Side effect

workflow.SideEffect is useful for short, nondeterministic code snippets, such as getting a random value or generating a UUID. It executes the provided function once and records its result into the workflow history. workflow.SideEffect does not re-execute upon replay, but instead returns the recorded result. It can be seen as an "inline" activity. Something to note about workflow.SideEffect is that, unlike the Cadence guarantee of at-most-once execution for activities, there is no such guarantee with workflow.SideEffect. Under certain failure conditions, workflow.SideEffect can end up executing a function more than once.

The only way to fail SideEffect is to panic, which causes a decision_task failure. After the timeout, Cadence reschedules and then re-executes the decision_task, giving SideEffect another chance to succeed. Do not return any data from SideEffect other than through its recorded return value.

The following sample demonstrates how to use SideEffect:

encodedRandom := SideEffect(func(ctx cadence.Context) interface{} {
    return rand.Intn(100)
})

var random int
encodedRandom.Get(&random)
if random < 50 {
    ...
} else {
    ...
}