Flask-Superset Error "Failed to serialize session data: Encoding objects of type LazyString is unsupported" with Redis Session Backend

[weigosw]

Question:

I am encountering an issue when configuring Flask-Superset to use Redis as the session backend. Every time I attempt to import a file, the file uploads successfully, then I get the following error:

Failed to serialize session data: Encoding objects of type LazyString is unsupported

Environment:

• Flask: 1.1.x
• Superset: Version 4.0.1
• Redis: Running in a Docker container
• Flask-Babel: Used for multilingual support

Configuration:

Here is the content of my superset_config.py file:

import os
from redis import Redis


# Secret key
SECRET_KEY = 'GoOeN5Uo3wEPliy3PgAgpCi36vw9GEjN9N6ZZR3pEDSH/6E8nkf1ha4d'

# PostgreSQL database URI
SQLALCHEMY_DATABASE_URI = 'postgresql://superset:superset2024@localhost/superset'

LANGUAGES = {
    'zh': {'flag': 'cn', 'name': 'Chinese'},
    'en': {'flag': 'us', 'name': 'English'},
}

# Setup default language
BABEL_DEFAULT_LOCALE = 'zh'

print("Config Used!")


# Session configuration
SESSION_TYPE = "redis"
SESSION_REDIS = Redis(host="localhost", port=6379, db=0)
SESSION_SERVER_SIDE = True

Error Log:

Every time I attempt to import a file, the file is uploaded, but the following error appears in the log:

2024-06-24 21:45:08,864:DEBUG:superset.stats_logger:[stats_logger] (incr) failed_excel_upload
2024-06-24 21:45:08,865:ERROR:superset.app:Failed to serialize session data: Encoding objects of type LazyString is unsupported
2024-06-24 21:45:08,865:ERROR:superset.app:Exception on /exceltodatabaseview/form [POST]
Traceback (most recent call last):
  File "/Users/suwei/.pyenv/versions/3.9.19/envs/superset-env/lib/python3.9/site-packages/flask/app.py", line 2190, in wsgi_app
    response = self.full_dispatch_request()
  File "/Users/suwei/.pyenv/versions/3.9.19/envs/superset-env/lib/python3.9/site-packages/flask/app.py", line 1487, in full_dispatch_request
    return self.finalize_request(rv)
  File "/Users/suwei/.pyenv/versions/3.9.19/envs/superset-env/lib/python3.9/site-packages/flask/app.py", line 1508, in finalize_request
    response = self.process_response(response)
  File "/Users/suwei/.pyenv/versions/3.9.19/envs/superset-env/lib/python3.9/site-packages/flask/app.py", line 2005, in process_response
    self.session_interface.save_session(self, ctx.session, response)
  File "/Users/suwei/.pyenv/versions/3.9.19/envs/superset-env/lib/python3.9/site-packages/flask_session/base.py", line 305, in save_session
    self._upsert_session(app.permanent_session_lifetime, session, store_id)
  File "/Users/suwei/.pyenv/versions/3.9.19/envs/superset-env/lib/python3.9/site-packages/flask_session/redis/redis.py", line 78, in _upsert_session
    serialized_session_data = self.serializer.encode(session)
  File "/Users/suwei/.pyenv/versions/3.9.19/envs/superset-env/lib/python3.9/site-packages/flask_session/base.py", line 132, in encode
    return self.encoder.encode(dict(session))
TypeError: Encoding objects of type LazyString is unsupported

Attempted Solutions:

1. Custom JSONEncoder class to handle LazyString objects by converting them to strings.
2. Created custom session class and session interface and applied these custom classes in superset_config.py.

import os
import json
from redis import Redis
from flask.sessions import SessionInterface, SessionMixin
from flask_babel import LazyString
from flask_session import Session
from werkzeug.datastructures import CallbackDict
from datetime import timedelta

# Secret key
SECRET_KEY = 'GoOeN5Uo3wEPliy3PgAgpCi36vw9GEjN9N6ZZR3pEDSH/6E8nkf1ha4d'

# PostgreSQL database URI
SQLALCHEMY_DATABASE_URI = 'postgresql://superset:superset2024@localhost/superset'

LANGUAGES = {
    'zh': {'flag': 'cn', 'name': 'Chinese'},
    'en': {'flag': 'us', 'name': 'English'},
}

# Setup default language
BABEL_DEFAULT_LOCALE = 'zh'

print("Config Used!")

# Custom JSONEncoder to handle LazyString
class CustomJSONEncoder(json.JSONEncoder):
    def default(self, obj):
        if isinstance(obj, LazyString):
            return str(obj)
        return super().default(obj)

# Custom session class
class CustomSession(CallbackDict, SessionMixin):
    def __init__(self, initial=None, permanent=True):
        def on_update(self):
            self.modified = True
        CallbackDict.__init__(self, initial, on_update)
        self.permanent = permanent
        self.modified = False
        self.new = True

class CustomSessionInterface(SessionInterface):
    serializer = CustomJSONEncoder()
    session_class = CustomSession

    def open_session(self, app, request):
        s = request.cookies.get(app.session_cookie_name)
        if not s:
            return self.session_class()
        data = self.serializer.decode(s)
        return self.session_class(data)

    def save_session(self, app, session, response):
        domain = self.get_cookie_domain(app)
        if not session:
            if session.modified:
                response.delete_cookie(app.session_cookie_name, domain=domain)
            return
        expires = self.get_expiration_time(app, session)
        val = self.serializer.encode(dict(session))
        response.set_cookie(app.session_cookie_name, val, expires=expires, httponly=True, domain=domain)

# Session configuration
SESSION_TYPE = "redis"
SESSION_REDIS = Redis(host="localhost", port=6379, db=0)
SESSION_USE_SIGNER = True
SESSION_PERMANENT = True
SESSION_SERVER_SIDE = True
SESSION_FILE_THRESHOLD = 100
SESSION_KEY_PREFIX = "session:"
SESSION_LIFETIME = timedelta(days=31)

# Initialize session
SESSION = Session()

def print_superset_config():
    from flask import current_app

    config_items = {key: value for key, value in current_app.config.items() if key.isupper()}
    for key, value in config_items.items():
        print(f"{key}: {value}")

Request for Help:

How can I correctly configure Superset to use Redis as the session backend and resolve the issue with LazyString objects not being serializable? Are there any other methods to ensure LazyString objects are properly handled?

Any help or suggestions would be greatly appreciated!