Add alt_stat_name to cluster (#484)

Signed-off-by: Rama <rama.rao@salesforce.com>

envoy/api/v2/cds.proto

@@ -38,17 +38,22 @@ service ClusterDiscoveryService {
 // [#protodoc-title: Clusters]
 
 // Configuration for a single upstream cluster.
-// [#comment:next free field: 28]
+// [#comment:next free field: 29]
 message Cluster {
   // Supplies the name of the cluster which must be unique across all clusters.
   // The cluster name is used when emitting
-  // :ref:`statistics <config_cluster_manager_cluster_stats>`.
+  // :ref:`statistics <config_cluster_manager_cluster_stats>` if :ref:`alt_stat_name
+  // <envoy_api_field_Cluster.alt_stat_name>` is not provided.
   // Any ``:`` in the cluster name will be converted to ``_`` when emitting statistics.
   // By default, the maximum length of a cluster name is limited to 60
   // characters. This limit can be increased by setting the
   // :option:`--max-obj-name-len` command line argument to the desired value.
   string name = 1 [(validate.rules).string.min_bytes = 1];
 
+  // An optional alternative to the cluster name to be used while emitting stats.
+  // Any ``:`` in the name will be converted to ``_`` when emitting statistics.
+  string alt_stat_name = 28;
+
   // Refer to :ref:`service discovery type <arch_overview_service_discovery_types>`
   // for an explanation on each type.
   enum DiscoveryType {