52 lines
1.5 KiB
Markdown
52 lines
1.5 KiB
Markdown
---
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title: Keep Workflows Deterministic
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impact: CRITICAL
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impactDescription: Non-deterministic workflows cannot recover correctly
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tags: workflow, determinism, recovery, reliability
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---
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## Keep Workflows Deterministic
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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.
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**Incorrect (non-deterministic workflow):**
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```go
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func exampleWorkflow(ctx dbos.DBOSContext, input string) (string, error) {
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// Random value in workflow breaks recovery!
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// On replay, rand.Intn returns a different value,
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// so the workflow may take a different branch.
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if rand.Intn(2) == 0 {
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return stepOne(ctx)
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}
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return stepTwo(ctx)
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}
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```
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**Correct (non-determinism in step):**
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```go
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func exampleWorkflow(ctx dbos.DBOSContext, input string) (string, error) {
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// Step result is checkpointed - replay uses the saved value
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choice, err := dbos.RunAsStep(ctx, func(ctx context.Context) (int, error) {
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return rand.Intn(2), nil
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}, dbos.WithStepName("generateChoice"))
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if err != nil {
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return "", err
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}
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if choice == 0 {
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return stepOne(ctx)
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}
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return stepTwo(ctx)
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}
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```
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Non-deterministic operations that must be in steps:
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- Random number generation
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- Getting current time (`time.Now()`)
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- Accessing external APIs (`http.Get`, etc.)
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- Reading files
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- Database queries
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Reference: [Workflow Determinism](https://docs.dbos.dev/golang/tutorials/workflow-tutorial#determinism)
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