example of keeping tasks on a single class

locustfile.py

from locust import HttpLocust, TaskSet, task
import json

class UserBehavior(TaskSet):

    def on_start(self):
        # this retrieves a coookie from the server and stores in in a RequestsCookieJar:  self.locust.client.cookes
        # that is, it stores the cookie on an instance of this class, not the class itself (as your code does)
        # your server may have different requirements for how the login request should look, but this worked for me
	self.client.post("/login",

                         data=json.dumps({'username':'foo',
                                          'password':'bar'}),

                         headers={'Content-Type' : 'application/json',
                                  'Accept'       : 'application/json, text/javascript, */*; q=0.01',
                                  'Connection'   : 'keep-alive'}
                  )

    @task(1)
    def do_thing(self):

        # your cookies may look differently, mine use this key:
        print(self.locust.client.cookies['internalSession']) # used to verify that n unique cookies appear
                                                             # where n is the number of users I specified in the locust gui

        # use the cookies kwarg and pass a dictionary
        # get_dict pulls a dictionary from the RequestsCookieJar
        response=self.client.get('/do/the/thing/', cookies=self.locust.client.cookies.get_dict())

        # used to visually verify that I'm getting back what I think I should
        print('    ', response.status_code, response.text)


class WebsiteUser(HttpLocust):
    task_set = UserBehavior
    min_wait = 1000
    max_wait = 9000