Rework logic when there are no alerts defined

Changes default to OK, instead of UNKNOWN.

Added a check to see if the API response contains
alert rules. If not, we exit early.

To add extra flexibility this also adds a --no-alerts-state
flag that can be used to set the desired exit state when no
alerts are found.

README.md

@@ -150,11 +150,12 @@ 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
- -P, --problems       Display only alerts which status is not inactive/OK
+  -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

@@ -1,7 +1,9 @@
 package cmd
 
 import (
+	"errors"
 	"fmt"
+	"strings"
 
 	"github.com/NETWAYS/check_prometheus/internal/alert"
 	"github.com/NETWAYS/go-check"
@@ -10,6 +12,15 @@ import (
 	"github.com/spf13/cobra"
 )
 
+type AlertConfig struct {
+	AlertName     []string
+	Group         []string
+	ProblemsOnly  bool
+	NoAlertsState string
+}
+
+var cliAlertConfig AlertConfig
+
 func contains(s string, list []string) bool {
 	// Tiny helper to see if a string is in a list of strings
 	for _, elem := range list {
@@ -40,14 +51,21 @@ inactive = 0`,
 	 \_[CRITICAL] [PrometheusAlertmanagerJobMissing] - Job: [alertmanager] is firing - value: 1.00
 	 | total=2 firing=1 pending=0 inactive=1`,
 	Run: func(_ *cobra.Command, _ []string) {
+		// Convert --no-alerts-state to integer and validate input
+		noAlertsState, err := convertStateToInt(cliAlertConfig.NoAlertsState)
+		if err != nil {
+			check.ExitError(fmt.Errorf("invalid value for --no-alerts-state: %s", cliAlertConfig.NoAlertsState))
+		}
+
 		var (
 			counterFiring   int
 			counterPending  int
 			counterInactive int
 		)
 
 		c := cliConfig.NewClient()
-		err := c.Connect()
+		err = c.Connect()
+
 		if err != nil {
 			check.ExitError(err)
 		}
@@ -65,6 +83,16 @@ inactive = 0`,
 		// Get all rules from all groups into a single list
 		rules := alert.FlattenRules(alerts.Groups)
 
+		// If there are no rules we can exit early
+		if len(rules) == 0 {
+			// Since the user is expecting the state of a certain alert and
+			// it that is not present it might be noteworthy.
+			if cliAlertConfig.AlertName != nil {
+				check.ExitRaw(check.Unknown, "No such alert defined")
+			}
+			check.ExitRaw(noAlertsState, "No alerts defined")
+		}
+
 		// Set initial capacity to reduce memory allocations
 		var l int
 		for _, rl := range rules {
@@ -164,11 +192,33 @@ inactive = 0`,
 
 func init() {
 	rootCmd.AddCommand(alertCmd)
+
 	fs := alertCmd.Flags()
+
+	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.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'"+
 			"\nIf no name is given, all alerts will be evaluated")
+
 	fs.BoolVarP(&cliAlertConfig.ProblemsOnly, "problems", "P", false,
 		"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")
 }
+
+// Function to convert state to integer.
+func convertStateToInt(state string) (int, error) {
+	state = strings.ToUpper(state)
+	switch state {
+	case "OK", "0":
+		return check.OK, nil
+	case "WARNING", "1":
+		return check.Warning, nil
+	case "CRITICAL", "2":
+		return check.Critical, nil
+	case "UNKNOWN", "3":
+		return check.Unknown, nil
+	default:
+		return check.Unknown, errors.New("invalid state")
+	}
+}

cmd/alert_test.go

@@ -38,7 +38,7 @@ func TestAlertCmd(t *testing.T) {
 				w.Write([]byte(`{"status":"success","data":{"groups":[]}}`))
 			})),
 			args:     []string{"run", "../main.go", "alert"},
-			expected: "[UNKNOWN] - 0 Alerts: 0 Firing - 0 Pending - 0 Inactive\n\nexit status 3\n",
+			expected: "[OK] - No alerts defined\n",
 		},
 		{
 			name: "alert-none-with-problems",
@@ -47,7 +47,25 @@ func TestAlertCmd(t *testing.T) {
 				w.Write([]byte(`{"status":"success","data":{"groups":[]}}`))
 			})),
 			args:     []string{"run", "../main.go", "alert", "--problems"},
-			expected: "[UNKNOWN] - 0 Alerts: 0 Firing - 0 Pending - 0 Inactive\n\nexit status 3\n",
+			expected: "[OK] - No alerts defined\n",
+		},
+		{
+			name: "alert-none-with-no-state",
+			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+				w.Write([]byte(`{"status":"success","data":{"groups":[]}}`))
+			})),
+			args:     []string{"run", "../main.go", "alert", "--no-alerts-state", "3"},
+			expected: "[UNKNOWN] - No alerts defined\nexit status 3\n",
+		},
+		{
+			name: "alert-none-with-name",
+			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+				w.Write([]byte(`{"status":"success","data":{"groups":[]}}`))
+			})),
+			args:     []string{"run", "../main.go", "alert", "--name", "MyPreciousAlert"},
+			expected: "[UNKNOWN] - No such alert defined\nexit status 3\n",
 		},
 		{
 			name: "alert-default",

cmd/config.go

@@ -15,12 +15,6 @@ import (
 	"github.com/prometheus/common/config"
 )
 
-type AlertConfig struct {
-	AlertName    []string
-	Group        []string
-	ProblemsOnly bool
-}
-
 type Config struct {
 	BasicAuth string `env:"CHECK_PROMETHEUS_BASICAUTH"`
 	Bearer    string `env:"CHECK_PROMETHEUS_BEARER"`
@@ -57,10 +51,7 @@ You should have received a copy of the GNU General Public License
 along with this program. If not, see https://www.gnu.org/licenses/.
 `
 
-var (
-	cliConfig      Config
-	cliAlertConfig AlertConfig
-)
+var cliConfig Config
 
 func (c *Config) NewClient() *client.Client {
 	u := url.URL{