[config][generic-update] Implement ChangeApplier for ConfigDb format

generic_config_updater/change_applier.py

@@ -0,0 +1,98 @@
+import json
+from jsonpatch import PatchOperation, AddOperation, RemoveOperation, ReplaceOperation
+from swsscommon.swsscommon import ConfigDBConnector
+from .gu_common import GenericConfigUpdaterError, JsonChange
+
+class ChangeApplier:
+    def __init__(self, service_metadata_file: str=None):
+        self.config_db = ConfigDBConnector()
+        self.config_db.connect()
+        service_metadata = {}
+        if service_metadata_file:
+            with open(service_metadata_file, 'r') as f:
+                service_metadata = json.load(f)
+        self.table_service = service_metadata.get('tables', {})
+        self.service_commands = service_metadata.get('services', {})
+        self.valiate_metadata()
+        self.previous_table_name = None
+
+    def valiate_metadata(self):
+        # TODO: check metadata file syntax
+        pass
+
+    def exec_command(self, cmd) -> int:
+        p = subprocess.Popen(cmd)
+        p.communicate()
+        return p.returncode
+
+    def on_table_operation(self, table_name):
+        services = self.table_service.get(table_name, {})
+        for service in services:
+            commands = self.service_commands.get(service, {})
+            restart_comand = commands.get('restart-command')
+            if restart_comand:
+                rc = self.exec_command(restart_comand)
+                if rc != 0:
+                    raise GenericConfigUpdaterError(f"Restart command failed: {restart_comand}, rc={rc}")
+            validate_command = commands.get('validate-commands')
+            if validate_command:
+                rc = self.exec_command(validate_command)
+                if rc != 0:
+                    raise GenericConfigUpdaterError(f"Validate command failed: {validate_command}, rc={rc}")
+
+    def on_table_operation_lazy(self, table_name):
+        # Optimze: reduce the duplicated restarting in a batch
+        if table_name != self.previous_table_name:
+            self.on_table_operation(self.previous_table_name)
+            self.previous_table_name = table_name
+
+    def _apply_entry(self, op: PatchOperation):
+        parts = op.pointer.parts
+        entry = self.config_db.get_entry(parts[0], parts[1])
+        oldtree = entry
+        for part in parts[1::-1]:
+            oldtree = { part: oldtree }
+        op.apply(oldtree)
+        self.config_db.set_entry(parts[0], parts[1], entry)
+
+    def apply(self, change: JsonChange):
+        ## Note: ordering of applying the modifications in a JsonChange is arbitrary
+
+        ## TODO: The implementation is not optimized.
+        ## Please folllow the stages in design doc https://github.com/Azure/SONiC/blob/master/doc/config-generic-update-rollback/Json_Change_Application_Design.md#22-functional-description
+        patch = change.patch
+
+        self.previous_table_name = None
+        # JsonChange is a list of PatchOperation
+        for op in patch._ops:
+            parts = op.pointer.parts
+            nparts = len(parts)
+            value = op.operation.get('value', None)
+
+
+            tree = value
+            for part in parts[::-1]:
+                tree = { part: tree }
+            if isinstance(op, AddOperation):
+                self.config_db.mod_config(tree)
+                if nparts == 2:
+                    # Added a key in a table
+                    self.on_table_operation_lazy(parts[0])
+            elif isinstance(op, RemoveOperation):
+                if nparts == 1:
+                    # Delete a table
+                    self.config_db.delete_table(parts[0])
+                    self.on_table_operation_lazy(parts[0])
+                elif nparts == 2:
+                    # Delete a key in a table
+                    self.config_db.set_entry(parts[0], parts[1], None)
+                    self.on_table_operation_lazy(parts[0])
+                else:
+                    self._apply_entry(op)
+            elif isinstance(op, ReplaceOperation):
+                if nparts <= 2:
+                    raise NotImplementedError("ConfigDb does not support replace a table name or key name")
+                else:
+                    self._apply_entry(op)
+            else:
+                raise NotImplementedError("Not supported PatchOperation type")

generic_config_updater/generic_updater.py

@@ -4,6 +4,7 @@
 from .gu_common import GenericConfigUpdaterError, ConfigWrapper, \
                        DryRunConfigWrapper, PatchWrapper
 from .patch_sorter import PatchSorter
+from .change_applier import ChangeApplier
 
 CHECKPOINTS_DIR = "/etc/sonic/checkpoints"
 CHECKPOINT_EXT = ".cp.json"
@@ -17,11 +18,6 @@ def release_lock(self):
         # TODO: Implement ConfigLock
         pass
 
-class ChangeApplier:
-    def apply(self, change):
-        # TODO: Implement change applier
-        raise NotImplementedError("ChangeApplier.apply(change) is not implemented yet")
-
 class ConfigFormat(Enum):
     CONFIGDB = 1
     SONICYANG = 2