Example with option to modify alert thresholds

Review comment: https://github.com/coreos/kube-prometheus/pull/425#discussion_r387494885

docs/weave-net-support.md

@@ -13,18 +13,49 @@ Using kube-prometheus and kubectl you will be able install the following for mon
 5. [Grafana Dashboard for WeaveNet(Cluster)](https://grafana.com/grafana/dashboards/11789) This will setup the cluster level monitoring for weave net.
 
 ## Instructions
-- You can monitor weave-net CNI using kube-prometheus with:
+- You can monitor weave-net CNI using an example like below. **Please note that some alert configurations are environment specific and may require modifications of alert thresholds**. For example: The FastDP flows have never gone below 1500 for us. But if this value is say 2000 for you then you can use an example like below to update the alert. The alerts which may require threshold modifications are `WeaveNetFastDPFlowsLow` and `WeaveNetIPAMUnreachable`.
+
 [embedmd]:# (../examples/weavenet-example.jsonnet)
 ```jsonnet
 local kp =  (import 'kube-prometheus/kube-prometheus.libsonnet') +
-            (import 'kube-prometheus/kube-prometheus-weavenet.libsonnet');
+            (import 'kube-prometheus/kube-prometheus-weavenet.libsonnet') + {
+  _config+:: {
+    namespace: 'monitoring',
+  },
+  prometheusAlerts+:: {
+    groups: std.map(
+      function(group)
+        if group.name == 'weave-net' then
+          group {
+            rules: std.map(function(rule)
+              if rule.alert == "WeaveNetFastDPFlowsLow" then
+                rule {
+                  expr: "sum(weave_flows) < 2000"
+                }
+              else if rule.alert == "WeaveNetIPAMUnreachable" then
+                rule {
+                  expr: "weave_ipam_unreachable_percentage > 25"
+                }
+              else
+                rule
+              ,
+              group.rules
+            )
+          }
+        else
+          group,
+        super.groups
+      ),
+  },
+};
 
 { ['00namespace-' + name]: kp.kubePrometheus[name] for name in std.objectFields(kp.kubePrometheus) } +
 { ['0prometheus-operator-' + name]: kp.prometheusOperator[name] for name in std.objectFields(kp.prometheusOperator) } +
 { ['node-exporter-' + name]: kp.nodeExporter[name] for name in std.objectFields(kp.nodeExporter) } +
 { ['kube-state-metrics-' + name]: kp.kubeStateMetrics[name] for name in std.objectFields(kp.kubeStateMetrics) } +
 { ['prometheus-' + name]: kp.prometheus[name] for name in std.objectFields(kp.prometheus) } +
-{ ['prometheus-adapter-' + name]: kp.prometheusAdapter[name] for name in std.objectFields(kp.prometheusAdapter) }
+{ ['prometheus-adapter-' + name]: kp.prometheusAdapter[name] for name in std.objectFields(kp.prometheusAdapter) } +
+{ ['grafana-' + name]: kp.grafana[name] for name in std.objectFields(kp.grafana) }
 ```
 
 - After you have the required yamls file please run

examples/weavenet-example.jsonnet

 local kp =  (import 'kube-prometheus/kube-prometheus.libsonnet') +
-            (import 'kube-prometheus/kube-prometheus-weavenet.libsonnet');
+            (import 'kube-prometheus/kube-prometheus-weavenet.libsonnet') + {
+  _config+:: {
+    namespace: 'monitoring',
+  },
+  prometheusAlerts+:: {
+    groups: std.map(
+      function(group)
+        if group.name == 'weave-net' then
+          group {
+            rules: std.map(function(rule)
+              if rule.alert == "WeaveNetFastDPFlowsLow" then
+                rule {
+                  expr: "sum(weave_flows) < 2000"
+                }
+              else if rule.alert == "WeaveNetIPAMUnreachable" then
+                rule {
+                  expr: "weave_ipam_unreachable_percentage > 25"
+                }
+              else
+                rule
+              ,
+              group.rules
+            )
+          }
+        else
+          group,
+        super.groups
+      ),
+  },
+};
 
 { ['00namespace-' + name]: kp.kubePrometheus[name] for name in std.objectFields(kp.kubePrometheus) } +
 { ['0prometheus-operator-' + name]: kp.prometheusOperator[name] for name in std.objectFields(kp.prometheusOperator) } +
 { ['node-exporter-' + name]: kp.nodeExporter[name] for name in std.objectFields(kp.nodeExporter) } +
 { ['kube-state-metrics-' + name]: kp.kubeStateMetrics[name] for name in std.objectFields(kp.kubeStateMetrics) } +
 { ['prometheus-' + name]: kp.prometheus[name] for name in std.objectFields(kp.prometheus) } +
-{ ['prometheus-adapter-' + name]: kp.prometheusAdapter[name] for name in std.objectFields(kp.prometheusAdapter) }
+{ ['prometheus-adapter-' + name]: kp.prometheusAdapter[name] for name in std.objectFields(kp.prometheusAdapter) } +
+{ ['grafana-' + name]: kp.grafana[name] for name in std.objectFields(kp.grafana) }