Validate Redis session store health on startup

pkg/validation/sessions.go

@@ -1,9 +1,13 @@
 package validation
 
 import (
+	"context"
+	"fmt"
 	"time"
 
 	"github.com/oauth2-proxy/oauth2-proxy/pkg/apis/options"
+	"github.com/oauth2-proxy/oauth2-proxy/pkg/encryption"
+	"github.com/oauth2-proxy/oauth2-proxy/pkg/sessions/redis"
 )
 
 func validateSessionCookieMinimal(o *options.Options) []string {
@@ -30,3 +34,50 @@ func validateSessionCookieMinimal(o *options.Options) []string {
 	}
 	return msgs
 }
+
+// validateRedisSessionStore builds a Redis Client from the options and
+// attempts to connect, Set, Get and Del a random health check key
+func validateRedisSessionStore(o *options.Options) []string {
+	if o.Session.Type != options.RedisSessionStoreType {
+		return []string{}
+	}
+
+	client, err := redis.NewRedisClient(o.Session.Redis)
+	if err != nil {
+		return []string{fmt.Sprintf("unable to initialize a redis client: %v", err)}
+	}
+
+	nonce, err := encryption.Nonce()
+	if err != nil {
+		return []string{fmt.Sprintf("unable to generate a redis initialization test key: %v", err)}
+	}
+
+	key := fmt.Sprintf("%s-healthcheck-%s", o.Cookie.Name, nonce)
+	return sendRedisConnectionTest(client, key, nonce)
+}
+
+func sendRedisConnectionTest(client redis.Client, key string, val string) []string {
+	msgs := []string{}
+	ctx := context.Background()
+
+	err := client.Set(ctx, key, []byte(val), time.Duration(60)*time.Second)
+	if err != nil {
+		msgs = append(msgs, fmt.Sprintf("unable to set a redis initialization key: %v", err))
+	} else {
+		gval, err := client.Get(ctx, key)
+		if err != nil {
+			msgs = append(msgs,
+				fmt.Sprintf("unable to retrieve redis initialization key: %v", err))
+		}
+		if string(gval) != val {
+			msgs = append(msgs,
+				"the retrieved redis initialization key did not match the value we set")
+		}
+	}
+
+	err = client.Del(ctx, key)
+	if err != nil {
+		msgs = append(msgs, fmt.Sprintf("unable to delete the redis initialization key: %v", err))
+	}
+	return msgs
+}