Prometheus can use $valuevariables to output the value of the current alarm rule expression into the alarm information. But some floating-point values are quite long, which is very difficult to read, and it is even more unacceptable for patients with obsessive-compulsive disorder. How to make the alarm value "human readable"?
There are the following alarm rules to detect a certain domain name and send an alarm if the access time exceeds 0.5 seconds and lasts for more than 1 minute:
- name: blackbox-exporter
rules:
- alert: DomainAccessDelayExceeds0.5s
annotations:
description: 域名：{
{
$labels.instance }} 探测延迟大于 0.5 秒，当前延迟为：{
{
$value }}
summary: 域名探测，访问延迟超过 0.5 秒
expr: sum(probe_http_duration_seconds{
job=~"blackbox"}) by (instance) > 0.5
for: 1m
labels:
severity: warning
type: blackbox
When the traffic exceeds 0.5s, an alarm notification is triggered.
[1] Firing
Labels
alertname = DomainAccessDelayExceeds0.5s
instance = https://www.baidu.com
prometheus = monitoring/k8s
severity = warning
type = blackbox
Annotations
description = 域名：https://www.baidu.com 探测延迟大于 0.5 秒，当前延迟为：1.042937559
summary = 域名探测，访问延迟超过 0.5 秒
In the received alarm notification information, you can see that the delay time is up to 9 digits after the decimal point
There are three ways to format the value of the variable in the alarm rule $value:
{
{ printf "%.2f" $value }}
或
{
{ $value | printf "%.2f" }}
或
{
{ humanize $value }}
After testing {
{ printf "%.2f" $value }}or {
{ $value | printf "%.2f" }}adjustment, the alarm notification information received only has two decimal places; {
{ humanize $value }}it is three decimal places (for example: 1.262), or displayed as milliseconds (for example: 686.2m)