezone info.

What did you expect to see?

expect to get timezone change using node_time_zone_offset_seconds as soon as possible.

What did you see instead?

node_time_zone_offset_seconds still showing previous timezone.

[discordianfish]

Hrmm this is unexpected.. we read the zoneinfo data on every scrape:

• https://github.com/prometheus/node_exporter/blob/master/collector/zoneinfo_linux.go#L54
• https://github.com/prometheus/procfs/blob/master/zoneinfo.go#L75

[datuxing]

Hrmm this is unexpected.. we read the zoneinfo data on every scrape:

• https://github.com/prometheus/node_exporter/blob/master/collector/zoneinfo_linux.go#L54
• https://github.com/prometheus/procfs/blob/master/zoneinfo.go#L75

I saw node_time_zone_offset_seconds is collect by https://github.com/prometheus/node_exporter/blob/master/collector/time.go#L71

I have run a simple golang code continue to print time.Now().Zone() in a loop, and it always print pervious timezone after changed system timezone. maybe golang runtime can't detect timezone change?

[datuxing]

Hrmm this is unexpected.. we read the zoneinfo data on every scrape:

• https://github.com/prometheus/node_exporter/blob/master/collector/zoneinfo_linux.go#L54
• https://github.com/prometheus/procfs/blob/master/zoneinfo.go#L75

I saw node_time_zone_offset_seconds is collect by https://github.com/prometheus/node_exporter/blob/master/collector/time.go#L71

I have run a simple golang code continue to print time.Now().Zone() in a loop, and it always print pervious timezone after changed system timezone. maybe golang runtime can't detect timezone change?

seems it's known issue of golang, golang/go#28020
so node_time_zone_offset_seconds can't reflect timezone change if it collect by using golang time.Now().Zone()

[SuperQ]

We might want to add a note to the README to mention that changes require a restart of the exporter.