pymongo 4: Specify UuidRepresentation=PYTHON_LEGACY

Existing databases will have the old pymongo 3.x format, so we need
to use PYTHON_LEGACY until there is some kind of migration mechanism.
STANDARD would be better (more compatible with Java, C#, etc), but
we only use python any way, so that should not be a significant issue.
Plus, we use orjson encoded fields, so the database is already only
accessible via st2 python code.

st2common/st2common/models/db/__init__.py

@@ -56,6 +56,7 @@
 import ssl as ssl_lib
 
 import six
+from bson.binary import UuidRepresentation
 from oslo_config import cfg
 import mongoengine
 from mongoengine.queryset import visitor
@@ -190,7 +191,16 @@ def _db_connect(
  # 30 seconds, which means it will block up to 30 seconds and fail if there are any SSL related
  # or other errors
  connection_timeout = cfg.CONF.database.connection_timeout
+
+ # TODO: Add uuid_representation option in st2.conf + a migration guide/script.
+ # This preserves the uuid handling from pymongo 3.x, but it is not portable:
+ # https://pymongo.readthedocs.io/en/stable/examples/uuid.html#handling-uuid-data-example
+ uuid_representation = UuidRepresentation.PYTHON_LEGACY
+
  connection = mongoengine.connection.connect(
+ # kwargs are defined by mongoengine and pymongo.MongoClient:
+ # https://docs.mongoengine.org/apireference.html#mongoengine.connect
+ # https://pymongo.readthedocs.io/en/stable/api/pymongo/mongo_client.html#pymongo.mongo_client.MongoClient
  db_name,
  host=db_host,
  port=db_port,
@@ -199,6 +209,7 @@ def _db_connect(
  password=password,
  connectTimeoutMS=connection_timeout,
  serverSelectionTimeoutMS=connection_timeout,
+ uuidRepresentation=uuid_representation,
  **ssl_kwargs,
  **compressor_kwargs,
  )

st2common/st2common/models/db/stormbase.py

@@ -20,6 +20,7 @@
 import bson
 import six
 import mongoengine as me
+from mongoengine.pymongo_support import LEGACY_JSON_OPTIONS
 from oslo_config import cfg
 
 from st2common.util import mongoescape
@@ -105,7 +106,8 @@ def to_serializable_dict(self, mask_secrets=False):
  if isinstance(v, JSON_UNFRIENDLY_TYPES):
  v = str(v)
  elif isinstance(v, me.EmbeddedDocument):
- v = json_decode(v.to_json())
+ # TODO: Allow overriding json_options.uuid_representation via cfg
+ v = json_decode(v.to_json(json_options=LEGACY_JSON_OPTIONS))
 
  serializable_dict[k] = v