How can I create reliable flask-SQLAlchemy interactions with server-side-events? - flask-sqlalchemy

Question

I have a flask app that is functioning to expectations, and I am now trying to add a message notification section to my page. The difficulty I am having is that the database changes I am trying to rely upon do not seem to be updating in a timely fashion.
The html code is elementary:
<ul id="out" cols="85" rows="14">
</ul><br><br>
<script type="text/javascript">
var ul = document.getElementById("out");
var eventSource = new EventSource("/stream_game_channel");
eventSource.onmessage = function(e) {
ul.innerHTML += e.data + '<br>';
}
</script>
Here is the msg write code that the second user is executing. I know the code block is run because the redis trigger is properly invoked:
msg_join = Messages(game_id=game_id[0],
type="gameStart",
msg_from=current_user.username,
msg_to="Everyone",
message=f'{current_user.username} has requested to join.')
db.session.add(msg_join)
db.session.commit()
channel = str(game_id[0]).zfill(5) + 'startGame'
session['channel'] = channel
date_time = datetime.utcnow().strftime("%Y/%m/%d %H:%M:%S")
redisChannel.set(channel, date_time)
Here is the flask stream code, which is correctly triggered by a new redis time, but when I pull the list of messages, the new message the the second user has added is not yet accessible:
#games.route('/stream_game_channel')
def stream_game_channel():
#stream_with_context
def eventStream():
channel = session.get('channel')
game_id = int(left(channel, 5))
cnt = 0
while cnt < 1000:
print(f'cnt = 0 process running from: {current_user.username}')
time.sleep(1)
ntime = redisChannel.get(channel)
if cnt == 0:
msgs = db.session.query(Messages).filter(Messages.game_id == game_id)
msg_list = [i.message for i in msgs]
cnt += 1
ltime = ntime
lmsg_list = msg_list
for i in msg_list:
yield "data: {}\n\n".format(i)
elif ntime != ltime:
print(f'cnt > 0 process running from: {current_user.username}')
time.sleep(3)
msgs = db.session.query(Messages).filter(Messages.game_id == game_id)
msg_list = [i.message for i in msgs]
new_messages = # need to write this code still
ltime = ntime
cnt += 1
yield "data: {}\n\n".format(msg_list[len(msg_list)-len(lmsg_list)])
return Response(eventStream(), mimetype="text/event-stream")
The syntactic error that I am running into is that the msg_list is exactly the same length (i.e the pushed new message does not get written when i expect it to). Strangely, the second user's session appears to be accessing this information because its stream correctly reflects the addition.
I am using an Amazon RDS MySQL database.

Answer 1

The solution was to utilize a db.session.commit() before my db.session.query(Messages).filter(...) even where no writes were pending. This enabled an immediate read from a different user session, and my code commenced to react to the change in message list length properly.