Simulate delay in workloads

[Wonshtrum]

I'm working on simulation integration, and I was wondering if it would be possible to simulate a delay in a workload?
The relevant function to call seems to be:

foundationdb/flow/include/flow/flow.h

Line 1570 in 351883d

inline Future<Void> delay(double seconds, TaskPriority taskID = TaskPriority::DefaultDelay) {

But it is not exposed in fdb_c bindings.
I also tried to directly access g_network from the workload, but this symbol is marked local/hidden, so it is unavailable from the shared object.
Is there another way to do something like this?
If not, could we add a binding in fdb_c like:

FDBFuture* fdb_delay(double seconds);

Another solution would be to add a similar function to the FDBWorkloadContext.
Finally, we could add a way to get direct access to g_network from FDBWorkloadContext. While great for some prototyping, it would be very unsafe/unstable, and would only work with C++ workloads compiled in the official docker, and not compatible with the new C API.

[xis19]

I can have a look if I have spare time by luck, but it would be interesting to see what is your use case. Can you elaborate a bit more about what you are trying to do? It might be possible that you do not need this delay.

[Wonshtrum]

We want to implement new workloads with time-related faults to test time-sensitive layers.
This would be helpful to test, for example:

• systems with asynchronous tasks
• layers with TTL on records
• leader elections

Having the possibility to add an arbitrary additional delay for some workers, on top of the FoundationDB faults, would be great.
Something as simple as:

if buggify {
    delay(1.0).await;
}

[spraza]

We want to implement new workloads with time-related faults to test time-sensitive layers. This would be helpful to test, for example:

• systems with asynchronous tasks
• layers with TTL on records
• leader elections

Having the possibility to add an arbitrary additional delay for some workers, on top of the FoundationDB faults, would be great. Something as simple as:

if buggify {
delay(1.0).await;
}

Agreed, we use delay for all sort of testing in FDB simulation.