[#102] Updates for failover

Signed-off-by: Andrey Berezin <a.berezin@yadro.com>

src/frostfs_testlib/storage/cluster.py

@@ -208,6 +208,42 @@ class Cluster:
     def morph_chain(self) -> list[MorphChain]:
         return self.services(MorphChain)
 
+    def nodes(self, services: list[ServiceClass]) -> list[ClusterNode]:
+        """
+        Resolve which cluster nodes hosting the specified services.
+
+        Args:
+            services: list of services to resolve hosting cluster nodes.
+
+        Returns:
+            list of cluster nodes which host specified services.
+        """
+
+        cluster_nodes = set()
+        for service in services:
+            cluster_nodes.update(
+                [node for node in self.cluster_nodes if node.service(type(service)) == service]
+            )
+
+        return list(cluster_nodes)
+
+    def node(self, service: ServiceClass) -> ClusterNode:
+        """
+        Resolve single cluster node hosting the specified service.
+
+        Args:
+            services: list of services to resolve hosting cluster nodes.
+
+        Returns:
+            list of cluster nodes which host specified services.
+        """
+
+        nodes = [node for node in self.cluster_nodes if node.service(type(service)) == service]
+        if not len(nodes):
+            raise RuntimeError(f"Cannot find service {service} on any node")
+
+        return nodes[0]
+
     def services(self, service_type: type[ServiceClass]) -> list[ServiceClass]:
         """
         Get all services in a cluster of specified type.