Pause/Delay sending of new batch of users from swarm - python-3.x

Question

I have a test case where I need to spawn 1000 websocket connections and sustain a conversation over them through a Locust task (It has a prefedined send/receive process for the websocket connections). I can successfully do it by the following setup in locust:
Max Number of Users: 1000
Hatch rate: 1000
However, this setup opens up 1000 connection every second. Even if i lower down the hatch rate, it will come to a time where it will continue to spawn 1000 websocket connections per second. Is there a way to spawn 1000 users instantly and halt/delay the swarm in sending new 1000 connections for quite some time?
I am trying to test if a my server can handle 1000 users sending and receiving messages from my server through a websocket connection. I have tried multiprocessing approach in python but I'm having a hard time to spawn connections as fast as I can with Locust.
class UserBehavior(TaskSet):
statements = [
"Do you like coffee?",
"What's your favorite book?",
"Do you invest in crypto?",
"Who will host the Superbowl next year?",
"Have you listened to the new Adele?",
"Coldplay released a new album",
"I watched the premiere of Succession season 3 last night",
"Who is your favorite team in the NBA?",
"I want to buy the new Travis Scott x Jordan shoes",
"I want a Lamborghini Urus",
"Have you been to the Philippines?",
"Did you sign up for a Netflix account?"
]
def on_start(self):
pass
def on_quit(self):
pass
#task
def send_convo(self):
end = False
ws_url = "ws://xx.xx.xx.xx:8080/websocket"
self.ws = create_connection(ws_url)
body = json.dumps({"text": "start blender"})
self.ws.send(body)
while True:
#print("Waiting for response..")
response = self.ws.recv()
if response != None:
if "Sorry, this world closed" in response:
end = True
break
if not end:
body = json.dumps({"text": "begin"})
self.ws.send(body)
while True:
#print("Waiting for response..")
response = self.ws.recv()
if response != None:
# print("[BOT]: ", response)
if "Sorry, this world closed" in response:
end = True
self.ws.close()
break
if not end:
body = json.dumps({"text": random.choice(self.statements)})
start_at = time.time()
self.ws.send(body)
while True:
response = self.ws.recv()
if response != None:
if "Sorry, this world closed" not in response:
response_time = int((time.time() - start_at)*1000)
print(f"[BOT]Response: {response}")
response_length = len(response)
events.request_success.fire(
request_type='Websocker Recv',
name='test/ws/echo',
response_time=response_time,
response_length=response_length,
)
else:
end = True
self.ws.close()
break
if not end:
body = json.dumps({"text": "[DONE]"})
self.ws.send(body)
while True:
response = self.ws.recv()
if response != None:
if "Sorry, this world closed" in response:
end = True
self.ws.close()
break
if not end:
time.sleep(1)
body = json.dumps({"text": "EXIT"})
self.ws.send(body)
time.sleep(1)
self.ws.close()
class WebsiteUser(HttpUser):
tasks = [UserBehavior]
wait_time = constant(2)
host = "ws://xx.xx.xx.xx:8080/websocket"
For this particular test, I set the maximum users to 1 and the hatch rate to 1 and clearly, locust keeps on sending 1 request per second as seen on the following responsees:
[BOT]Response: {"text": "No, I don't have a netflix account. I do have a Hulu account, though.", "quick_replies": null}
enter code here
[BOT]Response: {"text": "I have not, but I would love to go. I have always wanted to visit the Philippines.", "quick_replies": null
[BOT]Response: {"text": "No, I don't have a netflix account. I do have a Hulu account, though.", "quick_replies": null}
[BOT]Response: {"text": "I think it's going to be New Orleans. _POTENTIALLY_UNSAFE__", "quick_replies": null}
My expectation is after I set the maximum user to 1, and a hatch rate of 1, there would instantly be 1 websocket connection sending a random message, and receiving 1 main response from the websocket server. but what's happening is it keeps on repeating the task per second until i explicitly hit the stop button on the locust dashboard.

Answer 1

I would debug your logic. Put more print statements in each if block at various places and between each block. When dealing with a long list of decisions, it's easy to get things tripped up.
In this case, you are only wanting to sleep in a very specific situation but it's not happening. Most likely you're setting end = True when you're not expecting it so you're not sleeping and are immediately going to get a new user.
EDIT:
Reviewing your question and issue description again, it sounds like you expect Locust to send a single request and then never send another one. That's not how Locust works. Locust will run your task code for a user. When it's done, that user goes away and it waits for a certain amount of time (looks like you have it set to 2 seconds) and then it spawns another user and starts the task over again. The idea is it will try to keep a near constant number of users you tell it to. It will not only run 1000 users and then end the test, by default.
If you want to keep all 1000 users running, you need to make them continue to execute code. For example, you could put everything in your task in another while loop with another way to break out and end. That way even after making your socket connection and sending the single message you expect, the user will stay alive in the loop and won't end because it ran out of things to do. Doing it this way requires a lot more work and coordination but is possible. There may be other questions on SO about different approaches if this isn't exactly what you're looking for.