title: promethues operator alertmanager-main-0 pending and display
body: <p><strong>What happened?</strong>
  kubernetes version: 1.12
  promethus operator: release-0.1
  I follow the README:</p>
  
  <pre><code>$ kubectl create -f manifests/
  
  # It can take a few seconds for the above 'create manifests' command to fully create the following resources, so verify the resources are ready before proceeding.
  $ until kubectl get customresourcedefinitions servicemonitors.monitoring.coreos.com ; do date; sleep 1; echo ""; done
  $ until kubectl get servicemonitors --all-namespaces ; do date; sleep 1; echo ""; done
  
  $ kubectl apply -f manifests/ # This command sometimes may need to be done twice (to workaround a race condition).
  </code></pre>
  
  <p>and then I use the command and then is showed like:</p>
  
  <pre><code>[root@VM_8_3_centos /data/hansenwu/kube-prometheus/manifests]# kubectl get pod -n monitoring
  NAME                                  READY   STATUS    RESTARTS   AGE
  alertmanager-main-0                   2/2     Running   0          66s
  alertmanager-main-1                   1/2     Running   0          47s
  grafana-54f84fdf45-kt2j9              1/1     Running   0          72s
  kube-state-metrics-65b8dbf498-h7d8g   4/4     Running   0          57s
  node-exporter-7mpjw                   2/2     Running   0          72s
  node-exporter-crfgv                   2/2     Running   0          72s
  node-exporter-l7s9g                   2/2     Running   0          72s
  node-exporter-lqpns                   2/2     Running   0          72s
  prometheus-adapter-5b6f856dbc-ndfwl   1/1     Running   0          72s
  prometheus-k8s-0                      3/3     Running   1          59s
  prometheus-k8s-1                      3/3     Running   1          59s
  prometheus-operator-5c64c8969-lqvkb   1/1     Running   0          72s
  [root@VM_8_3_centos /data/hansenwu/kube-prometheus/manifests]# kubectl get pod -n monitoring
  NAME                                  READY   STATUS    RESTARTS   AGE
  alertmanager-main-0                   0/2     Pending   0          0s
  grafana-54f84fdf45-kt2j9              1/1     Running   0          75s
  kube-state-metrics-65b8dbf498-h7d8g   4/4     Running   0          60s
  node-exporter-7mpjw                   2/2     Running   0          75s
  node-exporter-crfgv                   2/2     Running   0          75s
  node-exporter-l7s9g                   2/2     Running   0          75s
  node-exporter-lqpns                   2/2     Running   0          75s
  prometheus-adapter-5b6f856dbc-ndfwl   1/1     Running   0          75s
  prometheus-k8s-0                      3/3     Running   1          62s
  prometheus-k8s-1                      3/3     Running   1          62s
  prometheus-operator-5c64c8969-lqvkb   1/1     Running   0          75s
  
  </code></pre>
  
  <p>I don't know why the pod  altertmanager-main-0 pending and disaply then restart.
  And I see the event, it is showed as:</p>
  
  <pre><code>72s         Warning   FailedCreate             StatefulSet   create Pod alertmanager-main-0 in StatefulSet alertmanager-main failed error: The POST operation against Pod could not be completed at this time, please try again.
  72s         Warning   FailedCreate             StatefulSet   create Pod alertmanager-main-0 in StatefulSet alertmanager-main failed error: The POST operation against Pod could not be completed at this time, please try again.
  72s         Warning^Z   FailedCreate             StatefulSet
  [10]+  Stopped                 kubectl get events -n monitoring
  </code></pre>