A resolved notification is not sent when a single alert within in a group of alerts is resolved

[Srinivas Anant]

Hi Prometheus team,

I have two alerts under a particular group, when they are in alert state, alertmanager sends me an alert for both of them but if one of the alert in the particular group is resolved I don’t get the resolved alert for that and if the second alert that is resolved I immediately get the alert for the same.

Example:

• Service-A down, Service-B down --> Both service’s down, sends notification to slack channel
• Service-A up, Service-B down —> Service-B down alert (no resolved alert for service-A)
• Service-A up, Service-B up --> Resolved alert for Service-B (no resolved alert for service-A)

alertmanager.yml

route:

  group_by: ['alertname']

  group_wait: 1m

  group_interval: 5m

  repeat_interval: 5m

  receiver: demo-channel

receivers:

- name: demo-channel

  slack_configs:

  - api_url: 'webhook_url'

    channel: '#alerts'

    title: "alert"

    text: "{{ range .Alerts }}\n  {{ .Annotations.summary }}\n {{ end }}"

    send_resolved: true

Alertmanager details:

Branch: HEAD
BuildDate: 20190503-09:10:07
BuildUser: root@932a86a52b76
GoVersion:go1.12.4
Revision: c7551cd75c414dc81df027f691e2eb21d4fd85b2
Version: 0.17.0

Prometheus details:

Version: 2.9.2
Revision: d3245f15022551c6fc8281766ea62db4d71e2747
Branch: HEAD
BuildUser: root@1d43b6951e8f
BuildDate: 20190424-15:32:31
GoVersion: go1.12.4

Thanks,
Anant