Thread Safety of TypeScript Async Calls in Custom Exec Steps

Gatling (Open-Source)
1

Gatling version: 3.14.700
Gatling flavor: TypeScript
Build tool: npm

Context: I’m writing load tests using the TypeScript DSL to simulate front-end interactions with our backend. Some of these interactions involve complex business logic that’s already implemented in our front-end team’s TypeScript SDK.

Challenge: Rather than reimplementing and maintaining duplicate logic in the load tests, I’d like to reuse the existing SDK directly within custom exec steps since I have no need to monitor these specific calls as part of the load test. However, I have concerns about thread safety.

Technical Question: I understand that blocking code in custom exec blocks should be avoided since they execute in a shared thread pool across virtual users. The SDK methods are all defined as async functions in TypeScript.

My question is: How does Gatling’s Scala engine handle TypeScript async/await operations in custom exec steps?

Specifically:

  • Are TypeScript async calls safe to use without blocking other virtual users?

  • How does the JavaScript event loop model translate to the JVM threading model during test execution?

  • Are there any best practices or pitfalls I should be aware of when using async TypeScript SDK calls in custom exec steps?

Use Case Example:

typescript

// Simplified example
exec(async (session) => {
  const result = await frontendSDK.complexOperation(session.get('data'));
  return session.set('processedData', result);
})

Any insights into the threading model and execution context would be greatly appreciated!

Thanks in advance!

2

After some experiment my question is in fact far more simple than expected :

Is there a way to introduce an async call in a custom exec call since the function inside it can’t be set as async, and can’t return a Promise ?

And if only there is a way to achieve this, my first interrogation on “is it safe to do” will have a reason to exist :slight_smile: