LoadTestShape

[sribatchu]

Can you run a LoadTestShape class in lambda? Specifically a case for ramping up and ramping down users at different stages?

[FutureSharks]

There's no reason why not

[sribatchu]

when running it as lambda, it always seem to ignore the LoadTestShape and just uses the num_users and spawn_rate from the event payload. If I don't pass num_users or spawn_rate as part of my event payload, I get Locust exception Exception('configuration error, attribute not set: num_users')

lambda.py

def lambda_handler(event, context=None):
    try:
        if event:
            settings = create_settings(**event)
        else:
            settings = create_settings(from_environment=True)

        loadtest = LocustLoadTest(settings)
        loadtest.run()
    except Exception as e:
        logging.error("Locust exception {0}".format(repr(e)))

    else:
        locust_stats = loadtest.stats()
        lambda_runtime_info = get_lambda_runtime_info(context)
        loadtest_results = locust_stats.copy()
        loadtest_results.update(lambda_runtime_info)
        json_results = json.dumps(loadtest_results)

        logging.info(json_results)
        return json_results

locustfile.py

class LoadTest(HttpUser):
    wait_time = between(0, 1)
    @task
    def query(self):
        self.client.get("/api")

class StagesShapeWithCustomUsers(LoadTestShape):
    stages = [
        {"duration": 10, "users": 100, "spawn_rate": 10, "user_classes": [LoadTest]},
        {"duration": 20, "users": 150, "spawn_rate": 10, "user_classes": [LoadTest]},
        {"duration": 30, "users": 200, "spawn_rate": 10, "user_classes": [LoadTest]}
    ]

    def tick(self):
        run_time = self.get_run_time()
        for stage in self.stages:
            if run_time < stage["duration"]:
                try:
                    tick_data = (stage["users"], stage["spawn_rate"], stage["user_classes"])
                except KeyError:
                    tick_data = (stage["users"], stage["spawn_rate"])
                return tick_data
        return None

[FutureSharks]

Hi @sribatchu,

it always seem to ignore the LoadTestShape and just uses the num_users and spawn_rate from the event payload

Hmmm, I see.

I've just thought about it and even if we do manage to find and use the LoadTestShape class, it still won't work because it counts the time since the load test started. This will never work on Lambda in its current implementation as the counter would be restarted for every lambda invocation.

The only way it could theoretically work is if invokust saved the start time externally and then counted the time using this external record. This would require a custom LoadTestShape class just for invokust though. PRs welcome 🙂