Alerting: Add command line parsing for historian options (#114865)

apps/alerting/historian/go.mod

@@ -9,6 +9,7 @@ require (
 	github.com/grafana/grafana-app-sdk v0.48.4
 	github.com/grafana/grafana-app-sdk/logging v0.48.3
 	github.com/prometheus/client_golang v1.23.2
+	github.com/spf13/pflag v1.0.10
 	github.com/stretchr/testify v1.11.1
 	go.opentelemetry.io/otel v1.38.0
 	go.opentelemetry.io/otel/trace v1.38.0
@@ -113,7 +114,6 @@ require (
 	github.com/shurcooL/httpfs v0.0.0-20230704072500-f1e31cf0ba5c // indirect
 	github.com/shurcooL/vfsgen v0.0.0-20230704071429-0000e147ea92 // indirect
 	github.com/spf13/cast v1.10.0 // indirect
-	github.com/spf13/pflag v1.0.10 // indirect
 	github.com/stretchr/objx v0.5.2 // indirect
 	github.com/uber/jaeger-client-go v2.30.0+incompatible // indirect
 	github.com/uber/jaeger-lib v2.4.1+incompatible // indirect

apps/alerting/historian/pkg/app/config/config.go

@@ -1,10 +1,20 @@
 package config
 
 import (
+	"net/url"
+	"time"
+
+	"github.com/spf13/pflag"
+
 	"github.com/grafana/alerting/notify/historian/lokiclient"
 	"github.com/grafana/grafana-app-sdk/simple"
 )
 
+const (
+	lokiDefaultMaxQueryLength = 721 * time.Hour // 30d1h, matches the default value in Loki
+	lokiDefaultMaxQuerySize   = 65536           // 64kb
+)
+
 type NotificationConfig struct {
 	Enabled bool
 	Loki    lokiclient.LokiConfig
@@ -14,3 +24,49 @@ type RuntimeConfig struct {
 	GetAlertStateHistoryHandler simple.AppCustomRouteHandler
 	Notification                NotificationConfig
 }
+
+func (n *NotificationConfig) AddFlagsWithPrefix(prefix string, flags *pflag.FlagSet) {
+	flags.BoolVar(&n.Enabled, prefix+".enabled", false, "Enable notification query endpoints")
+	addLokiFlags(&n.Loki, prefix+".loki", flags)
+}
+
+func (r *RuntimeConfig) AddFlagsWithPrefix(prefix string, flags *pflag.FlagSet) {
+	r.Notification.AddFlagsWithPrefix(prefix+".notification", flags)
+}
+
+func (r *RuntimeConfig) AddFlags(flags *pflag.FlagSet) {
+	r.AddFlagsWithPrefix("alerting.historian", flags)
+}
+
+type urlVar struct {
+	u **url.URL
+}
+
+// String implements flag.Value
+func (v urlVar) String() string {
+	if v.u == nil || *v.u == nil {
+		return ""
+	}
+	return (*v.u).Redacted()
+}
+
+// Set implements flag.Value
+func (v urlVar) Set(s string) error {
+	u, err := url.Parse(s)
+	if err != nil {
+		return err
+	}
+	*v.u = u
+	return nil
+}
+
+// Type implements flag.Value
+func (v urlVar) Type() string {
+	return "url"
+}
+
+func addLokiFlags(l *lokiclient.LokiConfig, prefix string, flags *pflag.FlagSet) {
+	flags.Var(urlVar{&l.ReadPathURL}, prefix+".read-url", "URL to Loki instance for performing queries")
+	flags.DurationVar(&l.MaxQueryLength, prefix+".max-query-length", lokiDefaultMaxQueryLength, "Maximum allowed time range for queries")
+	flags.IntVar(&l.MaxQuerySize, prefix+".max-query-size", lokiDefaultMaxQuerySize, "Maximum allowed size of a query string passed to Loki")
+}

apps/alerting/historian/pkg/app/config/config_test.go

@@ -0,0 +1,85 @@
+package config
+
+import (
+	"net/url"
+	"testing"
+	"time"
+
+	"github.com/grafana/alerting/notify/historian/lokiclient"
+	"github.com/spf13/pflag"
+	"github.com/stretchr/testify/require"
+)
+
+func TestRuntimeConfig(t *testing.T) {
+	lokiURL := mustParseURL("http://localhost:3100")
+
+	tests := []struct {
+		name     string
+		args     []string
+		expected RuntimeConfig
+	}{
+		{
+			name: "default config",
+			args: []string{},
+			expected: RuntimeConfig{
+				Notification: NotificationConfig{
+					Enabled: false,
+					Loki: lokiclient.LokiConfig{
+						ReadPathURL:    nil,
+						MaxQueryLength: 721 * time.Hour,
+						MaxQuerySize:   65536,
+					},
+				},
+			},
+		},
+		{
+			name: "with notification enabled",
+			args: []string{"--alerting.historian.notification.enabled"},
+			expected: RuntimeConfig{
+				Notification: NotificationConfig{
+					Enabled: true,
+					Loki: lokiclient.LokiConfig{
+						ReadPathURL:    nil,
+						MaxQueryLength: 721 * time.Hour,
+						MaxQuerySize:   65536,
+					},
+				},
+			},
+		},
+		{
+			name: "with loki read url",
+			args: []string{"--alerting.historian.notification.loki.read-url=http://localhost:3100"},
+			expected: RuntimeConfig{
+				Notification: NotificationConfig{
+					Enabled: false,
+					Loki: lokiclient.LokiConfig{
+						ReadPathURL:    lokiURL,
+						MaxQueryLength: 721 * time.Hour,
+						MaxQuerySize:   65536,
+					},
+				},
+			},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			cfg := &RuntimeConfig{}
+			flags := pflag.NewFlagSet("test", pflag.ContinueOnError)
+
+			cfg.AddFlags(flags)
+
+			err := flags.Parse(tt.args)
+			require.NoError(t, err)
+			require.Equal(t, tt.expected, *cfg)
+		})
+	}
+}
+
+func mustParseURL(s string) *url.URL {
+	u, err := url.Parse(s)
+	if err != nil {
+		panic(err)
+	}
+	return u
+}