feat: retry transient sync requests

docs/PLUGIN_RUNTIME.md

@@ -554,6 +554,8 @@ bundled runtime. Это реальный runtime contract для cooperative bun
 | `api.files.showInFolder(relativePath)` | ✅ Работает | Показывает vault file/folder в системном файловом менеджере, требует `files.openExternal` |
 | `api.workbench.openResource(request)` | ✅ Работает | Routes vault resources to `openProviders` |
 | `api.workbench.editResource(request)` | ✅ Работает | Same routing, forcing `mode: "edit"` |
+| `api.sync.now()` | ✅ Работает | Push/pull с bounded retry/backoff для transient HTTP/network failures |
+| `api.sync.status()` | ✅ Работает | Возвращает configured/connected/error/revoked state, lastError, unpushed count |
 | `api.dispose()` | ✅ Работает | Очищает command handlers и event subscriptions текущего API instance |
 
 Ограничения:

internal/core/sync/client.go

@@ -61,6 +61,10 @@ type Client struct {
 	HTTP        *http.Client
 }
 
+var syncRetrySleep = time.Sleep
+
+const syncHTTPAttempts = 3
+
 // NewClient creates a sync client.
 func NewClient(serverURL, apiKey, deviceID, vaultRoot string) *Client {
 	return &Client{
@@ -318,7 +322,11 @@ func (c *Client) post(path string, body, result interface{}) error {
 			return err
 		}
 	}
-	req, err := http.NewRequest("POST", c.ServerURL+path, &b)
+	payload := b.Bytes()
+
+	var lastErr error
+	for attempt := 1; attempt <= syncHTTPAttempts; attempt++ {
+		req, err := http.NewRequest("POST", c.ServerURL+path, bytes.NewReader(payload))
 		if err != nil {
 			return err
 		}
@@ -327,21 +335,39 @@ func (c *Client) post(path string, body, result interface{}) error {
 
 		resp, err := c.HTTP.Do(req)
 		if err != nil {
-		return fmt.Errorf("http: %w", err)
+			lastErr = fmt.Errorf("http: %w", err)
+			if attempt < syncHTTPAttempts {
+				syncRetrySleep(syncBackoffDelay(attempt))
+				continue
+			}
+			return lastErr
 		}
-	defer resp.Body.Close()
-
 		if resp.StatusCode >= 400 {
-		return c.readErrorBody(resp, resp.StatusCode)
+			if isTransientHTTPStatus(resp.StatusCode) && attempt < syncHTTPAttempts {
+				_, _ = io.Copy(io.Discard, resp.Body)
+				_ = resp.Body.Close()
+				syncRetrySleep(syncBackoffDelay(attempt))
+				continue
+			}
+			err := c.readErrorBody(resp, resp.StatusCode)
+			_ = resp.Body.Close()
+			return err
 		}
 
 		if result != nil {
-		return json.NewDecoder(resp.Body).Decode(result)
+			err := json.NewDecoder(resp.Body).Decode(result)
+			_ = resp.Body.Close()
+			return err
 		}
+		_ = resp.Body.Close()
 		return nil
+	}
+	return lastErr
 }
 
 func (c *Client) get(path string, result interface{}) error {
+	var lastErr error
+	for attempt := 1; attempt <= syncHTTPAttempts; attempt++ {
 		req, err := http.NewRequest("GET", c.ServerURL+path, nil)
 		if err != nil {
 			return err
@@ -350,18 +376,48 @@ func (c *Client) get(path string, result interface{}) error {
 
 		resp, err := c.HTTP.Do(req)
 		if err != nil {
-		return fmt.Errorf("http: %w", err)
+			lastErr = fmt.Errorf("http: %w", err)
+			if attempt < syncHTTPAttempts {
+				syncRetrySleep(syncBackoffDelay(attempt))
+				continue
+			}
+			return lastErr
 		}
-	defer resp.Body.Close()
-
 		if resp.StatusCode >= 400 {
-		return c.readErrorBody(resp, resp.StatusCode)
+			if isTransientHTTPStatus(resp.StatusCode) && attempt < syncHTTPAttempts {
+				_, _ = io.Copy(io.Discard, resp.Body)
+				_ = resp.Body.Close()
+				syncRetrySleep(syncBackoffDelay(attempt))
+				continue
+			}
+			err := c.readErrorBody(resp, resp.StatusCode)
+			_ = resp.Body.Close()
+			return err
 		}
 
 		if result != nil {
-		return json.NewDecoder(resp.Body).Decode(result)
+			err := json.NewDecoder(resp.Body).Decode(result)
+			_ = resp.Body.Close()
+			return err
 		}
+		_ = resp.Body.Close()
 		return nil
+	}
+	return lastErr
+}
+
+func syncBackoffDelay(attempt int) time.Duration {
+	return time.Duration(attempt) * 250 * time.Millisecond
+}
+
+func isTransientHTTPStatus(statusCode int) bool {
+	switch statusCode {
+	case http.StatusRequestTimeout, http.StatusTooManyRequests, http.StatusInternalServerError,
+		http.StatusBadGateway, http.StatusServiceUnavailable, http.StatusGatewayTimeout:
+		return true
+	default:
+		return false
+	}
 }
 
 func (c *Client) readErrorBody(resp *http.Response, statusCode int) error {

internal/core/sync/client_test.go

@@ -0,0 +1,88 @@
+package sync
+
+import (
+	"encoding/json"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+	"time"
+)
+
+func withoutSyncRetrySleep(t *testing.T) {
+	t.Helper()
+	original := syncRetrySleep
+	syncRetrySleep = func(time.Duration) {}
+	t.Cleanup(func() {
+		syncRetrySleep = original
+	})
+}
+
+func TestPushRetriesTransientServerErrors(t *testing.T) {
+	withoutSyncRetrySleep(t)
+
+	attempts := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		if r.URL.Path != "/api/v1/sync/push" {
+			http.NotFound(w, r)
+			return
+		}
+		attempts++
+		if attempts < 3 {
+			http.Error(w, "try again", http.StatusServiceUnavailable)
+			return
+		}
+		w.Header().Set("Content-Type", "application/json")
+		_ = json.NewEncoder(w).Encode(map[string]interface{}{
+			"accepted":  []string{"op-1"},
+			"count":     1,
+			"conflicts": []map[string]interface{}{},
+		})
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "", "device-1", t.TempDir())
+	client.DeviceToken = "token"
+	result, err := client.Push([]Op{{
+		OpID:       "op-1",
+		EntityType: EntityFile,
+		EntityID:   "Docs/one.txt",
+		OpType:     OpCreate,
+		CreatedAt:  time.Now().UTC().Format(time.RFC3339),
+	}})
+	if err != nil {
+		t.Fatalf("Push: %v", err)
+	}
+	if attempts != 3 {
+		t.Fatalf("attempts = %d, want 3", attempts)
+	}
+	if len(result.Accepted) != 1 || result.Accepted[0] != "op-1" {
+		t.Fatalf("push result = %#v", result)
+	}
+}
+
+func TestPushDoesNotRetryClientErrors(t *testing.T) {
+	withoutSyncRetrySleep(t)
+
+	attempts := 0
+	server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+		attempts++
+		http.Error(w, "unauthorized", http.StatusUnauthorized)
+	}))
+	defer server.Close()
+
+	client := NewClient(server.URL, "", "device-1", t.TempDir())
+	client.DeviceToken = "token"
+	_, err := client.Push([]Op{{
+		OpID:       "op-1",
+		EntityType: EntityFile,
+		EntityID:   "Docs/one.txt",
+		OpType:     OpCreate,
+		CreatedAt:  time.Now().UTC().Format(time.RFC3339),
+	}})
+	if err == nil {
+		t.Fatal("Push should fail on unauthorized response")
+	}
+	if attempts != 1 {
+		t.Fatalf("attempts = %d, want 1", attempts)
+	}
+}