We recently had a customer from a large clothing retailer ask us if there was any way to ensure that data, such as a username/password combination, could be restricted such that it was “checked out” and available only for a specific concurrent user. This is very common with logins, where systems often will prevent concurrent logins from multiple IP addresses.

While BrowserMob does not have a concept in which data rows can be “checked out”, some simple scripting can achieve the same results. The key is in creative use of the browserMob.getUserNum() and browserMob.getTxCount() APIs. You can learn more about them by reading up on the BrowserMob APIs.

The getUserNum function returns 0, 1, 2, etc based on the concurrent user in your load test. So if you have a 100 user test, getUserNum will return between 0 and 99. It’s important to understand that it will return the same value for the same user throughout the test.

The getTxCount function returns 1, 2, 3, etc based on the number of cycles for that specific user. This number will effectively be a counter of the unique number of transactions that that particular user has executed. So user 1 and user 100 will both have a getTxCount of 1 returned, but by the time user 100 sees it, user 1 might already be on transaction 50.

Now suppose you want to run a 1000 user test in which you never concurrently log in with the same user. All you need to do is pre-create 1000 user accounts and then write your script like so:

var userId = browserMob.getUserNum();
var username = "test-" + userId;
var password = "password";
selenium.type("username", username);
selenium.type("password", password);

This works great, but what if you want to use more than 1000 logins? Suppose you want to use up to 10,000 logins among the 1000 user test? This is where the getTxCount function comes in to:

var loginsPerUser = 10;
var userNum = browserMob.getUserNum();
var txCount = browserMob.getTxCount();
var userId = userNum * loginsPerUser + txCount % loginsPerUser;
var username = "test-" + userId;
var password = "password";
selenium.type("username", username);
selenium.type("password", password);

What this does is allocate 10 logins per concurrent user. So user 1 will get usernames test-0, test-1, …, test-9 while user 8 will get usernames test-80, test-81, …, test-89, etc. Because of the mod call (%) the ten usernames will simply wrap around once they’ve been used.

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API · Scripting