Add worker tagging (#862)

This allows workers to have tags assigned to them, which can then be filtered to control which targets they are allowed to serve.

internal/proto/local/controller/servers/services/v1/server_coordination_service.proto

@@ -65,6 +65,12 @@ message StatusRequest {
 
   // Jobs which this worker wants to report the status.
   repeated JobStatus jobs = 20;
+
+  // Whether to update tags from the Server block on this RPC. We only need to
+  // do this at startup or (at some point) SIGHUP, so specifying when it's
+  // changed allows us to avoid constant database operations for something that
+  // won't change very often, if ever.
+  bool update_tags = 30;
 }
 
 enum CHANGETYPE {

internal/proto/local/controller/servers/services/v1/session_service.proto

@@ -33,6 +33,9 @@ service SessionService {
 message LookupSessionRequest {
 	// The session ID from the client
 	string session_id = 10;
+	// The name of the requesting worker, used for filtering to ensure this
+	// worker is allowed to handle this session.
+	string server_id = 20;
 }
 
 // LookupSessionResponse contains information necessary for a client to

internal/proto/local/controller/servers/v1/servers.proto

@@ -13,8 +13,11 @@ message Server {
   // Type of the resource (controller, worker)
   string type = 20;
 
-  // Name of the resource
-  string name = 30;
+  // Name of the resource. This is deprecated because we ended up setting the
+  // private ID and name to be identical, and there is currently no reason we
+  // can think of to allow a given server's name to match another within the
+  // same cluster. So we simply use the private ID and deprecate this.
+  string name = 30 [deprecated = true];
 
   // Description of the resource
   string description = 40;
@@ -27,4 +30,13 @@ message Server {
 
   // Last time there was an update
   storage.timestamp.v1.Timestamp update_time = 70;
+
+  // Tags for workers
+  map<string, TagValues> tags = 80;
 }
+
+// TagValues is used because map fields cannot be repeated but can be a
+// message
+message TagValues {
+  repeated string values = 10;
+}