antigravity-skills-reference/web-app/public/skills/dbos-golang/references/workflow-determinism.md

title, impact, impactDescription, tags

title	impact	impactDescription	tags
Keep Workflows Deterministic	CRITICAL	Non-deterministic workflows cannot recover correctly	workflow, determinism, recovery, reliability

Keep Workflows Deterministic

Workflow functions must be deterministic: given the same inputs and step return values, they must invoke the same steps in the same order. Non-deterministic operations must be moved to steps.

Incorrect (non-deterministic workflow):

func exampleWorkflow(ctx dbos.DBOSContext, input string) (string, error) {
	// Random value in workflow breaks recovery!
	// On replay, rand.Intn returns a different value,
	// so the workflow may take a different branch.
	if rand.Intn(2) == 0 {
		return stepOne(ctx)
	}
	return stepTwo(ctx)
}

Correct (non-determinism in step):

func exampleWorkflow(ctx dbos.DBOSContext, input string) (string, error) {
	// Step result is checkpointed - replay uses the saved value
	choice, err := dbos.RunAsStep(ctx, func(ctx context.Context) (int, error) {
		return rand.Intn(2), nil
	}, dbos.WithStepName("generateChoice"))
	if err != nil {
		return "", err
	}
	if choice == 0 {
		return stepOne(ctx)
	}
	return stepTwo(ctx)
}

Non-deterministic operations that must be in steps:

• Random number generation
• Getting current time (time.Now())
• Accessing external APIs (http.Get, etc.)
• Reading files
• Database queries

Reference: Workflow Determinism