feat(base): 添加单任务内文件传输并发功能

- 引入 ThreadPoolExecutor 实现并行下载和上传
- 新增 download_files_parallel 和 upload_files_parallel 方法
- 添加任务传输并发数配置选项 TASK_DOWNLOAD_CONCURRENCY 和 TASK_UPLOAD_CONCURRENCY
- 实现并发数配置的环境变量解析和验证逻辑
- 在多个处理器中应用并行下载优化文件获取性能
- 更新 .env.example 配置文件模板
- 移除 FFmpeg 命令日志长度限制

handlers/compose_transition.py

@@ -91,23 +91,37 @@ class ComposeTransitionHandler(BaseHandler):
                 f"overlap_tail={overlap_tail_ms}ms, overlap_head={overlap_head_ms}ms"
             )
 
-            # 1. 下载前一个片段视频
+            # 1. 并行下载前后片段视频
             prev_video_file = os.path.join(work_dir, 'prev_segment.mp4')
-            if not self.download_file(prev_segment['videoUrl'], prev_video_file):
+            next_video_file = os.path.join(work_dir, 'next_segment.mp4')
+            download_results = self.download_files_parallel([
+                {
+                    'key': 'prev_video',
+                    'url': prev_segment['videoUrl'],
+                    'dest': prev_video_file,
+                    'required': True
+                },
+                {
+                    'key': 'next_video',
+                    'url': next_segment['videoUrl'],
+                    'dest': next_video_file,
+                    'required': True
+                }
+            ])
+            prev_result = download_results.get('prev_video')
+            if not prev_result or not prev_result['success']:
                 return TaskResult.fail(
                     ErrorCode.E_INPUT_UNAVAILABLE,
                     f"Failed to download prev segment video: {prev_segment['videoUrl']}"
                 )
-
-            # 2. 下载后一个片段视频
-            next_video_file = os.path.join(work_dir, 'next_segment.mp4')
-            if not self.download_file(next_segment['videoUrl'], next_video_file):
+            next_result = download_results.get('next_video')
+            if not next_result or not next_result['success']:
                 return TaskResult.fail(
                     ErrorCode.E_INPUT_UNAVAILABLE,
                     f"Failed to download next segment video: {next_segment['videoUrl']}"
                 )
 
-            # 3. 获取前一个片段的实际时长
+            # 2. 获取前一个片段的实际时长
             prev_duration = self.probe_duration(prev_video_file)
             if not prev_duration:
                 return TaskResult.fail(
@@ -115,7 +129,7 @@ class ComposeTransitionHandler(BaseHandler):
                     "Failed to probe prev segment duration"
                 )
 
-            # 4. 构建转场合成命令
+            # 3. 构建转场合成命令
             output_file = os.path.join(work_dir, 'transition.mp4')
             cmd = self._build_command(
                 prev_video_file=prev_video_file,
@@ -128,25 +142,25 @@ class ComposeTransitionHandler(BaseHandler):
                 output_spec=output_spec
             )
 
-            # 5. 执行 FFmpeg
+            # 4. 执行 FFmpeg
             if not self.run_ffmpeg(cmd, task.task_id):
                 return TaskResult.fail(
                     ErrorCode.E_FFMPEG_FAILED,
                     "FFmpeg transition composition failed"
                 )
 
-            # 6. 验证输出文件
+            # 5. 验证输出文件
             if not self.ensure_file_exists(output_file, min_size=1024):
                 return TaskResult.fail(
                     ErrorCode.E_FFMPEG_FAILED,
                     "Transition output file is missing or too small"
                 )
 
-            # 7. 获取实际时长
+            # 6. 获取实际时长
             actual_duration = self.probe_duration(output_file)
             actual_duration_ms = int(actual_duration * 1000) if actual_duration else transition_duration_ms
 
-            # 8. 上传产物
+            # 7. 上传产物
             transition_video_url = self.upload_file(task.task_id, 'video', output_file)
             if not transition_video_url:
                 return TaskResult.fail(