refactor: simplify exponential backoff and refactor env (#1185)

Co-authored-by: Kévin Dunglas <kevin@dunglas.fr>

Author: withinboredom

backoff.go

@@ -0,0 +1,51 @@
+package frankenphp
+
+import (
+	"sync"
+	"time"
+)
+
+type exponentialBackoff struct {
+	backoff                time.Duration
+	failureCount           int
+	mu                     sync.RWMutex
+	maxBackoff             time.Duration
+	minBackoff             time.Duration
+	maxConsecutiveFailures int
+}
+
+// recordSuccess resets the backoff and failureCount
+func (e *exponentialBackoff) recordSuccess() {
+	e.mu.Lock()
+	e.failureCount = 0
+	e.backoff = e.minBackoff
+	e.mu.Unlock()
+}
+
+// recordFailure increments the failure count and increases the backoff, it returns true if maxConsecutiveFailures has been reached
+func (e *exponentialBackoff) recordFailure() bool {
+	e.mu.Lock()
+	e.failureCount += 1
+	if e.backoff < e.minBackoff {
+		e.backoff = e.minBackoff
+	}
+
+	e.backoff = min(e.backoff*2, e.maxBackoff)
+
+	e.mu.Unlock()
+	return e.failureCount >= e.maxConsecutiveFailures
+}
+
+// wait sleeps for the backoff duration if failureCount is non-zero.
+// NOTE: this is not tested and should be kept 'obviously correct' (i.e., simple)
+func (e *exponentialBackoff) wait() {
+	e.mu.RLock()
+	if e.failureCount == 0 {
+		e.mu.RUnlock()
+
+		return
+	}
+	e.mu.RUnlock()
+
+	time.Sleep(e.backoff)
+}

backoff_test.go

@@ -0,0 +1,41 @@
+package frankenphp
+
+import (
+	"github.com/stretchr/testify/assert"
+	"testing"
+	"time"
+)
+
+func TestExponentialBackoff_Reset(t *testing.T) {
+	e := &exponentialBackoff{
+		maxBackoff:             5 * time.Second,
+		minBackoff:             500 * time.Millisecond,
+		maxConsecutiveFailures: 3,
+	}
+
+	assert.False(t, e.recordFailure())
+	assert.False(t, e.recordFailure())
+	e.recordSuccess()
+
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+	assert.Equal(t, 0, e.failureCount, "expected failureCount to be reset to 0")
+	assert.Equal(t, e.backoff, e.minBackoff, "expected backoff to be reset to minBackoff")
+}
+
+func TestExponentialBackoff_Trigger(t *testing.T) {
+	e := &exponentialBackoff{
+		maxBackoff:             500 * 3 * time.Millisecond,
+		minBackoff:             500 * time.Millisecond,
+		maxConsecutiveFailures: 3,
+	}
+
+	assert.False(t, e.recordFailure())
+	assert.False(t, e.recordFailure())
+	assert.True(t, e.recordFailure())
+
+	e.mu.RLock()
+	defer e.mu.RUnlock()
+	assert.Equal(t, e.failureCount, e.maxConsecutiveFailures, "expected failureCount to be maxConsecutiveFailures")
+	assert.Equal(t, e.backoff, e.maxBackoff, "expected backoff to be maxBackoff")
+}

env.go

@@ -0,0 +1,74 @@
+package frankenphp
+
+// #include "frankenphp.h"
+import "C"
+import (
+	"os"
+	"strings"
+	"unsafe"
+)
+
+//export go_putenv
+func go_putenv(str *C.char, length C.int) C.bool {
+	envString := C.GoStringN(str, length)
+
+	// Check if '=' is present in the string
+	if key, val, found := strings.Cut(envString, "="); found {
+		return os.Setenv(key, val) == nil
+	}
+
+	// No '=', unset the environment variable
+	return os.Unsetenv(envString) == nil
+}
+
+//export go_getfullenv
+func go_getfullenv(threadIndex C.uintptr_t) (*C.go_string, C.size_t) {
+	thread := phpThreads[threadIndex]
+
+	env := os.Environ()
+	goStrings := make([]C.go_string, len(env)*2)
+
+	for i, envVar := range env {
+		key, val, _ := strings.Cut(envVar, "=")
+		goStrings[i*2] = C.go_string{C.size_t(len(key)), thread.pinString(key)}
+		goStrings[i*2+1] = C.go_string{C.size_t(len(val)), thread.pinString(val)}
+	}
+
+	value := unsafe.SliceData(goStrings)
+	thread.Pin(value)
+
+	return value, C.size_t(len(env))
+}
+
+//export go_getenv
+func go_getenv(threadIndex C.uintptr_t, name *C.go_string) (C.bool, *C.go_string) {
+	thread := phpThreads[threadIndex]
+
+	// Create a byte slice from C string with a specified length
+	envName := C.GoStringN(name.data, C.int(name.len))
+
+	// Get the environment variable value
+	envValue, exists := os.LookupEnv(envName)
+	if !exists {
+		// Environment variable does not exist
+		return false, nil // Return 0 to indicate failure
+	}
+
+	// Convert Go string to C string
+	value := &C.go_string{C.size_t(len(envValue)), thread.pinString(envValue)}
+	thread.Pin(value)
+
+	return true, value // Return 1 to indicate success
+}
+
+//export go_sapi_getenv
+func go_sapi_getenv(threadIndex C.uintptr_t, name *C.go_string) *C.char {
+	envName := C.GoStringN(name.data, C.int(name.len))
+
+	envValue, exists := os.LookupEnv(envName)
+	if !exists {
+		return nil
+	}
+
+	return phpThreads[threadIndex].pinCString(envValue)
+}

frankenphp.go

@@ -505,88 +505,6 @@ func ServeHTTP(responseWriter http.ResponseWriter, request *http.Request) error
 	return nil
 }
 
-//export go_putenv
-func go_putenv(str *C.char, length C.int) C.bool {
-	// Create a byte slice from C string with a specified length
-	s := C.GoBytes(unsafe.Pointer(str), length)
-
-	// Convert byte slice to string
-	envString := string(s)
-
-	// Check if '=' is present in the string
-	if key, val, found := strings.Cut(envString, "="); found {
-		if os.Setenv(key, val) != nil {
-			return false // Failure
-		}
-	} else {
-		// No '=', unset the environment variable
-		if os.Unsetenv(envString) != nil {
-			return false // Failure
-		}
-	}
-
-	return true // Success
-}
-
-//export go_getfullenv
-func go_getfullenv(threadIndex C.uintptr_t) (*C.go_string, C.size_t) {
-	thread := phpThreads[threadIndex]
-
-	env := os.Environ()
-	goStrings := make([]C.go_string, len(env)*2)
-
-	for i, envVar := range env {
-		key, val, _ := strings.Cut(envVar, "=")
-		k := unsafe.StringData(key)
-		v := unsafe.StringData(val)
-		thread.Pin(k)
-		thread.Pin(v)
-
-		goStrings[i*2] = C.go_string{C.size_t(len(key)), (*C.char)(unsafe.Pointer(k))}
-		goStrings[i*2+1] = C.go_string{C.size_t(len(val)), (*C.char)(unsafe.Pointer(v))}
-	}
-
-	value := unsafe.SliceData(goStrings)
-	thread.Pin(value)
-
-	return value, C.size_t(len(env))
-}
-
-//export go_getenv
-func go_getenv(threadIndex C.uintptr_t, name *C.go_string) (C.bool, *C.go_string) {
-	thread := phpThreads[threadIndex]
-
-	// Create a byte slice from C string with a specified length
-	envName := C.GoStringN(name.data, C.int(name.len))
-
-	// Get the environment variable value
-	envValue, exists := os.LookupEnv(envName)
-	if !exists {
-		// Environment variable does not exist
-		return false, nil // Return 0 to indicate failure
-	}
-
-	// Convert Go string to C string
-	val := unsafe.StringData(envValue)
-	thread.Pin(val)
-	value := &C.go_string{C.size_t(len(envValue)), (*C.char)(unsafe.Pointer(val))}
-	thread.Pin(value)
-
-	return true, value // Return 1 to indicate success
-}
-
-//export go_sapi_getenv
-func go_sapi_getenv(threadIndex C.uintptr_t, name *C.go_string) *C.char {
-	envName := C.GoStringN(name.data, C.int(name.len))
-
-	envValue, exists := os.LookupEnv(envName)
-	if !exists {
-		return nil
-	}
-
-	return phpThreads[threadIndex].pinCString(envValue)
-}
-
 //export go_handle_request
 func go_handle_request(threadIndex C.uintptr_t) bool {
 	select {

worker.go

@@ -26,10 +26,6 @@ type worker struct {
 	ready       chan struct{}
 }
 
-const maxWorkerErrorBackoff = 1 * time.Second
-const minWorkerErrorBackoff = 100 * time.Millisecond
-const maxWorkerConsecutiveFailures = 6
-
 var (
 	watcherIsEnabled bool
 	workerShutdownWG sync.WaitGroup
@@ -97,33 +93,15 @@ func newWorker(o workerOpt) (*worker, error) {
 func (worker *worker) startNewWorkerThread() {
 	workerShutdownWG.Add(1)
 	defer workerShutdownWG.Done()
-
-	backoff := minWorkerErrorBackoff
-	failureCount := 0
-	backingOffLock := sync.RWMutex{}
+	backoff := &exponentialBackoff{
+		maxBackoff:             1 * time.Second,
+		minBackoff:             100 * time.Millisecond,
+		maxConsecutiveFailures: 6,
+	}
 
 	for {
 		// if the worker can stay up longer than backoff*2, it is probably an application error
-		upFunc := sync.Once{}
-		go func() {
-			backingOffLock.RLock()
-			wait := backoff * 2
-			backingOffLock.RUnlock()
-			time.Sleep(wait)
-			upFunc.Do(func() {
-				backingOffLock.Lock()
-				defer backingOffLock.Unlock()
-				// if we come back to a stable state, reset the failure count
-				if backoff == minWorkerErrorBackoff {
-					failureCount = 0
-				}
-
-				// earn back the backoff over time
-				if failureCount > 0 {
-					backoff = max(backoff/2, 100*time.Millisecond)
-				}
-			})
-		}()
+		backoff.wait()
 
 		metrics.StartWorker(worker.fileName)
 
@@ -176,31 +154,17 @@ func (worker *worker) startNewWorkerThread() {
 				c.Write(zap.String("worker", worker.fileName))
 			}
 			metrics.StopWorker(worker.fileName, StopReasonRestart)
+			backoff.recordSuccess()
 			continue
 		}
 
 		// on exit status 1 we log the error and apply an exponential backoff when restarting
-		upFunc.Do(func() {
-			backingOffLock.Lock()
-			defer backingOffLock.Unlock()
-			// if we end up here, the worker has not been up for backoff*2
-			// this is probably due to a syntax error or another fatal error
-			if failureCount >= maxWorkerConsecutiveFailures {
-				if !watcherIsEnabled {
-					panic(fmt.Errorf("workers %q: too many consecutive failures", worker.fileName))
-				}
-				logger.Warn("many consecutive worker failures", zap.String("worker", worker.fileName), zap.Int("failures", failureCount))
+		if backoff.recordFailure() {
+			if !watcherIsEnabled {
+				panic(fmt.Errorf("workers %q: too many consecutive failures", worker.fileName))
 			}
-			failureCount += 1
-		})
-		backingOffLock.RLock()
-		wait := backoff
-		backingOffLock.RUnlock()
-		time.Sleep(wait)
-		backingOffLock.Lock()
-		backoff *= 2
-		backoff = min(backoff, maxWorkerErrorBackoff)
-		backingOffLock.Unlock()
+			logger.Warn("many consecutive worker failures", zap.String("worker", worker.fileName), zap.Int("failures", backoff.failureCount))
+		}
 		metrics.StopWorker(worker.fileName, StopReasonCrash)
 	}