[nexus] Add a new user for service balancing

nexus/src/app/mod.rs

@@ -223,6 +223,16 @@ impl Nexus {
         &self.opctx_external_authn
     }
 
+    /// Returns an [`OpContext`] used for balancing services.
+    pub fn opctx_for_service_balancer(&self) -> OpContext {
+        OpContext::for_background(
+            self.log.new(o!("component" => "ServiceBalancer")),
+            Arc::clone(&self.authz),
+            authn::Context::internal_service_balancer(),
+            Arc::clone(&self.db_datastore),
+        )
+    }
+
     /// Used as the body of a "stub" endpoint -- one that's currently
     /// unimplemented but that we eventually intend to implement
     ///

nexus/src/authn/mod.rs

@@ -35,6 +35,7 @@ pub use crate::db::fixed_data::user_builtin::USER_EXTERNAL_AUTHN;
 pub use crate::db::fixed_data::user_builtin::USER_INTERNAL_API;
 pub use crate::db::fixed_data::user_builtin::USER_INTERNAL_READ;
 pub use crate::db::fixed_data::user_builtin::USER_SAGA_RECOVERY;
+pub use crate::db::fixed_data::user_builtin::USER_SERVICE_BALANCER;
 use crate::db::model::ConsoleSession;
 
 use crate::authz;
@@ -170,6 +171,11 @@ impl Context {
         Context::context_for_builtin_user(USER_DB_INIT.id)
     }
 
+    /// Returns an authenticated context for Nexus-driven service balancing.
+    pub fn internal_service_balancer() -> Context {
+        Context::context_for_builtin_user(USER_SERVICE_BALANCER.id)
+    }
+
     fn context_for_builtin_user(user_builtin_id: Uuid) -> Context {
         Context {
             kind: Kind::Authenticated(Details {
@@ -217,6 +223,7 @@ mod test {
     use super::USER_INTERNAL_API;
     use super::USER_INTERNAL_READ;
     use super::USER_SAGA_RECOVERY;
+    use super::USER_SERVICE_BALANCER;
     use super::USER_TEST_PRIVILEGED;
     use super::USER_TEST_UNPRIVILEGED;
     use crate::db::fixed_data::user_builtin::USER_EXTERNAL_AUTHN;
@@ -251,6 +258,10 @@ mod test {
         let actor = authn.actor().unwrap();
         assert_eq!(actor.actor_id(), USER_DB_INIT.id);
 
+        let authn = Context::internal_service_balancer();
+        let actor = authn.actor().unwrap();
+        assert_eq!(actor.actor_id(), USER_SERVICE_BALANCER.id);
+
         let authn = Context::internal_saga_recovery();
         let actor = authn.actor().unwrap();
         assert_eq!(actor.actor_id(), USER_SAGA_RECOVERY.id);

nexus/src/db/datastore.rs

@@ -3250,6 +3250,7 @@ impl DataStore {
         let builtin_users = [
             // Note: "db_init" is also a builtin user, but that one by necessity
             // is created with the database.
+            &*authn::USER_SERVICE_BALANCER,
             &*authn::USER_INTERNAL_API,
             &*authn::USER_INTERNAL_READ,
             &*authn::USER_EXTERNAL_AUTHN,

nexus/src/db/fixed_data/role_assignment.rs

@@ -24,6 +24,13 @@ lazy_static! {
                 *FLEET_ID,
                 role_builtin::FLEET_ADMIN.role_name,
             ),
+            RoleAssignment::new(
+                IdentityType::UserBuiltin,
+                user_builtin::USER_SERVICE_BALANCER.id,
+                role_builtin::FLEET_ADMIN.resource_type,
+                *FLEET_ID,
+                role_builtin::FLEET_ADMIN.role_name,
+            ),
 
             // The "internal-read" user gets the "viewer" role on the sole
             // Fleet.  This will grant them the ability to read various control

nexus/src/db/fixed_data/user_builtin.rs

@@ -39,6 +39,15 @@ lazy_static! {
             "used for seeding initial database data",
         );
 
+    /// Internal user for performing operations to manage the
+    /// provisioning of services across the fleet.
+    pub static ref USER_SERVICE_BALANCER: UserBuiltinConfig =
+        UserBuiltinConfig::new_static(
+            "001de000-05e4-4000-8000-00000000bac3",
+            "service-balancer",
+            "used for Nexus-driven service balancing",
+        );
+
     /// Internal user used by Nexus when handling internal API requests
     pub static ref USER_INTERNAL_API: UserBuiltinConfig =
         UserBuiltinConfig::new_static(
@@ -82,9 +91,11 @@ mod test {
     use super::USER_INTERNAL_API;
     use super::USER_INTERNAL_READ;
     use super::USER_SAGA_RECOVERY;
+    use super::USER_SERVICE_BALANCER;
 
     #[test]
     fn test_builtin_user_ids_are_valid() {
+        assert_valid_uuid(&USER_SERVICE_BALANCER.id);
         assert_valid_uuid(&USER_DB_INIT.id);
         assert_valid_uuid(&USER_INTERNAL_API.id);
         assert_valid_uuid(&USER_EXTERNAL_AUTHN.id);

nexus/tests/integration_tests/users_builtin.rs

@@ -27,6 +27,9 @@ async fn test_users_builtin(cptestctx: &ControlPlaneTestContext) {
 
     let u = users.remove(&authn::USER_DB_INIT.name.to_string()).unwrap();
     assert_eq!(u.identity.id, authn::USER_DB_INIT.id);
+    let u =
+        users.remove(&authn::USER_SERVICE_BALANCER.name.to_string()).unwrap();
+    assert_eq!(u.identity.id, authn::USER_SERVICE_BALANCER.id);
     let u = users.remove(&authn::USER_INTERNAL_API.name.to_string()).unwrap();
     assert_eq!(u.identity.id, authn::USER_INTERNAL_API.id);
     let u = users.remove(&authn::USER_INTERNAL_READ.name.to_string()).unwrap();