How to handle API calls in a row in Locust ?

[chunji08]

Prerequisites

• I am using the latest version of Locust
• I am suggesting a new feature, not asking a question

Description

In my test case, I am trying to make multiple API calls in a sequence, where the current API call's URL value is from the previous call's response body

Here is my current code:

from locust import User, task, between, events

class SAMLUser(User):
    wait_time = between(5, 9)

    @task
    def idpfdc_sequence(self):
        idp_redirect_url = "..." 
        response1 = self.client.get(idp_redirect_url,headers=headers,verify=False, allow_redirects=False)

        # if current call fails, needs to restart from scratch.  
        if response1.status_code != 200:
           return

        response2 = self.client.get(response1.headers['Location'], headers=headers,verify=False, allow_redirects=False)
        
        # rest of the test sequence 
        pass 

    def on_start(self):
        # Initialization code goes here
        pass

1. If I was to have it executed with limited users, everything executed smoothly, since I did not hit the failure in the response1 API call.

2. If I was to have it executed with extra users, in some running session, the first API call hits the failure, and return back 400 code. In my current code, I was doing "return", which hopes the current session to be stopped, and a new one would be started. But I don't see it happens. What I have noticed is, all the API call hangs until the time running out.

3. So I have tried this instead of "return",
   raise StopUser("1st API call fails!")

I do see the tests are keep going, and the 2nd API calls are being executed until the time-out. But In the locust "number of user" diagram, I am getting this,

As if it decrease the number of users, to make the testing moving .

So I guess my question are,
A) Is "return" the correct solution in such case ?
B) If I was to use StopUser(..), is there a way for me to spawn a new user on the fly ?
C) Any better solutions for my case ?

Thanks,

Jack

[cyberw]

If I was to have it executed with extra users, in some running session, the first API call hits the failure, and return back 400 code. In my current code, I was doing "return", which hopes the current session to be stopped, and a new one would be started. But I don't see it happens. What I have noticed is, all the API call hangs until the time running out.

What do you mean "the api call hangs until the time running out"?

I recommend running the test in a debugger or adding some print statements.

a) return is fine, should work pretty much the way you expect, unless you mean you want to run on_start again
b) dont throw StopUser, it is an internal thing (we should probably rename it _StopUser or something...)
c) not really. The one thing that I think you may be confused about is the fact that Users loop forever. Their session is never terminated and on_start only happens once. If you need fine grained control use a flag:

class MyUser(HttpUser):
    first_run = True

    @task
    def t(self):
        if self.first_run:
            self.first_run = False
            # Initialization code goes here      
        ...
        # if current call fails, needs to restart from scratch.  
        if response1.status_code != 200:
           self.first_run = True
           return

Another way to do it is just to call on start directly:

    # if current call fails, needs to restart from scratch.  
    if response1.status_code != 200:
       self.on_start()
       return

[chunji08]

What do you mean "the api call hangs until the time running out"?

In the middle my Locust running, if the response1 failure happened, and I had it "return", then till the end of this locust running, I don't see any extra response1 or response2 calls are made.

Thanks for the tips, I will give a try.

Thanks.

Jack

[github-actions]

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