feat: Circuit breaker for failing domains

cmd/collect_website.go

@@ -3,8 +3,11 @@ package cmd
 import (
 	"fmt"
 	"os"
+	"time"
 
+	"github.com/Snider/Borg/pkg/circuitbreaker"
 	"github.com/schollz/progressbar/v3"
+	"golang.org/x/exp/slog"
 	"github.com/Snider/Borg/pkg/compress"
 	"github.com/Snider/Borg/pkg/tim"
 	"github.com/Snider/Borg/pkg/trix"
@@ -38,6 +41,11 @@ func NewCollectWebsiteCmd() *cobra.Command {
 			format, _ := cmd.Flags().GetString("format")
 			compression, _ := cmd.Flags().GetString("compression")
 			password, _ := cmd.Flags().GetString("password")
+			noCircuitBreaker, _ := cmd.Flags().GetBool("no-circuit-breaker")
+			circuitFailures, _ := cmd.Flags().GetInt("circuit-failures")
+			circuitCooldown, _ := cmd.Flags().GetDuration("circuit-cooldown")
+			circuitSuccessThreshold, _ := cmd.Flags().GetInt("circuit-success-threshold")
+			circuitHalfOpenRequests, _ := cmd.Flags().GetInt("circuit-half-open-requests")
 
 			if format != "datanode" && format != "tim" && format != "trix" {
 				return fmt.Errorf("invalid format: %s (must be 'datanode', 'tim', or 'trix')", format)
@@ -51,7 +59,25 @@ func NewCollectWebsiteCmd() *cobra.Command {
 				bar = ui.NewProgressBar(-1, "Crawling website")
 			}
 
-			dn, err := website.DownloadAndPackageWebsite(websiteURL, depth, bar)
+			logger := slog.New(slog.NewTextHandler(os.Stderr, &slog.HandlerOptions{
+				Level: slog.LevelInfo,
+			}))
+
+			opts := website.DownloadOptions{
+				URL:                  websiteURL,
+				MaxDepth:             depth,
+				ProgressBar:          bar,
+				EnableCircuitBreaker: !noCircuitBreaker,
+				CBSettings: circuitbreaker.Settings{
+					FailureThreshold: circuitFailures,
+					SuccessThreshold: circuitSuccessThreshold,
+					Cooldown:         circuitCooldown,
+					HalfOpenRequests: circuitHalfOpenRequests,
+					Logger:           logger,
+				},
+			}
+
+			dn, err := website.DownloadAndPackageWebsite(opts)
 			if err != nil {
 				return fmt.Errorf("error downloading and packaging website: %w", err)
 			}
@@ -104,5 +130,10 @@ func NewCollectWebsiteCmd() *cobra.Command {
 	collectWebsiteCmd.PersistentFlags().String("format", "datanode", "Output format (datanode, tim, or trix)")
 	collectWebsiteCmd.PersistentFlags().String("compression", "none", "Compression format (none, gz, or xz)")
 	collectWebsiteCmd.PersistentFlags().String("password", "", "Password for encryption")
+	collectWebsiteCmd.Flags().Bool("no-circuit-breaker", false, "Disable the circuit breaker")
+	collectWebsiteCmd.Flags().Int("circuit-failures", 5, "Number of failures to trip the circuit breaker")
+	collectWebsiteCmd.Flags().Duration("circuit-cooldown", 30*time.Second, "Cooldown time for the circuit breaker")
+	collectWebsiteCmd.Flags().Int("circuit-success-threshold", 2, "Number of successes to close the circuit breaker")
+	collectWebsiteCmd.Flags().Int("circuit-half-open-requests", 1, "Number of test requests in half-open state")
 	return collectWebsiteCmd
 }

cmd/collect_website_test.go

@@ -8,13 +8,12 @@ import (
 
 	"github.com/Snider/Borg/pkg/datanode"
 	"github.com/Snider/Borg/pkg/website"
-	"github.com/schollz/progressbar/v3"
 )
 
 func TestCollectWebsiteCmd_Good(t *testing.T) {
 	// Mock the website downloader
 	oldDownloadAndPackageWebsite := website.DownloadAndPackageWebsite
-	website.DownloadAndPackageWebsite = func(startURL string, maxDepth int, bar *progressbar.ProgressBar) (*datanode.DataNode, error) {
+	website.DownloadAndPackageWebsite = func(opts website.DownloadOptions) (*datanode.DataNode, error) {
 		return datanode.New(), nil
 	}
 	defer func() {
@@ -35,7 +34,7 @@ func TestCollectWebsiteCmd_Good(t *testing.T) {
 func TestCollectWebsiteCmd_Bad(t *testing.T) {
 	// Mock the website downloader to return an error
 	oldDownloadAndPackageWebsite := website.DownloadAndPackageWebsite
-	website.DownloadAndPackageWebsite = func(startURL string, maxDepth int, bar *progressbar.ProgressBar) (*datanode.DataNode, error) {
+	website.DownloadAndPackageWebsite = func(opts website.DownloadOptions) (*datanode.DataNode, error) {
 		return nil, fmt.Errorf("website error")
 	}
 	defer func() {

examples/collect_website/main.go

@@ -11,7 +11,12 @@ func main() {
 	log.Println("Collecting website...")
 
 	// Download and package the website.
-	dn, err := website.DownloadAndPackageWebsite("https://example.com", 2, nil)
+	opts := website.DownloadOptions{
+		URL:                  "https://example.com",
+		MaxDepth:             2,
+		EnableCircuitBreaker: true,
+	}
+	dn, err := website.DownloadAndPackageWebsite(opts)
 	if err != nil {
 		log.Fatalf("Failed to collect website: %v", err)
 	}

go.mod

@@ -61,6 +61,7 @@ require (
 	github.com/wailsapp/mimetype v1.4.1 // indirect
 	github.com/xanzy/ssh-agent v0.3.3 // indirect
 	golang.org/x/crypto v0.44.0 // indirect
+	golang.org/x/exp v0.0.0-20240719175910-8a7402abbf56 // indirect
 	golang.org/x/sys v0.38.0 // indirect
 	golang.org/x/term v0.37.0 // indirect
 	golang.org/x/text v0.31.0 // indirect

pkg/circuitbreaker/circuitbreaker.go

@@ -0,0 +1,160 @@
+
+package circuitbreaker
+
+import (
+	"fmt"
+	"io"
+	"sync"
+	"time"
+
+	"golang.org/x/exp/slog"
+)
+
+// State represents the state of the circuit breaker.
+type State int
+
+const (
+	// ClosedState is the initial state of the circuit breaker.
+	ClosedState State = iota
+	// OpenState is the state when the circuit breaker is tripped.
+	OpenState
+	// HalfOpenState is the state when the circuit breaker is testing for recovery.
+	HalfOpenState
+)
+
+// String returns the string representation of the state.
+func (s State) String() string {
+	switch s {
+	case ClosedState:
+		return "CLOSED"
+	case OpenState:
+		return "OPEN"
+	case HalfOpenState:
+		return "HALF-OPEN"
+	default:
+		return "UNKNOWN"
+	}
+}
+
+// Settings configures the circuit breaker.
+type Settings struct {
+	// FailureThreshold is the number of consecutive failures before opening the circuit.
+	FailureThreshold int
+	// SuccessThreshold is the number of consecutive successes to close the circuit.
+	SuccessThreshold int
+	// Cooldown is the time to wait in the open state before transitioning to half-open.
+	Cooldown time.Duration
+	// HalfOpenRequests is the number of test requests to allow in the half-open state.
+	HalfOpenRequests int
+	// Logger is the logger to use for state changes.
+	Logger *slog.Logger
+}
+
+// CircuitBreaker is a state machine that prevents repeated calls to a failing service.
+type CircuitBreaker struct {
+	settings         Settings
+	domain           string
+	mu               sync.Mutex
+	state            State
+	failures         int
+	successes        int
+	halfOpenRequests int
+	lastError        error
+	expiry           time.Time
+}
+
+// New creates a new CircuitBreaker.
+func New(domain string, settings Settings) *CircuitBreaker {
+	if settings.Logger == nil {
+		settings.Logger = slog.New(slog.NewTextHandler(io.Discard, &slog.HandlerOptions{
+			Level: slog.LevelError,
+		}))
+	}
+	return &CircuitBreaker{
+		settings: settings,
+		domain:   domain,
+		state:    ClosedState,
+	}
+}
+
+// Execute runs the given function, protected by the circuit breaker.
+func (cb *CircuitBreaker) Execute(fn func() (interface{}, error)) (interface{}, error) {
+	cb.mu.Lock()
+	defer cb.mu.Unlock()
+
+	switch cb.state {
+	case OpenState:
+		if time.Now().After(cb.expiry) {
+			cb.setState(HalfOpenState)
+			return cb.executeHalfOpen(fn)
+		}
+		return nil, fmt.Errorf("circuit is open for: %w", cb.lastError)
+	case HalfOpenState:
+		return cb.executeHalfOpen(fn)
+	default: // ClosedState
+		return cb.executeClosed(fn)
+	}
+}
+
+func (cb *CircuitBreaker) executeClosed(fn func() (interface{}, error)) (interface{}, error) {
+	res, err := fn()
+	if err != nil {
+		cb.failures++
+		if cb.failures >= cb.settings.FailureThreshold {
+			cb.lastError = err
+			cb.setState(OpenState)
+		}
+		return nil, err
+	}
+
+	cb.failures = 0
+	return res, nil
+}
+
+func (cb *CircuitBreaker) executeHalfOpen(fn func() (interface{}, error)) (interface{}, error) {
+	if cb.halfOpenRequests >= cb.settings.HalfOpenRequests {
+		return nil, fmt.Errorf("circuit is half-open, test requests exhausted: %w", cb.lastError)
+	}
+	cb.halfOpenRequests++
+
+	res, err := fn()
+	if err != nil {
+		cb.lastError = err
+		cb.setState(OpenState)
+		return nil, err
+	}
+
+	cb.successes++
+	// If enough test requests succeed, close the circuit.
+	if cb.successes >= cb.settings.SuccessThreshold {
+		cb.setState(ClosedState)
+	}
+
+	return res, nil
+}
+
+func (cb *CircuitBreaker) setState(state State) {
+	if cb.state == state {
+		return
+	}
+
+	cb.state = state
+	logMessage := fmt.Sprintf("Circuit %s for %s", state, cb.domain)
+	if state == OpenState {
+		cb.settings.Logger.Warn(logMessage)
+	} else {
+		cb.settings.Logger.Info(logMessage)
+	}
+
+	switch state {
+	case OpenState:
+		cb.expiry = time.Now().Add(cb.settings.Cooldown)
+		cb.successes = 0
+	case ClosedState:
+		cb.failures = 0
+		cb.successes = 0
+	case HalfOpenState:
+		cb.failures = 0
+		cb.halfOpenRequests = 0
+	}
+}

pkg/circuitbreaker/circuitbreaker_test.go

@@ -0,0 +1,101 @@
+
+package circuitbreaker
+
+import (
+	"errors"
+	"testing"
+	"time"
+)
+
+func TestCircuitBreaker(t *testing.T) {
+	settings := Settings{
+		FailureThreshold: 2,
+		SuccessThreshold: 2,
+		Cooldown:         100 * time.Millisecond,
+		HalfOpenRequests: 2,
+	}
+	cb := New("test.com", settings)
+
+	// Initially closed
+	_, err := cb.Execute(func() (interface{}, error) {
+		return "success", nil
+	})
+	if err != nil {
+		t.Errorf("Expected success, got %v", err)
+	}
+
+	// Trip the breaker
+	_, err = cb.Execute(func() (interface{}, error) {
+		return nil, errors.New("failure 1")
+	})
+	if err == nil {
+		t.Error("Expected failure, got nil")
+	}
+	_, err = cb.Execute(func() (interface{}, error) {
+		return nil, errors.New("failure 2")
+	})
+	if err == nil {
+		t.Error("Expected failure, got nil")
+	}
+
+	// Now open
+	_, err = cb.Execute(func() (interface{}, error) {
+		return "should not be called", nil
+	})
+	if err == nil || err.Error() != "circuit is open for: failure 2" {
+		t.Errorf("Expected open circuit error, got %v", err)
+	}
+
+	// Wait for cooldown
+	time.Sleep(150 * time.Millisecond)
+
+	// Half-open, should succeed
+	_, err = cb.Execute(func() (interface{}, error) {
+		return "success", nil
+	})
+	if err != nil {
+		t.Errorf("Expected success in half-open, got %v", err)
+	}
+
+	// Still half-open, need another success
+	_, err = cb.Execute(func() (interface{}, error) {
+		return "success", nil
+	})
+	if err != nil {
+		t.Errorf("Expected success in half-open, got %v", err)
+	}
+
+	// Now closed again
+	_, err = cb.Execute(func() (interface{}, error) {
+		return "success", nil
+	})
+	if err != nil {
+		t.Errorf("Expected success in closed state, got %v", err)
+	}
+
+	// Trip again to test half-open failure
+	cb.Execute(func() (interface{}, error) {
+		return nil, errors.New("failure 1")
+	})
+	cb.Execute(func() (interface{}, error) {
+		return nil, errors.New("failure 2")
+	})
+
+	time.Sleep(150 * time.Millisecond)
+
+	// Half-open, but fail
+	_, err = cb.Execute(func() (interface{}, error) {
+		return nil, errors.New("half-open failure")
+	})
+	if err == nil {
+		t.Error("Expected failure in half-open, got nil")
+	}
+
+	// Should be open again
+	_, err = cb.Execute(func() (interface{}, error) {
+		return "should not be called", nil
+	})
+	if err == nil || err.Error() != "circuit is open for: half-open failure" {
+		t.Errorf("Expected open circuit error, got %v", err)
+	}
+}