Django sessionid not created for Locust client - django

Question

I'm running Django 2.2.24 and Locust 2.1.0 for load testing. When I run some Locust test logging in as a the Django admin user, there are no issues - all my GETs work as expected.
Now I am actually logging in as a specific user. From a web interface, Django passes a CSRFtoken and a sessionid token with no problem. From the Locust client however, the sessionid does not show up at all. Not only that, but when I look in the django_session table (where the web tokens do exist), there are no tokens for the Locust client.
I think this is more related to Django session management than to locust - hence the post in this forum.
My locust file looks like this:
def on_start(self):
'''
The start script for each user - this order is important
'''
# Below 3 lines work fine - we get the csrftoken and put it in the header successfully
response = self.client.get("/accounts/login")
self.csrftoken = response.cookies['csrftoken']
self.headers = {'X-CSRFToken': self.csrftoken}
# Now login with username and password as POST
r1 = self.login()
return r1
def login(self):
# admin login and retrieving it's access token
udata = {'username': self.username, 'password': self.password}
cookies=self.client.cookies.get_dict())
#csrftoken cookie does exist, sessionid does not yet.
log.info("Current cookies in Login:" + str(self.client.cookies))
# This next line should come back with a sessionid
# from Django - but it does not.
response = self.client.post("/accounts/login/",
data=json.dumps(udata),
headers=self.headers)
log.info("Response from client.post="+str(response)) #OK
log.info("Response status code:" + str(response.status_code))
log.info("Response text=" + response.text)
# Next line does not contain sessionid or Set-Cookie
log.info("Headers from post/accts/login = " + str(response.headers))
Thanks for any assistance.

Answer 1

Change
response = self.client.post("/accounts/login/",
data=json.dumps(udata),
headers=self.headers)
to
response = self.client.post("/accounts/login/",
json=udata,
headers=self.headers)
… to get the appropriate json headers. Or use:
response = self.client.post("/accounts/login/",
data=udata,
headers=self.headers)
in order to send it as form-encoded data instead of json.