Add option to exclude alerts from the results

The use case behind this: sometimes you want to define
a so called Watchdog or DeadMansSwitch alert that is always
firing, in order to monitoring that the alerting is working.

When such a Watchdog is defined the list of all alerts will
always be Critical. Thus we add a flag to exclude certain alerts.

README.md

@@ -150,12 +150,13 @@ Examples:
    | total=2 firing=1 pending=0 inactive=1
 
 Flags:
-  -h, --help                     help for alert
-  -n, --name strings             The name of one or more specific alerts to check.
-                                 This parameter can be repeated e.G.: '--name alert1 --name alert2'
-                                 If no name is given, all alerts will be evaluated
-  -T, --no-alerts-state string   State to assign when no alerts are found (0, 1, 2, 3, OK, WARNING, CRITICAL, UNKNOWN). If not set this defaults to OK (default "OK")
-  -P, --problems                 Display only alerts which status is not inactive/OK. Note that in combination with the --name flag this might result in no alerts being displayed
+      --exclude-alert stringArray  Alerts to ignore. Can be used multiple times and supports regex.
+  -h, --help                       help for alert
+  -n, --name strings               The name of one or more specific alerts to check.
+                                   This parameter can be repeated e.G.: '--name alert1 --name alert2'
+                                   If no name is given, all alerts will be evaluated
+  -T, --no-alerts-state string     State to assign when no alerts are found (0, 1, 2, 3, OK, WARNING, CRITICAL, UNKNOWN). If not set this defaults to OK (default "OK")
+  -P, --problems                   Display only alerts which status is not inactive/OK. Note that in combination with the --name flag this might result in no alerts being displayed
 ```
 
 #### Checking all defined alerts

cmd/alert.go

@@ -3,6 +3,7 @@ package cmd
 import (
 	"errors"
 	"fmt"
+	"regexp"
 	"strings"
 
 	"github.com/NETWAYS/check_prometheus/internal/alert"
@@ -15,6 +16,7 @@ import (
 type AlertConfig struct {
 	AlertName     []string
 	Group         []string
+	ExcludeAlerts []string
 	ProblemsOnly  bool
 	NoAlertsState string
 }
@@ -115,6 +117,17 @@ inactive = 0`,
 				continue
 			}
 
+			alertMatched, regexErr := matches(rl.AlertingRule.Name, cliAlertConfig.ExcludeAlerts)
+
+			if regexErr != nil {
+				check.ExitRaw(check.Unknown, "Invalid regular expression provided:", regexErr.Error())
+			}
+
+			if alertMatched {
+				// If the alert matches a regex from the list we can skip it.
+				continue
+			}
+
 			// Handle Inactive Alerts
 			if len(rl.AlertingRule.Alerts) == 0 {
 				// Counting states for perfdata
@@ -197,6 +210,8 @@ func init() {
 
 	fs.StringVarP(&cliAlertConfig.NoAlertsState, "no-alerts-state", "T", "OK", "State to assign when no alerts are found (0, 1, 2, 3, OK, WARNING, CRITICAL, UNKNOWN). If not set this defaults to OK")
 
+	fs.StringArrayVar(&cliAlertConfig.ExcludeAlerts, "exclude-alert", []string{}, "Alerts to ignore. Can be used multiple times and supports regex.")
+
 	fs.StringSliceVarP(&cliAlertConfig.AlertName, "name", "n", nil,
 		"The name of one or more specific alerts to check."+
 			"\nThis parameter can be repeated e.G.: '--name alert1 --name alert2'"+
@@ -222,3 +237,20 @@ func convertStateToInt(state string) (int, error) {
 		return check.Unknown, errors.New("invalid state")
 	}
 }
+
+// Matches a list of regular expressions against a string.
+func matches(input string, regexToExclude []string) (bool, error) {
+	for _, regex := range regexToExclude {
+		re, err := regexp.Compile(regex)
+
+		if err != nil {
+			return false, err
+		}
+
+		if re.MatchString(input) {
+			return true, nil
+		}
+	}
+
+	return false, nil
+}

cmd/alert_test.go

@@ -98,6 +98,28 @@ exit status 2
 exit status 2
 `,
 		},
+		{
+			name: "alert-problems-only-with-exlude",
+			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+				w.Write([]byte(`{"status":"success","data":{"groups":[{"name":"Foo","file":"alerts.yaml","rules":[{"state":"inactive","name":"HostOutOfMemory","query":"up","duration":120,"labels":{"severity":"critical"},"annotations":{"description":"Foo","summary":"Foo"},"alerts":[],"health":"ok","evaluationTime":0.000553928,"lastEvaluation":"2022-11-24T14:08:17.597083058Z","type":"alerting"}],"interval":10,"limit":0,"evaluationTime":0.000581212,"lastEvaluation":"2022-11-24T14:08:17.59706083Z"},{"name":"SQL","file":"alerts.yaml","rules":[{"state":"pending","name":"SqlAccessDeniedRate","query":"mysql","duration":17280000,"labels":{"severity":"warning"},"annotations":{"description":"MySQL","summary":"MySQL"},"alerts":[{"labels":{"alertname":"SqlAccessDeniedRate","instance":"localhost","job":"mysql","severity":"warning"},"annotations":{"description":"MySQL","summary":"MySQL"},"state":"pending","activeAt":"2022-11-21T10:38:35.373483748Z","value":"4.03448275862069e-01"}],"health":"ok","evaluationTime":0.002909617,"lastEvaluation":"2022-11-24T14:08:25.375220595Z","type":"alerting"}],"interval":10,"limit":0,"evaluationTime":0.003046259,"lastEvaluation":"2022-11-24T14:08:25.375096825Z"},{"name":"TLS","file":"alerts.yaml","rules":[{"state":"firing","name":"BlackboxTLS","query":"SSL","duration":0,"labels":{"severity":"critical"},"annotations":{"description":"TLS","summary":"TLS"},"alerts":[{"labels":{"alertname":"TLS","instance":"https://localhost:443","job":"blackbox","severity":"critical"},"annotations":{"description":"TLS","summary":"TLS"},"state":"firing","activeAt":"2022-11-24T05:11:27.211699259Z","value":"-6.065338210999966e+06"}],"health":"ok","evaluationTime":0.000713955,"lastEvaluation":"2022-11-24T14:08:17.212720815Z","type":"alerting"}],"interval":10,"limit":0,"evaluationTime":0.000738927,"lastEvaluation":"2022-11-24T14:08:17.212700182Z"}]}}`))
+			})),
+			args: []string{"run", "../main.go", "alert", "--problems", "--exclude-alert", "Sql.*DeniedRate"},
+			expected: `[CRITICAL] - 1 Alerts: 1 Firing - 0 Pending - 0 Inactive
+\_ [CRITICAL] [BlackboxTLS] - Job: [blackbox] on Instance: [https://localhost:443] is firing - value: -6065338.00
+
+exit status 2
+`,
+		},
+		{
+			name: "alert-with-exclude-error",
+			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+				w.Write([]byte(`{"status":"success","data":{"groups":[{"name":"k8s","file":"/etc/prometheus/rules/al.yaml","rules":[{"state":"inactive","name":"NodeHasMemoryPressure","query":"kube_node{condition=\"MemoryPressure\",status=\"true\"} == 1","duration":300,"keepFiringFor":0,"labels":{},"annotations":{"summary":"Memory pressure on instance {{ $labels.instance }}"},"alerts":[],"health":"ok","evaluationTime":0.00023339,"lastEvaluation":"2024-12-18T17:50:01.483161228Z","type":"alerting"}],"interval":15,"limit":0,"evaluationTime":0.000262616,"lastEvaluation":"2024-12-18T17:50:01.483135426Z"},{"name":"example","file":"/etc/prometheus/rules/rec.yaml","rules":[{"name":"rule:prometheus_http_requests_total:sum","query":"sum by (code) (rate(prometheus_http_requests_total[5m]))","health":"ok","evaluationTime":0.000472562,"lastEvaluation":"2024-12-18T17:50:12.420737469Z","type":"recording"}],"interval":15,"limit":0,"evaluationTime":0.000497618,"lastEvaluation":"2024-12-18T17:50:12.42071533Z"}],"groupNextToken:omitempty":""}}`))
+			})),
+			args:     []string{"run", "../main.go", "alert", "--exclude-alert", "[a-z"},
+			expected: "[UNKNOWN] - Invalid regular expression provided: error parsing regexp: missing closing ]: `[a-z`\nexit status 3\n",
+		},
 		{
 			name: "alert-no-such-alert",
 			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {