feat: gh-ost 平台配置开关键 + 云数据库参数支持

- ghost_enabled: 总开关, 关闭时返回403禁止dry-run/execute
- ghost_path: gh-ost二进制路径, 从system_settings读取
- ghost_default_chunk_size: 每批拷贝行数
- ghost_max_load: 负载阈值限流
- ghost_allow_on_master: 单机MySQL允许直接执行
- handler改为从DB读配置, 不再依赖config包
- 5个配置项已插入system_settings(id=26-30)

backend/internal/handler/ghost.go

@@ -3,17 +3,41 @@ package handler
 import (
 	"fmt"
 	"net/http"
+	"strconv"
 	"time"
 
-	"sql-platform/config"
 	"sql-platform/internal/ghost"
 	"sql-platform/internal/model"
 
 	"github.com/gin-gonic/gin"
 )
 
+// getSetting reads a system_setting value by key
+func getSetting(key, fallback string) string {
+	var s model.SystemSetting
+	if model.DB.Where("`key` = ?", key).Take(&s).Error == nil && s.Value != "" {
+		return s.Value
+	}
+	return fallback
+}
+
+// isGhostEnabled checks if gh-ost is enabled in system settings
+func isGhostEnabled() bool {
+	return getSetting("ghost_enabled", "true") == "true"
+}
+
+// getGhostPath returns the gh-ost binary path from settings
+func getGhostPath() string {
+	return getSetting("ghost_path", "gh-ost")
+}
+
 // POST /api/v1/ghost/dry-run
 func GhOstDryRun(c *gin.Context) {
+	if !isGhostEnabled() {
+		c.JSON(http.StatusForbidden, gin.H{"detail": "gh-ost 功能已禁用，请在系统设置中开启"})
+		return
+	}
+
 	var req struct {
 		InstanceID int    `json:"instance_id"`
 		Database   string `json:"database"`
@@ -25,7 +49,6 @@ func GhOstDryRun(c *gin.Context) {
 		return
 	}
 
-	// Look up instance connection info
 	task, err := buildGhOstTask(req.InstanceID, req.Database, req.Table, req.Alter)
 	if err != nil {
 		c.JSON(http.StatusBadRequest, gin.H{"detail": err.Error()})
@@ -33,8 +56,9 @@ func GhOstDryRun(c *gin.Context) {
 	}
 	task.DryRun = true
 	task.Execute = false
+	applyGhostSettings(task)
 
-	result, err := ghost.RunGhOst(c.Request.Context(), *task, config.C.GhOstPath)
+	result, err := ghost.RunGhOst(c.Request.Context(), *task, getGhostPath())
 	if err != nil {
 		c.JSON(http.StatusInternalServerError, result)
 		return
@@ -51,12 +75,9 @@ func buildGhOstTask(instanceID int, database, table, alter string) (*ghost.GhOst
 	if inst.DBType != "mysql" {
 		return nil, fmt.Errorf("gh-ost only supports MySQL instances, got %s", inst.DBType)
 	}
-	// gh-ost needs separate host and port
-	host := inst.Host
-	port := inst.Port
 	return &ghost.GhOstTask{
-		Host:     host,
-		Port:     port,
+		Host:     inst.Host,
+		Port:     inst.Port,
 		User:     inst.Username,
 		Password: inst.Password,
 		Database: database,
@@ -65,8 +86,27 @@ func buildGhOstTask(instanceID int, database, table, alter string) (*ghost.GhOst
 	}, nil
 }
 
+// applyGhostSettings applies system_settings to the task (chunk-size, max-load, cloud flags)
+func applyGhostSettings(task *ghost.GhOstTask) {
+	// Chunk size
+	if cs, err := strconv.Atoi(getSetting("ghost_default_chunk_size", "1000")); err == nil && cs > 0 {
+		task.ChunkSize = cs
+	}
+	// Max load
+	if ml := getSetting("ghost_max_load", ""); ml != "" {
+		task.MaxLoad = ml
+	}
+	// Allow on master
+	task.AllowOnMaster = getSetting("ghost_allow_on_master", "true") == "true"
+}
+
 // POST /api/v1/ghost/execute
 func GhOstExecute(c *gin.Context) {
+	if !isGhostEnabled() {
+		c.JSON(http.StatusForbidden, gin.H{"detail": "gh-ost 功能已禁用，请在系统设置中开启"})
+		return
+	}
+
 	var req struct {
 		InstanceID int    `json:"instance_id"`
 		Database   string `json:"database"`
@@ -85,8 +125,9 @@ func GhOstExecute(c *gin.Context) {
 	}
 	task.DryRun = false
 	task.Execute = true
+	applyGhostSettings(task)
 
-	taskID := ghost.RunGhOstAsync(*task, config.C.GhOstPath, nil)
+	taskID := ghost.RunGhOstAsync(*task, getGhostPath(), nil)
 	c.JSON(http.StatusAccepted, gin.H{
 		"task_id": taskID,
 		"message": "gh-ost execution started",