feat(monitoring): add VM packets drop alert

[Yaguang Tang (yaguangtang)]

No description provided.

[Copilot]

Pull request overview

This PR introduces Prometheus alerting for libvirt virtual machine interface packet drops, wiring the new alert rules into the kube-prometheus-stack jsonnet mixin system and documenting the new alerts.

Changes:

• Add two new alerts for VM interface receive/transmit packet drops (P3) under a new libvirt alert group.
• Add promtool rule tests covering negative/positive cases for both alerts.
• Add operator documentation + a release note describing the new alerts.

Reviewed changes

Copilot reviewed 5 out of 5 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
roles/kube_prometheus_stack/files/jsonnet/tests.yml	Adds promtool test cases for the new libvirt drop alerts.
roles/kube_prometheus_stack/files/jsonnet/mixins.libsonnet	Registers the new libvirt jsonnet mixin so its alert group is rendered.
roles/kube_prometheus_stack/files/jsonnet/libvirt.libsonnet	Defines LibvirtDomainInterfaceReceiveDrops and LibvirtDomainInterfaceTransmitDrops alerts.
releasenotes/notes/add-libvirt-interface-drop-alerts-5a7e1d9552a1a38e.yaml	Adds a feature release note for the new alerts.
doc/source/admin/monitoring.rst	Adds runbook-style documentation entries for both new alerts.

[Copilot]

Pull request overview

Copilot reviewed 5 out of 5 changed files in this pull request and generated 1 comment.

[Copilot]

For consistency with the other custom alert files, consider defining helper locals at file scope and keeping rules as a plain array literal. For example, coredns.libsonnet and nginx.libsonnet define locals at the top of the file and use rules: [ ... ], which is easier to scan and keeps alert rule objects more uniform.

Suggested change

	{
	prometheusAlerts+: {
	groups+: [
	{
	name: 'libvirt',
	rules:
	local dropAlert(direction) =
	local capitalized = std.asciiUpper(std.substr(direction, 0, 1)) + std.substr(direction, 1, std.length(direction) - 1);
	local alertName = 'LibvirtDomainInterface' + capitalized + 'Drops';
	{
	alert: alertName,
	expr: 'increase(libvirt_domain_interface_stats_' + direction + '_drops_total[5m]) > 0',
	'for': '5m',
	labels: {
	severity: 'P3',
	},
	annotations: {
	summary: 'Libvirt: virtual machine network interface dropping ' + direction + ' packets',
	description: 'Domain {{ $labels.domain }} interface {{ $labels.target_device }} has dropped {{ $value }} ' + direction + ' packets in the last 5 minutes. Sustained packet drops can degrade tenant connectivity. Normal behavior is zero drops.',
	runbook_url: 'https://vexxhost.github.io/atmosphere/admin/monitoring.html#' + std.asciiLower(alertName),
	},
	};
	[
	dropAlert('receive'),
	dropAlert('transmit'),
	],
	local dropAlert(direction) =
	local capitalized = std.asciiUpper(std.substr(direction, 0, 1)) + std.substr(direction, 1, std.length(direction) - 1);
	local alertName = 'LibvirtDomainInterface' + capitalized + 'Drops';
	{
	alert: alertName,
	expr: 'increase(libvirt_domain_interface_stats_' + direction + '_drops_total[5m]) > 0',
	'for': '5m',
	labels: {
	severity: 'P3',
	},
	annotations: {
	summary: 'Libvirt: virtual machine network interface dropping ' + direction + ' packets',
	description: 'Domain {{ $labels.domain }} interface {{ $labels.target_device }} has dropped {{ $value }} ' + direction + ' packets in the last 5 minutes. Sustained packet drops can degrade tenant connectivity. Normal behavior is zero drops.',
	runbook_url: 'https://vexxhost.github.io/atmosphere/admin/monitoring.html#' + std.asciiLower(alertName),
	},
	};
	{
	prometheusAlerts+: {
	groups+: [
	{
	name: 'libvirt',
	rules: [
	dropAlert('receive'),
	dropAlert('transmit'),
	],