temporalio/temporal · warning

failed to get caller info for metric definition

Error message

failed to get caller info for metric definition

What it means

newMetricDefinition uses runtime.Caller(2) to record the source file and line where a metric was declared, for debugging/metric-attribution purposes. If runtime.Caller fails to walk the stack (extremely rare; can happen with inlined or manipulated stacks, e.g. runtime tricks, -gcflags=-l mismatches, or calling via reflect/assembly wrappers), the library panics. It is a programmer-error invariant, not a runtime condition.

Source

Thrown at common/metrics/defs_base.debug.go:26

// metricDefinition contains the definition for a metric
type metricDefinition struct {
	name        string
	description string
	unit        MetricUnit
	file        string
	line        int
}

func newMetricDefinition(name string, opts ...Option) metricDefinition {
	d := metricDefinition{
		name:        name,
		description: "",
		unit:        "",
	}
	_, file, line, ok := runtime.Caller(2)
	if !ok {
		panic("failed to get caller info for metric definition")
	}
	d.file = file
	d.line = line
	for _, opt := range opts {
		opt.apply(&d)
	}
	return d
}

func (md metricDefinition) Name() string {
	return md.name
}

func (md metricDefinition) Unit() MetricUnit {
	return md.unit
}

func (md metricDefinition) File() string {

View on GitHub (pinned to bde624efd1)

Solutions

1. Check that metric definitions are created directly through the provided constructor/vars helpers, not through extra intermediate wrappers that shift the stack depth
2. If you added a wrapper layer, adjust the runtime.Caller depth in defs_base.debug.go accordingly
3. Rebuild without nonstandard compiler flags that may suppress inlining assumptions
4. Report upstream if it reproduces with stock metric definition calls

Example fix

// before
_, file, line, ok := runtime.Caller(2)
if !ok {
	panic("failed to get caller info for metric definition")
}
// after
_, file, line, ok := runtime.Caller(1) // depth adjusted for new wrapper layer
if !ok {
	file, line = "unknown", 0 // degrade gracefully instead of panicking
}

When it happens

Trigger: Defining a metric via newMetricDefinition (any metric definition constructor) in a context where runtime.Caller(2) returns ok=false — practically only when the call stack is shorter than expected or the code path is invoked through non-standard stack manipulation.

Common situations: Refactoring metric definition helpers so the stack depth no longer matches the hardcoded Caller(2) offset; unusual build flags affecting inlining; exotic code generation wrappers.

Related errors

• not implemented
• unable to create metrics handler: %w
• Current cluster name is empty
• Version increment <= 0 or > 2147483647
• <dynamic updateVersionToClusterName err>

AI-assisted analysis of temporalio/temporal@bde624efd1 (2026-09-01). Data as JSON: /api/errors/204a575fae182232. Report an issue: GitHub.