Add parameter alerts.excludeNamespaces to exclude specific namespac…

…es from base alerts

This allows us to exclude specific namespaces which are included
through regex patterns in `alerts.includeNamespaces`, for example when
customers install and manage an OpenShift 4 component themselves.

class/defaults.yml

@@ -116,6 +116,7 @@ parameters:
         - kube-.*
         - openshift-.*
         - syn.*
+      excludeNamespaces: []
       ignoreNames:
         - AlertmanagerReceiversNotConfigured
         - CannotRetrieveUpdates

component/rules.jsonnet

@@ -130,11 +130,30 @@ local annotateRules = {
 local renderedNamespaceSelector =
   std.join('|', com.renderArray(params.alerts.includeNamespaces));
 
+local renderedExcludesSelector =
+  std.join('|', com.renderArray(params.alerts.excludeNamespaces));
+
+local renderedSelector =
+  local hasNsSel = std.length(renderedNamespaceSelector) > 0;
+  local hasExcSel = std.length(renderedExcludesSelector) > 0;
+  (
+    if hasNsSel then
+      'namespace=~"(%s)"' % renderedNamespaceSelector
+    else ''
+
+  ) + (
+    if hasNsSel && hasExcSel then ',' else ''
+  ) + (
+    if std.length(renderedExcludesSelector) > 0 then
+      'namespace!~"(%s)"' % renderedExcludesSelector
+    else ''
+  );
+
 local patchExpr(expr) =
   std.strReplace(
     expr,
     'namespace=~"(openshift-.*|kube-.*|default)"',
-    'namespace=~"(%s)"' % renderedNamespaceSelector
+    renderedSelector
   );
 
 local rulePatches =

docs/modules/ROOT/pages/references/parameters.adoc

@@ -353,7 +353,7 @@ default:: https://github.com/appuio/component-openshift4-monitoring/blob/master/
 
 List of namespace patterns to use for alerts which have `namespace=~"(openshift-.\*|kube-.*|default)"` in the upstream rule.
 The component generates a regex pattern from the list by concatenating all elements into a large OR-regex.
-To inject the custom regex, the component searches for the exact string `namespace=~"(openshift-.\*|kube-.*|default)"` in field `expr` of each alert rule and replaces it with the regex generated from the parameter.
+To inject the custom regex, the component searches for the exact string `namespace=~"(openshift-.\*|kube-.*|default)"` in field `expr` of each alert rule and replaces it with the regex generated from this parameter and parameter `excludeNamespaces`.
 
 The component processes the list with `com.renderArray()` to allow users to drop entries in the hierarchy.
 
@@ -372,6 +372,36 @@ includeNamespaces:
 
 The component will generate namespace selector `namespace=~"(default|syn.*)"` from this input configuration.
 
+=== `excludeNamespaces`
+
+[horizontal]
+type:: list
+default:: `[]`
+
+List of namespace patterns to exclude for alerts which have `namespace=~"(openshift-.\*|kube-.*|default)"` in the upstream rule.
+The component generates a regex pattern from the list by concatenating all elements into a large OR-regex.
+To inject the custom regex, the component searches for the exact string `namespace=~"(openshift-.\*|kube-.*|default)"` in field `expr` of each alert rule and replaces it with the regex generated from this parameter and parameter `includeNamespaces`.
+
+The component processes the list with `com.renderArray()` to allow users to drop entries in the hierarchy.
+
+IMPORTANT: The component doesn't validate that the list entries are valid regex patterns.
+
+==== Example
+
+We assume that the input config has patterns `default` and `openshift.*` and `syn.*` for `includeNamespaces` and `openshift-adp` for `excludeNamespaces`:
+
+[source,yaml]
+----
+includeNamespaces:
+  - default
+  - openshift.*
+  - syn.*
+excludeNamespaces:
+  - openshift-adp
+----
+
+The component will generate namespace selector `namespace=~"(default|openshift.*|syn.*)",namespace!~"(openshift-adp)"` from this input configuration.
+
 === `ignoreNames`
 
 [horizontal]

tests/custom-rules.yml

@@ -14,6 +14,8 @@ parameters:
     manifests_version: release-4.13
 
     alerts:
+      excludeNamespaces:
+        - openshift-adp
       patchRules:
         '*':
           HighOverallControlPlaneMemory: