# 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
if random < 50 {
} else {