- Run a simple webhook receiver which outputs the alerts received to the log output
- Configure a custom Alert in Prometheus
- Configure a new receiver in AlertManager to handle the alert and send it to a webhook
$ oc apply -f kubernetes_manifests/webhook-deployment.yaml
deployment.apps/my-webhook created
service/my-webhook createdThis runs the webhook receiver in Openshift.
The code is in webhook-receiver.go. It's a simple webserver exposing an
endpoint /webhook and listening on port 8080.
It leverages the AlertManager's
template module.
More precisely, the Data struct can be used to parse the alerts.
The webhook simply outputs information about the alerts to stdout every time a POST request is received.
You can edit the code and build your own image by adapting the following commands:
$ export QUAY_USERNAME="username"
$ docker build quay.io/$QUAY_USERNAME/my-demo-webhook:0.0.1
$ docker push quay.io/$QUAY_USERNAME=/my-demo-webhook:0.0.1
$ sed -e "s/quay.io\/mgoerens\/demo-webhook-receiver-alertmanager.*$/quay.io\/$QUAY_USERNAME\/my-demo-webhook:0.0.1/g" kubernetes_manifests/webhook-deployment.yaml Using:
$ oc version
Client Version: 4.8.2
Server Version: 4.8.0-fc.6
Kubernetes Version: v1.21.0-rc.0+fc33082$ oc -n openshift-user-workload-monitoring get pod
No resources found in openshift-user-workload-monitoring namespace.
$ oc -n openshift-monitoring apply -f kubernetes_manifests/cluster-monitoring-config.yaml
configmap/cluster-monitoring-config created
$ oc -n openshift-user-workload-monitoring get pod
NAME READY STATUS RESTARTS AGE
prometheus-operator-6b56db9975-zbpf8 2/2 Running 0 12s
prometheus-user-workload-0 5/5 Running 1 9s
prometheus-user-workload-1 5/5 Running 1 9s
thanos-ruler-user-workload-0 3/3 Running 0 5s
thanos-ruler-user-workload-1 3/3 Running 0 5s$ oc apply -f kubernetes_manifests/prometheus-rule.yaml
prometheusrule.monitoring.coreos.com/example-alert createdThe alert is now visible in the OpenShift console under "Monitoring/Alerting"
in the "AlertRules" tab. Clear all filters, then filter per "Source/User".
Their should be only 1 alert rule called ExampleAlert in Firing state.
In the "Alerts" tab, the ExampleAlert should also appear as it's in Firing
state.
Get the Cluster IP of the webhook service:
$ oc get svc my-webhook
NAME TYPE CLUSTER-IP EXTERNAL-IP PORT(S) AGE
my-webhook NodePort 172.30.188.12 <none> 8080:31635/TCP 2d16hIn the OpenShift console, under "Administration/Cluster Settings", in the "Global Configuration" tab, click "AlertManager" then "Create Receiver":
- Receiver Name: "my-webhook"
- Receiver Type: "Webhook"
- URL: "http://172.30.188.12:8080/webhook"
- Routing labels:
- Name: "app"
- Value: "my-webhook"
$ export POD_NAME=`oc get po | awk '$1 ~ /my-webhook-/ {print $1}'`
$ oc logs -f $POD_NAME
2021/08/06 16:09:26 listening on: :8080
For debugging purposed, one can speed up the frequency of alerts being sent
with the Repeat Interval and Group Interval in the AlertManager config:
By default, only the first receiver matching the alert's labels is sending the alert. Check the Receivers configuration, and espcially make sure there are no other Receiver already catching the alert.
Every alert enters the routing tree at the configured top-level route, which
must match all alerts (i.e. not have any configured matchers). It then
traverses the child nodes. If continue is set to false, it stops after the
first matching child. If continue is true on a matching node, the alert will
continue matching against subsequent siblings. If an alert does not match any
children of a node (no matching child nodes, or none exist), the alert is
handled based on the configuration parameters of the current node.
See https://prometheus.io/docs/alerting/latest/configuration/#route
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