diff --git a/src/ray/protobuf/autoscaler.proto b/src/ray/protobuf/autoscaler.proto
index 4373c137d209..d111d113c621 100644
--- a/src/ray/protobuf/autoscaler.proto
+++ b/src/ray/protobuf/autoscaler.proto
@@ -51,12 +51,46 @@ message PlacementConstraint {
   optional AffinityConstraint affinity = 2;
 }
 
+// The type of operator to use for the label constraint.
+enum LabelOperator {
+  LABEL_OPERATOR_UNSPECIFIED = 0;
+  // This is to support equality or in semantics.
+  LABEL_OPERATOR_IN = 1;
+  // This is to support not equal or not in semantics.
+  LABEL_OPERATOR_NOT_IN = 2;
+}
+
+// A node label constraint with a key, one or a list of values and an operator.
+message LabelConstraint {
+  // The key of the label
+  string label_key = 1;
+  // The operator to use for the label constraint.
+  LabelOperator operator = 2;
+  // The values to check against.
+  repeated string label_values = 3;
+}
+
+// A list of node label constraints to specify the label requirements in a
+// resource request.
+message LabelSelector {
+  // The list of node label constraints with AND semantics.
+  repeated LabelConstraint label_constraints = 1;
+}
+
 message ResourceRequest {
   // resource requirements for the request.
   map<string, double> resources_bundle = 1;
   // placement constraint for the request. multiple constraints
   // form AND semantics.
   repeated PlacementConstraint placement_constraints = 2;
+  // The node label requirements for the request. Multiple label selectors are for
+  // fallback mechanism. When trying to find a node that satisfies the label
+  // requirements, the first label selector should be tried first, if not found,
+  // the second label selector should be tried, and so on.
+  // Note that When the ResourceRequest is used within a BundleSelector for
+  // GangResourceRequest, the fallback mechanism is done at the BundleSelector level.
+  // So in that case, the label_selectors will only contain a single LabelSelector.
+  repeated LabelSelector label_selectors = 3;
 }
 
 message ResourceRequestByCount {
@@ -64,14 +98,27 @@ message ResourceRequestByCount {
   int64 count = 2;
 }
 
-// All bundles in the same resource request require gang
+// A bundle selector used to specify the resource bundles that should be
+// allocated together. All bundles in the same resource request require gang
 // allocation semantics: they should be allocated all or nothing.
+message BundleSelector {
+  // The list of resource requests that should be allocated together.
+  repeated ResourceRequest resource_requests = 1;
+}
+
 message GangResourceRequest {
   // a map from bundles to the number of bundles requested.
+  // DEPRECATED: bundle_selector should be used instead so that we can support fallback
+  // mechanism.
   repeated ResourceRequest requests = 1;
   // Metadata associated with the request for observability,
   // e.g. placement group's strategy.
   string details = 2;
+  // The bundle requests. Multiple bundle selectors are for fallback mechanism.
+  // When trying to find nodes that satisfies the bundle selector, the first bundle
+  // selector should be tried first, if not found, the second bundle selector should be
+  // tried, and so on.
+  repeated BundleSelector bundle_selectors = 3;
 }
 
 // Cluster resource constraint represents minimal cluster size requirement,