Check if backup name exists and add retry on ClickhouseError for quer…

…ies (#173)

* Check if backup with given name already exists

* Add retry for query on ClickhouseError

ch_backup/ch_backup.py

@@ -106,6 +106,14 @@ def backup(
         """
         # pylint: disable=too-many-branches
         # pylint: disable=too-many-locals
+        backups_with_light_meta = self._context.backup_layout.get_backups(
+            use_light_meta=True
+        )
+
+        for backup in backups_with_light_meta:
+            if name == backup.name:
+                raise ClickhouseBackupError(f"Backup with name {name} already exists")
+
         logging.info(f"Backup sources: {sources}")
         assert not (db_names and tables)
 
@@ -127,10 +135,6 @@ def backup(
         if db_names is not None:
             databases = [db for db in databases if db.name in db_names]
 
-        backups_with_light_meta = self._context.backup_layout.get_backups(
-            use_light_meta=True
-        )
-
         last_backup = next(iter(backups_with_light_meta), None)
         if last_backup and not self._check_min_interval(last_backup, force):
             msg = "Backup is skipped per backup.min_interval config option."

ch_backup/clickhouse/client.py

@@ -37,7 +37,7 @@ def settings(self):
         """
         return self._session.params
 
-    @retry(requests.exceptions.ConnectionError)
+    @retry((requests.exceptions.ConnectionError, ClickhouseError))
     def query(
         self,
         query: str,