customizable subsystem loggers

lifecycle.go

@@ -20,14 +20,24 @@ type LifecycleOpts struct {
 // Lifecycle represents the core application structure. Lifecycle manages
 // resources providing an orchestrator for setup and teardown of sub-systems.
 type Lifecycle struct {
+	// Logger is the logger for the lifecycle. If not set, it will be initialized
+	// by the lifecycle itself using the default logger.
+	logger *slog.Logger
+
 	subsystems      []*Subsystem
 	setupTracker    map[string]bool
 	teardownTracker map[string]bool
 	opts            LifecycleOpts
 }
 
-// NewLifecycle creates a new Lifecycle instance with the given subsystems.
+// NewLifecycle creates a new Lifecycle instance with a default logger and the
-func NewLifecycle(subsystems ...*Subsystem) *Lifecycle {
+// given subsystems. It panics if any subsystem has a duplicate name.
+func NewLifecycle(defaultLogger *slog.Logger, subsystems ...*Subsystem) *Lifecycle {
+	// Use the provided logger or initialize a default one
+	if defaultLogger == nil {
+		defaultLogger = slog.Default()
+	}
+
 	// Ensure subsystems are unique
 	unique := make(map[string]bool)
 	for _, sub := range subsystems {
@@ -38,6 +48,7 @@ func NewLifecycle(subsystems ...*Subsystem) *Lifecycle {
 	}
 
 	return &Lifecycle{
+		logger:          defaultLogger,
 		subsystems:      subsystems,
 		setupTracker:    make(map[string]bool),
 		teardownTracker: make(map[string]bool),
@@ -57,14 +68,14 @@ func (app *Lifecycle) WithOpts(opts LifecycleOpts) *Lifecycle {
 func (app *Lifecycle) Setup() error {
 	setupCount := 0
 	for _, sub := range app.subsystems {
-		if ok, err := app.setupSingle(sub); err != nil {
+		if ok, err := app.setupSingle(sub, app.logger); err != nil {
 			return err
 		} else if ok {
 			setupCount++
 		}
 	}
 
-	slog.Info("Lifecycle sub-systems initialized, backend setup complete",
+	app.logger.Info("Lifecycle sub-systems initialized, backend setup complete",
 		"count", setupCount, "subsystems", mapToString(app.setupTracker))
 
 	return nil
@@ -83,17 +94,25 @@ func (app *Lifecycle) Teardown() error {
 		}
 	}
 
-	slog.Info("All sub-systems torn down, backend teardown complete",
+	app.logger.Info("All sub-systems torn down, backend teardown complete",
 		"count", teardownCount, "subsystems", mapToString(app.teardownTracker))
 
 	return nil
 }
 
 // Require adds sub-system(s) to the lifecycle and immediately runs any setup
-// function. Relevant when a sub-system is not part of the main application
+// functions. Relevant when a sub-system is not part of the main application
 // but may still be conditionally necessary. Any sub-systems that are already
 // set up are ignored.
 func (app *Lifecycle) Require(subsystems ...*Subsystem) error {
+	return app.RequireL(app.logger, subsystems...)
+}
+
+// RequireL adds sub-system(s) to the lifecycle with a specific logger and
+// immediately runs any setup functions. See Require for more details.
+// This variation is useful when you need to set up sub-systems with a non-
+// default logger.
+func (app *Lifecycle) RequireL(logger *slog.Logger, subsystems ...*Subsystem) error {
 	for _, sub := range subsystems {
 		if sub == nil {
 			return fmt.Errorf("sub-system is nil")
@@ -101,7 +120,7 @@ func (app *Lifecycle) Require(subsystems ...*Subsystem) error {
 
 		// Check if the sub-system is already set up
 		if _, ok := app.setupTracker[sub.name]; ok {
-			slog.Warn("sub-system already set up, ignoring", "subsystem", sub.name)
+			app.logger.Warn("sub-system already set up, ignoring", "subsystem", sub.name)
 			continue
 		}
 
@@ -109,22 +128,25 @@ func (app *Lifecycle) Require(subsystems ...*Subsystem) error {
 		app.subsystems = append(app.subsystems, sub)
 
 		// Run the setup function for the sub-system
-		if _, err := app.setupSingle(sub); err != nil {
+		if _, err := app.setupSingle(sub, logger); err != nil {
 			return fmt.Errorf("error setting up required subsystem '%s': %w", sub.name, err)
 		}
 	}
 
-	slog.Info("New sub-systems initialized", "all", mapToString(app.setupTracker))
+	app.logger.Info("New sub-systems initialized", "all", mapToString(app.setupTracker))
 
 	return nil
 }
 
 // setupSingle is a helper function to set up a single sub-system.
-func (app *Lifecycle) setupSingle(sub *Subsystem) (bool, error) {
+func (app *Lifecycle) setupSingle(sub *Subsystem, logger *slog.Logger) (bool, error) {
 	if sub == nil {
 		return false, fmt.Errorf("sub-system is nil")
 	}
 
+	// Set the logger for the sub-system
+	sub.logger = logger
+
 	// Check if all dependencies are satisfied
 	for _, dep := range sub.depends {
 		if _, ok := app.setupTracker[dep.name]; !ok {
@@ -132,7 +154,7 @@ func (app *Lifecycle) setupSingle(sub *Subsystem) (bool, error) {
 				return false, fmt.Errorf("dependency '%s' not satisfied for '%s'", dep.name, sub.name)
 			} else {
 				// Attempt to set up the dependency
-				if _, err := app.setupSingle(dep); err != nil {
+				if _, err := app.setupSingle(dep, logger); err != nil {
 					return false, fmt.Errorf("error setting up dependency '%s' for '%s': %w", dep.name, sub.name, err)
 				}
 

subsystem.go

@@ -1,8 +1,14 @@
 package app
 
+import (
+	"fmt"
+	"log/slog"
+)
+
 // Subsystem represents a sub-system of the application, with its setup and
 // teardown functions and dependencies.
 type Subsystem struct {
+	logger   *slog.Logger
 	name     string
 	setup    setupFn
 	teardown teardownFn
@@ -28,3 +34,11 @@ func NewSubsystem(name string, opts SubsystemOpts) *Subsystem {
 		depends:  opts.Depends,
 	}
 }
+
+// Logger returns the logger for the subsystem.
+func (s *Subsystem) Logger() *slog.Logger {
+	if s.logger == nil {
+		panic(fmt.Sprintf("subsytem %s used before logger was initialized", s.name))
+	}
+	return s.logger
+}