documentation/prometheus-mixin: improve PrometheusNotIngestingSamples
The alert shouldn't fire when there's no target and no rule configured.
{
alert: 'PrometheusNotIngestingSamples',
expr: |||
+ (
rate(prometheus_tsdb_head_samples_appended_total{%(prometheusSelector)s}[5m]) <= 0
+ and
+ (
+ sum without(scrape_job) (prometheus_target_metadata_cache_entries{%(prometheusSelector)s}) > 0
+ or
+ sum without(rule_group) (prometheus_rule_group_rules{%(prometheusSelector)s}) > 0
+ )
+ )
||| % $._config,
'for': '10m',
labels: {
