apache/beam · error

expected 2 options, got

Error message

expected 2 options, got %v: %v

What it means

The diagnostics hook's Init expects exactly two options: heapProfileSamplingFrequencySeconds and another sampling frequency. Any option count other than 0 or 2 produces this error listing the count and values received.

Solutions

1. Pass exactly two integer options: heap profile and goroutine profile sampling frequencies in seconds, e.g. "30,30".
2. Remove trailing commas or whitespace that can split into extra options.
3. Leave options empty to disable the hook (len==0 accepted).
4. Verify the runner's flag construction matches the current SDK hook option format.

Example fix

// before
--diagnostics_sampling_frequency="30"
// after
--diagnostics_sampling_frequency="30,30"

opts := strings.Split(diagOpt, ",")
if len(opts) != 2 { return fmt.Errorf("diagnostics hook needs exactly 2 options, got %d", len(opts)) }
for _, o := range opts { if _, err := strconv.Atoi(strings.TrimSpace(o)); err != nil { return err } }

if err := hook.Init(ctx); err != nil {
	log.Fatalf("diagnostics hook option error: %v", err)
}

When it happens

Trigger: Configuring the diagnostics hook (diagnostics_sampling_frequency style options) with 1 or 3+ values, e.g. only "30" without the second frequency, or trailing separators producing extra empty options.

Common situations: Workers launched with incomplete option strings, trailing commas, or format changes between Beam versions that altered the expected option count.

Understand the failure class

Background: "Must pass :limit option" / "Missing required option" — required option errors explained — this error's family across 41 libraries.

Related errors

• expected 1 option, got
• expected 1 option, got
• max time between dumps
• sample period should be greater than 1ms, got
• bad coder kind

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/22a71dc0111f6146. Report an issue: GitHub.

Appendix: source

Thrown at sdks/go/pkg/beam/core/runtime/harness/diagnostics_hook.go:39

	"strconv"

	"github.com/apache/beam/sdks/v2/go/pkg/beam/core/util/hooks"
)

var (
	samplingFrequencySeconds   int = 1
	maxTimeBetweenDumpsSeconds int = 60
)

func init() {
	hf := func(opts []string) hooks.Hook {
		return hooks.Hook{
			Init: func(ctx context.Context) (context.Context, error) {
				if len(opts) == 0 {
					return ctx, nil
				}
				if len(opts) < 2 || len(opts) > 2 {
					return ctx, fmt.Errorf("expected 2 options, got %v: %v", len(opts), opts)
				}

				heapProfileSamplingFrequencySeconds, err := strconv.Atoi(opts[0])
				if err != nil {
					return nil, err
				}
				heapProfileMaxTimeBetweenDumpsSeconds, err := strconv.Atoi(opts[1])
				if err != nil {
					return nil, err
				}
				samplingFrequencySeconds = heapProfileSamplingFrequencySeconds
				maxTimeBetweenDumpsSeconds = heapProfileMaxTimeBetweenDumpsSeconds

				return ctx, nil
			},
		}
	}
	hooks.RegisterHook("beam:go:hook:diagnostics:heapDump", hf)

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