Add option to handle watchdog alerts

.github/workflows/golangci-lint.yml

@@ -17,4 +17,4 @@ jobs:
       - name: golangci-lint
         uses: golangci/golangci-lint-action@v9
         with:
-          version: v2.1.6
+          version: v2.9.0

.golangci.yml

@@ -3,7 +3,10 @@ run:
   tests: false
 linters:
   default: all
+  enable:
+    - wsl_v5
   disable:
+    - wsl
     - cyclop
     - depguard
     - err113
@@ -25,6 +28,13 @@ linters:
     - varnamelen
     - wrapcheck
     - funlen
+  settings:
+    wsl_v5:
+      allow-first-in-block: true
+      allow-whole-block: true
+      branch-max-lines: 2
+      disable:
+        - err
   exclusions:
     generated: lax
     presets:

README.md

@@ -208,6 +208,41 @@ $ check_prometheus alert --name "HostHighCpuLoad" --name "PrometheusTargetMissin
 OK - Alerts inactive | total=2 firing=0 pending=0 inactive=2
 ```
 
+#### Checking alerts via their labels
+
+The `--include-label` and `--exclude-label` options can be used to filter alerts:
+
+```bash
+$ check_prometheus alert --include-label severity=warning
+OK - 2 Alerts: 0 Firing - 0 Pending - 2 Inactive
+ \_[OK] [MysqlTooManyConnections] is inactive
+ \_[OK] [MysqlHighPreparedStatementsUtilization] is inactive
+```
+
+```bash
+$ check_prometheus alert --include-label namespace=production --exclude-label severity=info
+OK - 1 Alerts: 0 Firing - 0 Pending - 1 Inactive
+ \_[OK] [ApacheDown] is inactive
+```
+
+#### Checking watchdog alerts
+
+In Prometheus a "watchdog" or "dead man's switch" is an alert that is always firing to ensure alerting pipeline is working. The `-W, --watchdog` flag can be used to flip/negate the exit state of the plugin for these kind of alerts:
+
+```bash
+$ check_prometheus alert --name Watchdog -W --no-alerts-state 2
+[OK] - 1 Alerts: 1 Firing - 0 Pending - 0 Inactive
+\_ [OK] [Watchdog] is firing - value: 1.00 - {"alertname":"Watchdog","severity":"none"}
+|total=1 firing=1 pending=0 inactive=0
+```
+
+```bash
+$ check_prometheus alert --name Watchdog -W --no-alerts-state 2
+[CRITICAL] - 0 Alerts: 0 Firing - 0 Pending - 0 Inactive
+\_ [CRITICAL] No alerts retrieved
+|total=0 firing=0 pending=0 inactive=0
+```
+
 ## License
 
 Copyright (c) 2022 [NETWAYS GmbH](mailto:info@netways.de)

cmd/alert.go

@@ -22,6 +22,7 @@ type AlertConfig struct {
 	ExcludeLabels []string
 	IncludeLabels []string
 	ProblemsOnly  bool
+	FlipExitState bool
 	StateLabelKey string
 	NoAlertsState string
 }
@@ -99,6 +100,7 @@ inactive = 0`,
 			if cliAlertConfig.AlertName != nil {
 				check.ExitRaw(check.Unknown, "No such alert defined", "|", pdlist.String())
 			}
+
 			check.ExitRaw(noAlertsState, "No alerts defined", "|", pdlist.String())
 		}
 
@@ -163,7 +165,13 @@ inactive = 0`,
 
 				sc := result.NewPartialResult()
 
-				_ = sc.SetState(rl.GetStatus(cliAlertConfig.StateLabelKey))
+				rlStatus := rl.GetStatus(cliAlertConfig.StateLabelKey)
+				// If the negate flag is set we negate this state
+				if cliAlertConfig.FlipExitState {
+					rlStatus = negateStatus(rlStatus)
+				}
+
+				_ = sc.SetState(rlStatus)
 				sc.Output = rl.GetOutput()
 				overall.AddSubcheck(sc)
 			}
@@ -185,7 +193,13 @@ inactive = 0`,
 
 					sc := result.NewPartialResult()
 
-					_ = sc.SetState(rl.GetStatus(cliAlertConfig.StateLabelKey))
+					rlStatus := rl.GetStatus(cliAlertConfig.StateLabelKey)
+					// If the negate flag is set we negate this state
+					if cliAlertConfig.FlipExitState {
+						rlStatus = negateStatus(rlStatus)
+					}
+
+					_ = sc.SetState(rlStatus)
 					// Set the alert in the internal Type to generate the output
 					rl.Alert = alert
 					sc.Output = rl.GetOutput()
@@ -257,9 +271,12 @@ func init() {
 	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")
 
+	fs.BoolVarP(&cliAlertConfig.FlipExitState, "watchdog", "W", false,
+		"Flip the exit state for firing alerts. When this flag is set firing alerts will be OK and inactive alerts will be CRITICAL. This is intended for handling watchdog alerts")
+
 	fs.StringVarP(&cliAlertConfig.StateLabelKey, "label-key-state", "S", "",
 		"Use the given AlertRule label to override the exit state for firing alerts."+
-			"\nIf this flag is set the plugin looks for warning/critical/ok in the provided label key")
+			"\nIf this flag is set the plugin looks for the strings 'warning/critical/ok' in the provided label key")
 }
 
 // Function to convert state to integer.
@@ -314,3 +331,19 @@ func matchesLabel(labels model.LabelSet, labelsToMatch []string) bool {
 
 	return false
 }
+
+// negateStatus turns an OK state into critical and a warning/critical state into OK
+func negateStatus(state int) int {
+	switch state {
+	case check.OK:
+		return check.Critical
+	case check.Critical:
+		return check.OK
+	case check.Warning:
+		return check.OK
+	case check.Unknown:
+		return check.Unknown
+	default:
+		return check.Unknown
+	}
+}

cmd/alert_test.go

@@ -225,6 +225,15 @@ exit status 2
 			args:     []string{"run", "../main.go", "alert", "--name", "InactiveAlert"},
 			expected: "[OK] - 1 Alerts: 0 Firing - 0 Pending - 1 Inactive\n\\_ [OK] [InactiveAlert] is inactive\n|total=1 firing=0 pending=0 inactive=1\n\n",
 		},
+		{
+			name: "alert-watchdog",
+			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+				w.WriteHeader(http.StatusOK)
+				w.Write(loadTestdata(alertTestDataSet2))
+			})),
+			args:     []string{"run", "../main.go", "alert", "--name", "InactiveAlert", "-W"},
+			expected: "[CRITICAL] - 1 Alerts: 0 Firing - 0 Pending - 1 Inactive\n\\_ [CRITICAL] [InactiveAlert] is inactive\n|total=1 firing=0 pending=0 inactive=1\n\nexit status 2\n",
+		},
 		{
 			name: "alert-recording-rule",
 			server: httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {

cmd/config.go

@@ -90,6 +90,7 @@ func (c *Config) NewClient() *client.Client {
 	// Using a Bearer Token for authentication
 	if c.Bearer != "" {
 		var t = config.NewInlineSecret(c.Bearer)
+
 		rt = config.NewAuthorizationCredentialsRoundTripper("Bearer", t, rt)
 	}
 

cmd/health.go

@@ -29,6 +29,7 @@ Ready: Checks the readiness of an endpoint, which returns OK if the Prometheus s
 
 		// Creating an client and connecting to the API
 		c := cliConfig.NewClient()
+
 		err := c.Connect()
 		if err != nil {
 			check.ExitError(err)
@@ -61,6 +62,7 @@ Ready: Checks the readiness of an endpoint, which returns OK if the Prometheus s
 			if err != nil {
 				check.ExitError(err)
 			}
+
 			partialResult := result.NewPartialResult()
 
 			_ = partialResult.SetState(rc)

cmd/query.go

@@ -79,6 +79,7 @@ Note: Time range values e.G. 'go_memstats_alloc_bytes_total[0s]' only the latest
 		}
 
 		c := cliConfig.NewClient()
+
 		err = c.Connect()
 		if err != nil {
 			check.ExitError(err)
@@ -93,6 +94,7 @@ Note: Time range values e.G. 'go_memstats_alloc_bytes_total[0s]' only the latest
 			if strings.Contains(err.Error(), "unmarshalerDecoder: unexpected value type \"string\"") {
 				err = errors.New("string value results are not supported")
 			}
+
 			check.ExitError(err)
 		}
 
@@ -112,10 +114,8 @@ Note: Time range values e.G. 'go_memstats_alloc_bytes_total[0s]' only the latest
 		case model.ValVector:
 			// Instant vector - a set of time series containing a single sample for each time series, all sharing the same timestamp
 			vectorVal := result.(model.Vector)
-
 			// Set initial capacity to reduce memory allocations
 			for _, sample := range vectorVal {
-
 				numberValue := float64(sample.Value)
 				partial := goresult.NewPartialResult()
 
@@ -185,6 +185,7 @@ Note: Time range values e.G. 'go_memstats_alloc_bytes_total[0s]' only the latest
 			appendum := fmt.Sprintf("HTTP Warnings: %v", strings.Join(warnings, ", "))
 			overall.Summary = overall.GetOutput() + appendum
 		}
+
 		check.ExitRaw(overall.GetStatus(), overall.GetOutput())
 	},
 }

cmd/root.go

@@ -24,7 +24,9 @@ func Execute(version string) {
 	rootCmd.Version = version
 	rootCmd.VersionTemplate()
 
-	if err := rootCmd.Execute(); err != nil {
+	err := rootCmd.Execute()
+
+	if err != nil {
 		check.ExitError(err)
 	}
 }

internal/alert/alert.go

@@ -16,7 +16,7 @@ const (
 	alertnameLabelKey = "alertname"
 )
 
-// Internal representation of Prometheus Rules.
+// Rule is the internal representation of a Prometheus Rules.
 // Alert attribute will be used when iterating over multiple AlertingRules.
 type Rule struct {
 	AlertingRule v1.AlertingRule
@@ -139,7 +139,6 @@ func (a *Rule) GetOutput() (output string) {
 	// Add current value to output
 	value, _ = strconv.ParseFloat(a.Alert.Value, 32)
 	out.WriteString(fmt.Sprintf(" is %s - value: %.2f", a.AlertingRule.State, value))
-
 	// Add labels to the output
 	l, err := json.Marshal(a.Alert.Labels)
 

internal/client/client.go

@@ -3,6 +3,7 @@ package client
 import (
 	"context"
 	"fmt"
+	"maps"
 	"net/http"
 	"net/url"
 	"strings"
@@ -31,7 +32,6 @@ func (c *Client) Connect() error {
 		Address:      c.URL,
 		RoundTripper: c.RoundTripper,
 	})
-
 	if err != nil {
 		return fmt.Errorf("error creating client: %w", err)
 	}
@@ -113,10 +113,7 @@ func cloneRequest(r *http.Request) *http.Request {
 	r2 := new(http.Request)
 	*r2 = *r
 	// Deep copy of the Header.
-	r2.Header = make(http.Header)
-	for k, s := range r.Header {
-		r2.Header[k] = s
-	}
+	maps.Copy(r.Header, r2.Header)
 
 	return r2
 }

testdata/alertmanager/alert.rules

@@ -1,7 +1,14 @@
 groups:
 - name: Test Alerts for check_plugin
   rules:
-
+  - alert: Watchdog
+    annotations:
+      message: |
+        This is an alert meant to ensure that the entire alerting pipeline is functional.
+        This alert is always firing.
+    expr: vector(1)
+    labels:
+      severity: none
   - alert: PrometheusTargetMissing
     expr: up == 0
     for: 0m