Zeroconf offline-handling improvements (#77)

* Add benchmark.py

* Add cpu / disk benchmark APIs

* Add cpu_benchmark method to distributed_job_manager.py

* Do a better job of storing hostnames =

* Remove hostname from Zeroconf cache if server goes offline

* Add cpu / disk benchmark APIs

* Add cpu_benchmark method to distributed_job_manager.py

* Do a better job of storing hostnames =

* Remove hostname from Zeroconf cache if server goes offline

* Wrap main code in try finally block to always stop zeroconf

* Add missing import

src/utilities/zeroconf_server.py

@@ -56,7 +56,7 @@ class ZeroconfServer:
             cls.service_info = info
             cls.zeroconf.register_service(info)
             logger.info(f"Registered zeroconf service: {cls.service_info.name}")
-        except NonUniqueNameException as e:
+        except (NonUniqueNameException, socket.gaierror) as e:
             logger.error(f"Error establishing zeroconf: {e}")
 
     @classmethod
@@ -74,17 +74,17 @@ class ZeroconfServer:
     @classmethod
     def _on_service_discovered(cls, zeroconf, service_type, name, state_change):
         info = zeroconf.get_service_info(service_type, name)
-        logger.debug(f"Zeroconf: {name} {state_change}")
+        hostname = name.split(f'.{cls.service_type}')[0]
+        logger.debug(f"Zeroconf: {hostname} {state_change}")
         if service_type == cls.service_type:
             if state_change == ServiceStateChange.Added or state_change == ServiceStateChange.Updated:
-                cls.client_cache[name] = info
+                cls.client_cache[hostname] = info
             else:
-                cls.client_cache.pop(name)
-            pub.sendMessage('zeroconf_state_change', hostname=name, state_change=state_change, info=info)
+                cls.client_cache.pop(hostname)
+            pub.sendMessage('zeroconf_state_change', hostname=hostname, state_change=state_change)
 
     @classmethod
     def found_hostnames(cls):
-        fetched_hostnames = [x.split(f'.{cls.service_type}')[0] for x in cls.client_cache.keys()]
         local_hostname = socket.gethostname()
 
         def sort_key(hostname):
@@ -92,13 +92,12 @@ class ZeroconfServer:
             return False if hostname == local_hostname else True
 
         # Sort the list with the local hostname first
-        sorted_hostnames = sorted(fetched_hostnames, key=sort_key)
+        sorted_hostnames = sorted(cls.client_cache.keys(), key=sort_key)
         return sorted_hostnames
 
     @classmethod
     def get_hostname_properties(cls, hostname):
-        new_key = hostname + '.' + cls.service_type
-        server_info = cls.client_cache.get(new_key).properties
+        server_info = cls.client_cache.get(hostname).properties
         decoded_server_info = {key.decode('utf-8'): value.decode('utf-8') for key, value in server_info.items()}
         return decoded_server_info