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# DataSource Layer Implementation
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# DataSource 接入说明
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## Overview
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本文档说明当前 `sync_state_machine.datasource` 层的职责边界,以及新增 datasource / handler 时应如何接入。
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This document describes the new datasource layer for `sync_system_new`, which is completely decoupled from the sync strategy and state machine logic.
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如需看完整库化接入方式,优先参考 [docs/library_integration_guide.md](../../docs/library_integration_guide.md)。
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## Architecture
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## 1. 分层模型
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The datasource layer follows a pure execution model:
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当前 datasource 层分为两部分:
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1. **Load**: Reads data from backend and creates `SyncNode` instances
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2. **Save**: Executes actions (CREATE/UPDATE/DELETE) based on `node.action`
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3. **Update Status**: Sets `node.status` to SUCCESS or FAILED after execution
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1. `DataSource`
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- 管理 handler 注册
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- 管理 collection 注入
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- 负责按 `node_type` 组织 `load_all()` / `sync_all()`
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- 汇总并回写 `TaskResult`
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### Key Principles
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2. `Handler`
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- 负责某一个 `node_type` 的具体 I/O
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- 负责把原始数据转成 `SyncNode`
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- 负责执行 create / update / delete / poll
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- **No Strategy Logic**: Datasource doesn't make decisions about what to sync
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- **State-Driven**: Only reads `node.action` and `node.status` to determine behavior
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- **No ID Resolution**: IDs are already resolved by the strategy layer
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- **Backend Agnostic**: Abstract base class supports multiple backends
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设计原则:
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## Components
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- datasource 不承载业务策略
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- strategy 不直接做底层 I/O
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- 节点类型差异下沉到 handler
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### 1. Base Protocol (`base.py`)
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---
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#### `DataSourceProtocol`
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## 2. 当前可直接复用的 datasource
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Protocol defining the interface for all datasource implementations:
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### 2.1 JSONL
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- `JsonlDataSource`
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- `BaseJsonlHandler`
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适合:
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- fixture
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- 本地回放
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- 离线调试
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### 2.2 API
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- `ApiDataSource`
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- `ApiClient`
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- `BaseApiHandler`
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适合:
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- HTTP 推送
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- 异步任务轮询
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- 远端系统对接
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---
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## 3. 最推荐的扩展方式:只新增 handler
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多数情况下,不需要新增新的 datasource 类。
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推荐做法:
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1. 复用现有 `JsonlDataSource` 或 `ApiDataSource`
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2. 为你的 `node_type` 新增 handler
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3. 在 handler 中完成字段映射、加载、写入和轮询
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4. 将 handler 注册到 `DomainRegistry`
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这样可以保持:
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- pipeline 不变
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- datasource 生命周期不变
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- 策略层不感知底层来源
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---
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## 4. handler 需要实现什么
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### 4.1 JSONL handler
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通常继承 `BaseJsonlHandler`:
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```python
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async def load_nodes(
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node_type: str,
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collection: DataCollection,
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**filters: Any
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) -> None:
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"""Load data from backend and create SyncNodes"""
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async def save_nodes(
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node_type: str,
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collection: DataCollection
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) -> None:
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"""Execute pending actions for nodes"""
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class DemoJsonlHandler(BaseJsonlHandler):
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def __init__(self, datasource):
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super().__init__(
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datasource=datasource,
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node_type="demo",
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node_class=DemoSyncNode,
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schema=DemoSchema,
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)
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```
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#### `BaseDataSource`
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### 4.2 API handler
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Abstract base class providing common functionality:
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通常继承 `BaseApiHandler`,实现:
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- `load_nodes`: Creates SyncNodes from raw data
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- `save_nodes`: Executes actions and updates status
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- `_handle_create/update/delete`: Action-specific handlers
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- `load()`
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- `create_all()`
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- `update_all()`
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- `delete_all()`
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- `poll_tasks()`
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Subclasses implement:
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- `_load_raw_data`: Load from backend
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- `_create_item`: Execute CREATE
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- `_update_item`: Execute UPDATE
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- `_delete_item`: Execute DELETE
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- `_generate_id`: Generate new IDs
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并按需要补充:
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### 2. JSONL Implementation (`jsonl_datasource.py`)
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- `extract_created_id()`
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- `get_update_fields()`
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- 依赖节点 context 读取逻辑
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#### `JsonlDataSource`
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---
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JSONL-based datasource for local testing:
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## 5. 什么时候新增 DataSource 类
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**Features:**
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- Loads `.jsonl` files into memory
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- Generates UUIDs for new items
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- Supports filtering during load
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- Supports read-only mode
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- Persists changes back to files
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只有在现有 JSONL / API 模型都不匹配时,才建议新增 `BaseDataSource` 子类。
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**File Structure:**
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```
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data/
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├── contract_1.jsonl
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├── project_1.jsonl
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└── ...
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```
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例如:
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**Usage:**
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```python
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datasource = JsonlDataSource(Path("data/"))
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- 数据来自数据库快照
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- 数据来自 MQ / Kafka
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- 数据来自特殊 RPC 或 SDK
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# Load nodes
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await datasource.load_nodes("contract", collection, project_id="P1")
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即便新增 datasource,也建议保留同样的职责边界:
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# Execute actions
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await datasource.save_nodes("contract", collection)
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- datasource 负责调度
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- handler 负责节点类型差异
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# Persist to disk
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await datasource.save_all()
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```
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---
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### 3. Domain Handlers
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## 6. 注册方式
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Domain-specific handlers provide business logic (optional):
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**Example: `domain/contract/jsonl_handler.py`**
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接入新 `node_type` 时,最终仍通过 `DomainRegistry` 暴露给 pipeline:
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```python
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class ContractJsonlHandler:
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@staticmethod
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def validate_create(data: Any) -> None:
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"""Validate before create"""
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@staticmethod
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def transform_for_create(data: Any) -> Dict[str, Any]:
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"""Transform data before create"""
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DomainRegistry.register(
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node_type="demo",
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schema=DemoSchema,
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node_class=DemoSyncNode,
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strategy_class=DemoStrategy,
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jsonl_handler_class=DemoJsonlHandler,
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api_handler_class=DemoApiHandler,
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)
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```
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## Node Lifecycle
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---
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### Loading Phase
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## 7. 推荐阅读顺序
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1. Datasource reads raw data from backend
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2. Creates `SyncNode` for each item:
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- `node_id`: Unique session ID (e.g., "contract_C1")
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- `data_id`: Backend ID (e.g., "C1")
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- `origin_data`: Raw data from backend
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- `data`: Copy of origin_data (may be modified by strategy)
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- `action`: NONE (initial)
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- `status`: PENDING (initial)
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1. [docs/library_integration_guide.md](../../docs/library_integration_guide.md)
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2. `sync_state_machine/datasource/handler.py`
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3. `sync_state_machine/datasource/api/handler.py`
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4. `sync_state_machine/datasource/jsonl/handler.py`
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5. `sync_state_machine/pipeline/factory.py`
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### Execution Phase
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---
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For each node with `status == PENDING` and `action != NONE`:
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## 8. 结论
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1. **CREATE**:
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- Generate new ID via `_generate_id`
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- Call `_create_item` with new ID and data
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- Set `node.data_id` to new ID
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- Set `node.status` to SUCCESS
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如果你在接入新系统,优先判断:
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2. **UPDATE**:
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- Call `_update_item` with existing `data_id` and data
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- Set `node.status` to SUCCESS
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- 是否可以直接复用 `JsonlDataSource` / `ApiDataSource`
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- 是否只需要新增 handler
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- 是否需要在业务系统侧做 mapper / adapter
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3. **DELETE**:
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- Call `_delete_item` with `data_id`
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- Set `node.status` to SUCCESS
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4. **Error Handling**:
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- On exception: Set `node.status` to FAILED
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- Set `node.error` to exception message
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## Integration with Sync System
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The datasource is used by the pipeline layer:
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```python
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# 1. Load data
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local_ds = JsonlDataSource(Path("local_data/"))
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remote_ds = JsonlDataSource(Path("remote_data/"))
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local_collection = DataCollection("local")
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remote_collection = DataCollection("remote")
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await local_ds.load_nodes("contract", local_collection)
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await remote_ds.load_nodes("contract", remote_collection)
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# 2. Strategy layer determines actions
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strategy = ContractSyncStrategy(...)
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await strategy.bind(...) # Sets node.action
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# 3. Execute actions
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await remote_ds.save_nodes("contract", remote_collection)
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await remote_ds.save_all()
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```
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## Testing
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Comprehensive test suite in `tests/test_datasource.py`:
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- Basic loading and node creation
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- Filtering during load
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- CREATE/UPDATE/DELETE actions
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- Error handling and status updates
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- Read-only mode
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- Multiple node types
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Run tests:
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```bash
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python -m pytest sync_system_new/tests/test_datasource.py -v
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```
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## Future Extensions
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### API DataSource
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For production use, implement `ApiDataSource`:
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```python
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class ApiDataSource(BaseDataSource):
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async def _load_raw_data(self, node_type: str, **filters):
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# Call REST API
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async def _create_item(self, node_type: str, item_id: str, data):
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# POST request
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async def _generate_id(self, node_type: str, data):
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# Return None - server generates ID
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```
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### Database DataSource
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For SQL databases:
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```python
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class DatabaseDataSource(BaseDataSource):
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async def _load_raw_data(self, node_type: str, **filters):
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# SELECT query
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async def _create_item(self, node_type: str, item_id: str, data):
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# INSERT query
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```
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## Comparison with Legacy System
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### Legacy System (`sync_system/datasource/`)
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- Tightly coupled with RepositoryProtocol
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- Mixed concerns (data access + business logic)
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- Schema validation in datasource layer
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- Different interface for each entity type
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### New System (`sync_system_new/datasource/`)
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- Decoupled from strategy and state machine
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- Pure data access (business logic in domain handlers)
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- Generic interface for all entity types
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- Direct integration with SyncNode and DataCollection
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## Key Differences
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| Aspect | Legacy | New |
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|--------|--------|-----|
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| Coupling | Tight with sync policies | Decoupled from sync logic |
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| Interface | Repository per entity | Generic load/save |
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| ID Handling | Mixed responsibilities | IDs already resolved |
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| State Management | Mixed with data access | SyncNode-based |
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| Testing | Complex setup | Simple, focused tests |
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## Conclusion
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The new datasource layer provides:
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1. **Clear Separation**: Data access is isolated from sync logic
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2. **Flexibility**: Easy to add new backend types
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3. **Testability**: Simple, focused tests
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4. **Type Safety**: Full integration with Pydantic models
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5. **Maintainability**: Single responsibility per component
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通常情况下,**先写 handler,而不是先写新的 datasource**。
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