database: refactor initial check for empty keys

Rather than reading out the entire database, attempt to pop off
empty keys in each database.  This should should speed up
init on platforms with slow disk I/O and prevents reading
large namespaces in memory.

Signed-off-by:  Eric Callahan <arksine.code@gmail.com>

moonraker/components/database.py

@@ -88,16 +88,40 @@ class MoonrakerDatabase:
                     self.namespaces[key.decode()] = self.lmdb_env.open_db(
                         key, txn)
                     remaining = cursor.next()
-                cursor.close()
-                if "moonraker" not in self.namespaces:
-                    mrdb = self.lmdb_env.open_db(b"moonraker", txn)
-                    self.namespaces["moonraker"] = mrdb
-                    txn.put(b'database_version',
-                            self._encode_value(DATABASE_VERSION),
-                            db=mrdb)
-        # Read out all namespaces to remove any invalid keys on init
-        for ns in self.namespaces.keys():
-            self._get_namespace(ns)
+            if "moonraker" not in self.namespaces:
+                mrdb = self.lmdb_env.open_db(b"moonraker", txn)
+                self.namespaces["moonraker"] = mrdb
+                txn.put(b'database_version',
+                        self._encode_value(DATABASE_VERSION),
+                        db=mrdb)
+            # Iterate through all records, checking for invalid keys
+            for ns, db in self.namespaces.items():
+                with txn.cursor(db=db) as cursor:
+                    remaining = cursor.first()
+                    while remaining:
+                        key_buf = cursor.key()
+                        try:
+                            decoded_key = bytes(key_buf).decode()
+                        except Exception:
+                            logging.info("Database Key Decode Error")
+                            decoded_key = ''
+                        if not decoded_key:
+                            hex_key = bytes(key_buf).hex()
+                            try:
+                                invalid_val = self._decode_value(cursor.value())
+                            except Exception:
+                                invalid_val = ""
+                            logging.info(
+                                f"Invalid Key '{hex_key}' found in namespace "
+                                f"'{ns}', dropping value: {repr(invalid_val)}")
+                            try:
+                                remaining = cursor.delete()
+                            except Exception:
+                                logging.exception("Error Deleting LMDB Key")
+                            else:
+                                continue
+                        remaining = cursor.next()
+
         # Protected Namespaces have read-only API access.  Write access can
         # be granted by enabling the debug option.  Forbidden namespaces
         # have no API access.  This cannot be overridden.