temporalio/temporal · error

duplicate registration of dynamic config key: %q

Error message

duplicate registration of dynamic config key: %q

What it means

register() enforces that each dynamic config Key is registered at most once; a second New*Setting call with the same key string panics. Duplicate keys would make queryRegistry ambiguous, so the failure is made loud at startup.

Source

Thrown at common/dynamicconfig/registry.go:28

		settings map[Key]GenericSetting
		queried  atomic.Bool
	}
)

var (
	globalRegistry registry
)

func register(s GenericSetting) {
	if globalRegistry.queried.Load() {
		panic("dynamicconfig.New*Setting must only be called from static initializers")
	}
	if globalRegistry.settings == nil {
		globalRegistry.settings = make(map[Key]GenericSetting)
	}
	if globalRegistry.settings[s.Key()] != nil {
		// nolint:forbidigo // only called during static initialization
		panic(fmt.Sprintf("duplicate registration of dynamic config key: %q", s.Key().String()))
	}
	globalRegistry.settings[s.Key()] = s
}

func queryRegistry(k Key) GenericSetting {
	if !globalRegistry.queried.Load() {
		globalRegistry.queried.Store(true)
	}
	return globalRegistry.settings[k]
}

// For testing only; do not call from regular code!
func ResetRegistryForTest() {
	globalRegistry.settings = nil
	globalRegistry.queried.Store(false)
}

View on GitHub (pinned to bde624efd1)

Solutions

1. Rename one of the duplicate keys so each is unique (follow the component-prefix convention, e.g. matching., history.)
2. Delete the redundant declaration if the setting already exists elsewhere
3. Search the codebase for the key string before adding a new setting

Example fix

// before (two files)
var a = NewBoolSetting("matching.flag", false, ...)
var b = NewBoolSetting("matching.flag", true, ...)
// after
var a = NewBoolSetting("matching.flag", false, ...)
var b = NewBoolSetting("matching.otherFlag", true, ...)

// grep for key before adding

When it happens

Trigger: Two packages (or two vars in one package) declaring settings with the identical key string, e.g. two copies of NewBoolSetting("history.xxx", ...) after a copy-paste or a package split; tests declaring the same key in multiple files.

Common situations: Copy-pasting a setting declaration to a new file without renaming the key; merging branches that each added a setting with the same name; re-running declarations in test binaries sharing globals.

Related errors

• dynamicconfig.New*Setting must only be called from static in
• Can't deep copy non-zero time.Time: %v
• Can't deep copy value of type %s: %v
• ConvertGradualChange can only be used with scalar types for
• unsupported error type: %v

AI-assisted analysis of temporalio/temporal@bde624efd1 (2026-09-01). Data as JSON: /api/errors/30bd0f48f306a141. Report an issue: GitHub.