feat: make desktop FFI invocation asynchronous

bind/desktop/invoke_executor.go

@@ -0,0 +1,123 @@
+package main
+
+import (
+	"fmt"
+	"runtime"
+	"sync"
+)
+
+const (
+	minInvokeConcurrency = 4
+	maxInvokeConcurrency = 32
+)
+
+type invokeRequest struct {
+	method string
+	path   string
+	query  string
+	body   string
+}
+
+type invokeTask struct {
+	request  invokeRequest
+	complete func(result string, err error)
+}
+
+// invokeExecutor keeps native API work concurrent without ever rejecting a
+// request because all workers are busy. submit only appends to the waiting
+// queue; callers observe backpressure through the Future completed by the
+// callback rather than by blocking the FFI entry point.
+type invokeExecutor struct {
+	mu      sync.Mutex
+	ready   *sync.Cond
+	queue   []invokeTask
+	closed  bool
+	workers sync.WaitGroup
+	handler func(invokeRequest) string
+}
+
+func invokeConcurrency(cpuCount int) int {
+	concurrency := cpuCount * 2
+	if concurrency < minInvokeConcurrency {
+		return minInvokeConcurrency
+	}
+	if concurrency > maxInvokeConcurrency {
+		return maxInvokeConcurrency
+	}
+	return concurrency
+}
+
+func newInvokeExecutor(workerCount int, handler func(invokeRequest) string) *invokeExecutor {
+	if workerCount < 1 {
+		workerCount = 1
+	}
+	executor := &invokeExecutor{handler: handler}
+	executor.ready = sync.NewCond(&executor.mu)
+	executor.workers.Add(workerCount)
+	for range workerCount {
+		go executor.run()
+	}
+	return executor
+}
+
+func newDefaultInvokeExecutor(handler func(invokeRequest) string) *invokeExecutor {
+	return newInvokeExecutor(invokeConcurrency(runtime.GOMAXPROCS(0)), handler)
+}
+
+func (e *invokeExecutor) submit(task invokeTask) bool {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	if e.closed {
+		return false
+	}
+	e.queue = append(e.queue, task)
+	e.ready.Signal()
+	return true
+}
+
+func (e *invokeExecutor) close() {
+	e.mu.Lock()
+	e.closed = true
+	e.ready.Broadcast()
+	e.mu.Unlock()
+	e.workers.Wait()
+}
+
+func (e *invokeExecutor) run() {
+	defer e.workers.Done()
+	for {
+		task, ok := e.take()
+		if !ok {
+			return
+		}
+		result, err := e.execute(task.request)
+		task.complete(result, err)
+	}
+}
+
+func (e *invokeExecutor) take() (invokeTask, bool) {
+	e.mu.Lock()
+	defer e.mu.Unlock()
+	for len(e.queue) == 0 && !e.closed {
+		e.ready.Wait()
+	}
+	if len(e.queue) == 0 {
+		return invokeTask{}, false
+	}
+	task := e.queue[0]
+	e.queue[0] = invokeTask{}
+	e.queue = e.queue[1:]
+	if len(e.queue) == 0 {
+		e.queue = nil
+	}
+	return task, true
+}
+
+func (e *invokeExecutor) execute(request invokeRequest) (result string, err error) {
+	defer func() {
+		if recovered := recover(); recovered != nil {
+			err = fmt.Errorf("invoke panic: %v", recovered)
+		}
+	}()
+	return e.handler(request), nil
+}

bind/desktop/invoke_executor_test.go

@@ -0,0 +1,102 @@
+package main
+
+import (
+	"strconv"
+	"sync"
+	"sync/atomic"
+	"testing"
+	"time"
+)
+
+func TestInvokeConcurrency(t *testing.T) {
+	tests := []struct {
+		cpus int
+		want int
+	}{
+		{cpus: 1, want: 4},
+		{cpus: 2, want: 4},
+		{cpus: 4, want: 8},
+		{cpus: 8, want: 16},
+		{cpus: 16, want: 32},
+		{cpus: 64, want: 32},
+	}
+	for _, test := range tests {
+		t.Run(strconv.Itoa(test.cpus), func(t *testing.T) {
+			if got := invokeConcurrency(test.cpus); got != test.want {
+				t.Fatalf("invokeConcurrency(%d) = %d, want %d", test.cpus, got, test.want)
+			}
+		})
+	}
+}
+
+func TestInvokeExecutorWaitsWithoutRejecting(t *testing.T) {
+	const (
+		workerCount = 2
+		taskCount   = 6
+	)
+	release := make(chan struct{})
+	started := make(chan struct{}, taskCount)
+	var active atomic.Int32
+	var maxActive atomic.Int32
+	executor := newInvokeExecutor(workerCount, func(request invokeRequest) string {
+		current := active.Add(1)
+		for {
+			maximum := maxActive.Load()
+			if current <= maximum || maxActive.CompareAndSwap(maximum, current) {
+				break
+			}
+		}
+		started <- struct{}{}
+		<-release
+		active.Add(-1)
+		return request.path
+	})
+
+	var completed sync.WaitGroup
+	completed.Add(taskCount)
+	for i := range taskCount {
+		accepted := executor.submit(invokeTask{
+			request: invokeRequest{path: strconv.Itoa(i)},
+			complete: func(string, error) {
+				completed.Done()
+			},
+		})
+		if !accepted {
+			t.Fatalf("task %d was rejected while all workers were busy", i)
+		}
+	}
+
+	for range workerCount {
+		select {
+		case <-started:
+		case <-time.After(time.Second):
+			t.Fatal("workers did not start queued tasks")
+		}
+	}
+	if got := maxActive.Load(); got != workerCount {
+		t.Fatalf("maximum active tasks = %d, want %d", got, workerCount)
+	}
+
+	close(release)
+	completed.Wait()
+	executor.close()
+}
+
+func TestInvokeExecutorConvertsPanicsToErrors(t *testing.T) {
+	executor := newInvokeExecutor(1, func(invokeRequest) string {
+		panic("boom")
+	})
+	completed := make(chan error, 1)
+	executor.submit(invokeTask{complete: func(_ string, err error) {
+		completed <- err
+	}})
+	select {
+	case err := <-completed:
+		if err == nil || err.Error() != "invoke panic: boom" {
+			t.Fatalf("unexpected error: %v", err)
+		}
+	case <-time.After(time.Second):
+		t.Fatal("panic result was not completed")
+	}
+	executor.close()
+}

bind/desktop/main.go

@@ -6,14 +6,21 @@ package main
 
 typedef void (*TaskEventCallback)(char* payload);
 
+typedef void (*InvokeResultCallback)(uint64_t request_id, int success, char* payload);
+
 static void callTaskEventCallback(uintptr_t callback, char* payload) {
 	((TaskEventCallback)callback)(payload);
 }
+
+static void callInvokeResultCallback(uintptr_t callback, uint64_t request_id, int success, char* payload) {
+	((InvokeResultCallback)callback)(request_id, success, payload);
+}
 */
 import "C"
 import (
 	"encoding/json"
 	"fmt"
+	"sync"
 	"unsafe"
 
 	"github.com/GopeedLab/gopeed/pkg/rest"
@@ -22,6 +29,20 @@ import (
 
 func main() {}
 
+var (
+	invokeExecutorOnce sync.Once
+	desktopInvoker     *invokeExecutor
+)
+
+func getInvokeExecutor() *invokeExecutor {
+	invokeExecutorOnce.Do(func() {
+		desktopInvoker = newDefaultInvokeExecutor(func(request invokeRequest) string {
+			return rest.Invoke(request.method, request.path, request.query, request.body)
+		})
+	})
+	return desktopInvoker
+}
+
 //export Start
 func Start(cfg *C.char) (int, *C.char) {
 	var config model.StartConfig
@@ -85,6 +106,43 @@ func Invoke(method *C.char, path *C.char, query *C.char, body *C.char) *C.char {
 	))
 }
 
+//export InvokeAsync
+func InvokeAsync(
+	method *C.char,
+	path *C.char,
+	query *C.char,
+	body *C.char,
+	requestID C.ulonglong,
+	callback C.uintptr_t,
+) {
+	if callback == 0 {
+		return
+	}
+	request := invokeRequest{
+		method: C.GoString(method),
+		path:   C.GoString(path),
+		query:  C.GoString(query),
+		body:   C.GoString(body),
+	}
+	complete := func(result string, err error) {
+		success := C.int(1)
+		payload := result
+		if err != nil {
+			success = 0
+			payload = err.Error()
+		}
+		C.callInvokeResultCallback(
+			callback,
+			C.uint64_t(requestID),
+			success,
+			C.CString(payload),
+		)
+	}
+	if !getInvokeExecutor().submit(invokeTask{request: request, complete: complete}) {
+		complete("", fmt.Errorf("invoke executor is closed"))
+	}
+}
+
 //export SubscribeTaskEvents
 func SubscribeTaskEvents(mask C.ulonglong, callback C.uintptr_t) {
 	if mask == 0 || callback == 0 {