What causes "resource.ParseCPUCount: unable to parse %q: %v" in apache/beam?

Supply a plain non-negative decimal integer string, e.g. '4'

resource.ParseCPUCount: unable to parse %q: %v

Error message

resource.ParseCPUCount: unable to parse %q: %v

What it means

ParseCPUCount converts a string to an unsigned 64-bit CPU count via strconv.ParseUint(v, 10, 64). If the value is not a valid non-negative integer it panics with 'resource.ParseCPUCount: unable to parse %q: %v'.

Source

Thrown at sdks/go/pkg/beam/options/resource/hint.go:259

func (h acceleratorHint) MergeWithOuter(outer Hint) Hint {
	return h
}

func (h acceleratorHint) String() string {
	return fmt.Sprintf("accelerator=%v", h.value)
}

// ParseCPUCount converts a number in string form into a hint.
// An invalid format will cause ParseCPUCount to panic.
//
// Hints are advisory only and runners may not respect them.
//
// See https://beam.apache.org/documentation/runtime/resource-hints/ for more information about
// resource hints.
func ParseCPUCount(v string) Hint {
	b, err := strconv.ParseUint(v, 10, 64)
	if err != nil {
		panic(fmt.Sprintf("resource.ParseCPUCount: unable to parse %q: %v", v, err))
	}
	return CPUCount(uint64(b))
}

// CPUCount hints that this scope should be put in a machine with at least this many CPUs or vCPUs.
//
// Hints are advisory only and runners may not respect them.
//
// See https://beam.apache.org/documentation/runtime/resource-hints/ for more information about
// resource hints.
func CPUCount(v uint64) Hint {
	return CPUCountHint{value: uint64(v)}
}

type CPUCountHint struct {
	value uint64
}

View on GitHub (pinned to 12126d8942)

Solutions

Supply a plain non-negative decimal integer string, e.g. '4'
Trim whitespace and remove unit suffixes like 'cores' or 'vCPU'
Guard with strconv.ParseUint in the caller before constructing the hint

Example fix

// before
resource.ParseCPUCount("-2")
// after
resource.ParseCPUCount("4")

Defensive patterns

Strategy: validation

Validate before calling

if n, err := strconv.ParseUint(v, 10, 64); err != nil {
    return fmt.Errorf("invalid cpu count %q", v)
}

Try / catch

defer func() {
    if r := recover(); r != nil {
        err = fmt.Errorf("ParseCPUCount rejected value: %v", r)
    }
}()

Prevention

Pass non-negative decimal integer strings only
Remove unit suffixes like 'cores'/'vCPU' before parsing
Handle unset config by substituting a default before calling ParseCPUCount

When it happens

Trigger: Calling resource.ParseCPUCount with a non-integer, negative number ('-2'), or out-of-range value, or feeding such a value through --resource_hints=cpu_count=<bad>.

Common situations: Passing '4 cores', a negative value, or an empty string from an unset flag/env var into the hint.

Understand the failure class

Background: "Invalid ... format", "must be in format X", "does not look like a ..." — invalid argument format errors across CLI tools and libraries — this error's family across 17 libraries.

Parsing and encoding errors: unexpected token, malformed input — why parsers reject input and how to find the real culprit.

Related errors

AI-assisted analysis of apache/beam@12126d8942 (2026-09-13). Data as JSON: /api/errors/48b46facaeaa6f83. Report an issue: GitHub.