Bootstrapper functional options

The github.com/go-nacelle/nacelle package provides the following functional options to supply the bootstrapper constructor.

The following options can be supplied to the bootstrapper to tune its behavior.

WithContextFilter

WithContextFilter sets a function that accepts a context object and returns a possibly modified context object after the initial health, log, service, and configuration objects are inserted. This allows the user to add additional objects available to all processes prior to initialization.

WithConfigSourcer

WithConfigSourcer changes the default source for configuration variables. The default sourcer is the application environment using the name given to the bootstrapper as a prefix.

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func main() {
	configSourcer := config.NewFileSourcer("config.toml", config.ParseTOML)

	nacelle.NewBootstrapper(
		"example",
		setup,
		nacelle.WithConfigSourcer(configSourcer),
	).BootAndExit()
}

func setup(processes nacelle.ProcessContainer, services nacelle.ServiceContainer) error { /* ... */ }

WithConfigMaskedKeys

WithConfigMaskedKeys sets the keys to mask from log messages when loading configuration data. This is used to hide sensitive configuration values.

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func main() {
	nacelle.NewBootstrapper(
		"example",
		setup,
		nacelle.WithConfigMaskedKeys([]string{"GITHUB_ACCESS_TOKEN"}),
	).BootAndExit()
}

func setup(processes nacelle.ProcessContainer, services nacelle.ServiceContainer) error { /* ... */ }

WithLoggingInitFunc

WithLoggingInitFunc sets the factory used to create the base logger. This can be set to supply a different log backend.

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func main() {
	// This matches the default behavior, using go-nacelle/log
	initLogger := func(config *nacelle.Config) (nacelle.Logger, error) {
		c := &log.Config{}
		if err := config.Load(c); err != nil {
			return nil, fmt.Errorf("could not load logging config (%s)", err.Error())
		}

		return log.InitLogger(c)
	}

	nacelle.NewBootstrapper(
		"example",
		setup,
		nacelle.WithLoggingInitFunc(initLogger),
	).BootAndExit()
}

func setup(processes nacelle.ProcessContainer, services nacelle.ServiceContainer) error { /* ... */ }

WithLoggingFields

WithLoggingFields adds additional fields to every log message. This can be useful to present build information (time, hash, branch), process name, or operating environment.

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func main() {
	nacelle.NewBootstrapper(
		"example",
		setup,
		nacelle.WithLoggingFields(nacelle.LogFields{
			"instance_id": uuid.New(),
			"instance_start": time.Now().UTC(),
		}),
	).BootAndExit()
}

func setup(processes nacelle.ProcessContainer, services nacelle.ServiceContainer) error { /* ... */ }