Add new property for GatewayTagsProvider

Avoid conflict with the ability to add custom tags.  Fixes #4007

Author: ryanjbaxter

docs/modules/ROOT/pages/spring-cloud-gateway/global-filters.adoc

@@ -52,10 +52,12 @@ This filter adds a timer metric named `spring.cloud.gateway.requests` with the f
 * `httpStatusCode`: The HTTP Status of the request returned to the client.
 * `httpMethod`: The HTTP method used for the request.
 
-In addition, through the `spring.cloud.gateway.metrics.tags.path.enabled` property (by default, `false`), you can activate an extra metric with the path tag:
+In addition, through the `spring.cloud.gateway.metrics.path-tags.enabled` property (by default, `false`), you can activate an extra metric with the path tag:
 
 * `path`: The path of the request.
 
+WARNING: The property `spring.cloud.gateway.metrics.tags.path.enabled` will also add the above metric but has the side effect of the value ending up as a tag.  This property is deprecated and will be removed in a future release.
+
 These metrics are then available to be scraped from `/actuator/metrics/spring.cloud.gateway.requests` and can be easily integrated with Prometheus to create a link:images/gateway-grafana-dashboard.jpeg[Grafana] link:gateway-grafana-dashboard.json[dashboard].
 You can also alarm with these useful metrics to take an example from link:gateway-alarming.adoc[alarming-template].
 

spring-cloud-gateway-server/src/main/java/org/springframework/cloud/gateway/config/GatewayMetricsAutoConfiguration.java

@@ -32,6 +32,7 @@
 import org.springframework.boot.autoconfigure.AutoConfigureBefore;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnClass;
+import org.springframework.boot.autoconfigure.condition.ConditionalOnExpression;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnMissingBean;
 import org.springframework.boot.autoconfigure.condition.ConditionalOnProperty;
 import org.springframework.boot.autoconfigure.web.reactive.HttpHandlerAutoConfiguration;
@@ -69,8 +70,10 @@ public GatewayHttpTagsProvider gatewayHttpTagsProvider() {
 		return new GatewayHttpTagsProvider();
 	}
 
+	// TODO: remove support for the property `metrics.tags.path.enabled` in the next major
 	@Bean
-	@ConditionalOnProperty(name = GatewayProperties.PREFIX + ".metrics.tags.path.enabled")
+	@ConditionalOnExpression("'${" + GatewayProperties.PREFIX + ".metrics.tags.path.enabled:false}' == 'true' || '${"
+			+ GatewayProperties.PREFIX + ".metrics.path-tags-provider.enabled:false}' == 'true'")
 	public GatewayPathTagsProvider gatewayPathTagsProvider() {
 		return new GatewayPathTagsProvider();
 	}

spring-cloud-gateway-server/src/main/resources/META-INF/additional-spring-configuration-metadata.json

@@ -436,6 +436,22 @@
       "type": "java.lang.Boolean",
       "description": "If RedisRouteDefinitionRepository should be enabled.",
       "defaultValue": "true"
+    },
+    {
+      "name": "spring.cloud.gateway.metrics.tags.path.enabled",
+      "type": "java.lang.Boolean",
+      "description": "Enables the gateway path tag provider.",
+      "defaultValue": "false",
+      "deprecation": {
+        "reason": "Setting this property to true will cause the path tag to be added to all metrics.",
+        "replacement": "spring.cloud.gateway.metrics.path-tags-provider.enabled"
+      }
+    },
+    {
+      "name": "spring.cloud.gateway.metrics.path-tags-provider.enabled",
+      "type": "java.lang.Boolean",
+      "description": "Enables the gateway path tag provider.",
+      "defaultValue": "false"
     }
   ]
 }