Created attachment 1594510 [details]
Alerts are marked as "Not grouped"

Description of problem:
Watchdog alert is under general.rules group, but in the Alertmanager web console, it is under "Not grouped" , same for other alerts .see the attached picture.

$ oc -n openshift-monitoring logs -c alertmanager alertmanager-main-0
level=info ts=2019-07-29T06:03:41.221Z caller=main.go:197 msg="Starting Alertmanager" version="(version=0.18.0, branch=rhaos-4.2-rhel-7, revision=38c47ef01d3959ca8c72e6c6fc892e3e8fcf8957)"
level=info ts=2019-07-29T06:03:41.221Z caller=main.go:198 build_context="(go=go1.12.6, user=root@8c461faab7bf, date=20190728-18:37:04)"
level=warn ts=2019-07-29T06:03:42.164Z caller=cluster.go:228 component=cluster msg="failed to join cluster" err="3 errors occurred:\n\t* Failed to resolve alertmanager-main-0.alertmanager-operated.openshift-monitoring.svc:9094: lookup alertmanager-main-0.alertmanager-operated.openshift-monitoring.svc on 172.30.0.10:53: no such host\n\t* Failed to resolve alertmanager-main-1.alertmanager-operated.openshift-monitoring.svc:9094: lookup alertmanager-main-1.alertmanager-operated.openshift-monitoring.svc on 172.30.0.10:53: no such host\n\t* Failed to resolve alertmanager-main-2.alertmanager-operated.openshift-monitoring.svc:9094: lookup alertmanager-main-2.alertmanager-operated.openshift-monitoring.svc on 172.30.0.10:53: no such host\n\n"
level=info ts=2019-07-29T06:03:42.164Z caller=cluster.go:230 component=cluster msg="will retry joining cluster every 10s"
level=warn ts=2019-07-29T06:03:42.165Z caller=main.go:287 msg="unable to join gossip mesh" err="3 errors occurred:\n\t* Failed to resolve alertmanager-main-0.alertmanager-operated.openshift-monitoring.svc:9094: lookup alertmanager-main-0.alertmanager-operated.openshift-monitoring.svc on 172.30.0.10:53: no such host\n\t* Failed to resolve alertmanager-main-1.alertmanager-operated.openshift-monitoring.svc:9094: lookup alertmanager-main-1.alertmanager-operated.openshift-monitoring.svc on 172.30.0.10:53: no such host\n\t* Failed to resolve alertmanager-main-2.alertmanager-operated.openshift-monitoring.svc:9094: lookup alertmanager-main-2.alertmanager-operated.openshift-monitoring.svc on 172.30.0.10:53: no such host\n\n"
level=info ts=2019-07-29T06:03:42.165Z caller=cluster.go:623 component=cluster msg="Waiting for gossip to settle..." interval=2s
level=info ts=2019-07-29T06:03:42.197Z caller=coordinator.go:119 component=configuration msg="Loading configuration file" file=/etc/alertmanager/config/alertmanager.yaml
level=info ts=2019-07-29T06:03:42.198Z caller=coordinator.go:131 component=configuration msg="Completed loading of configuration file" file=/etc/alertmanager/config/alertmanager.yaml
level=info ts=2019-07-29T06:03:42.202Z caller=main.go:429 msg=Listening address=127.0.0.1:9093
level=info ts=2019-07-29T06:03:44.165Z caller=cluster.go:648 component=cluster msg="gossip not settled" polls=0 before=0 now=1 elapsed=2.000656524s
level=info ts=2019-07-29T06:03:52.166Z caller=cluster.go:640 component=cluster msg="gossip settled; proceeding" elapsed=10.00149921s


Version-Release number of selected component (if applicable):
4.2.0-0.nightly-2019-07-28-222114

How reproducible:
Always

Steps to Reproduce:
1. Check alerts in Alertmanager web console
2.
3.

Actual results:
Alerts are marked as "Not grouped" in Alertmanager web console

Expected results:


Additional info: