trustgraph/docs/tech-specs/import-export-graceful-shutdown.zh-cn.md

layout	title	parent
default	导入/导出 优雅关闭 技术规范	Chinese (Beta)

导入/导出 优雅关闭 技术规范

Beta Translation: This document was translated via Machine Learning and as such may not be 100% accurate. All non-English languages are currently classified as Beta.

问题陈述

<<<<<<< HEAD TrustGraph 网关在导入和导出操作中，在 WebSocket 连接关闭时，目前存在消息丢失的问题。 这是由于存在竞争条件，导致正在传输的消息在到达目的地之前被丢弃（对于导入，是丢弃到 Pulsar 队列的消息；对于导出，是丢弃到 WebSocket 客户端的消息）。

导入端问题

1. 发布者的 asyncio.Queue 缓冲区在关闭时未被清空
2. 在确保所有排队的消息到达 Pulsar 之前，WebSocket 连接关闭 ======= TrustGraph 网关在导入和导出操作的 WebSocket 关闭过程中，目前存在消息丢失的问题。 这是由于存在竞争条件，导致正在传输的消息在到达目的地之前被丢弃（对于导入，是丢弃到 Pulsar 队列的消息；对于导出，是丢弃到 WebSocket 客户端的消息）。

导入端问题

1. 发布者的 asyncio.Queue 缓冲区在关闭时未被清空
2. 在确保所有排队的消息到达 Pulsar 之前，WebSocket 被关闭

82edf2d (New md files from RunPod)

3. 没有用于确认消息成功传递的机制

导出端问题

1. 消息在成功传递到客户端之前，已在 Pulsar 中得到确认
2. 预定义的超时时间会导致队列已满时消息丢失
3. 没有用于处理慢速消费者的反压机制
4. 存在多个缓冲区，数据可能在此处丢失

架构概述

Import Flow:
Client -> Websocket -> TriplesImport -> Publisher -> Pulsar Queue

Export Flow:
Pulsar Queue -> Subscriber -> TriplesExport -> Websocket -> Client

建议的修复方案

1. 发布者改进（导入端）

A. 优雅的队列清空

文件: trustgraph-base/trustgraph/base/publisher.py

class Publisher:
    def __init__(self, client, topic, schema=None, max_size=10,
                 chunking_enabled=True, drain_timeout=5.0):
        self.client = client
        self.topic = topic
        self.schema = schema
        self.q = asyncio.Queue(maxsize=max_size)
        self.chunking_enabled = chunking_enabled
        self.running = True
        self.draining = False  # New state for graceful shutdown
        self.task = None
        self.drain_timeout = drain_timeout

    async def stop(self):
        """Initiate graceful shutdown with draining"""
        self.running = False
        self.draining = True
        
        if self.task:
            # Wait for run() to complete draining
            await self.task

    async def run(self):
        """Enhanced run method with integrated draining logic"""
        while self.running or self.draining:
            try:
                producer = self.client.create_producer(
                    topic=self.topic,
                    schema=JsonSchema(self.schema),
                    chunking_enabled=self.chunking_enabled,
                )

                drain_end_time = None
                
                while self.running or self.draining:
                    try:
                        # Start drain timeout when entering drain mode
                        if self.draining and drain_end_time is None:
                            drain_end_time = time.time() + self.drain_timeout
                            logger.info(f"Publisher entering drain mode, timeout={self.drain_timeout}s")
                        
                        # Check drain timeout
                        if self.draining and time.time() > drain_end_time:
                            if not self.q.empty():
                                logger.warning(f"Drain timeout reached with {self.q.qsize()} messages remaining")
                            self.draining = False
                            break
                        
                        # Calculate wait timeout based on mode
                        if self.draining:
                            # Shorter timeout during draining to exit quickly when empty
                            timeout = min(0.1, drain_end_time - time.time())
                        else:
                            # Normal operation timeout
                            timeout = 0.25
                        
                        # Get message from queue
                        id, item = await asyncio.wait_for(
                            self.q.get(),
                            timeout=timeout
                        )
                        
                        # Send the message (single place for sending)
                        if id:
                            producer.send(item, { "id": id })
                        else:
                            producer.send(item)
                            
                    except asyncio.TimeoutError:
                        # If draining and queue is empty, we're done
                        if self.draining and self.q.empty():
                            logger.info("Publisher queue drained successfully")
                            self.draining = False
                            break
                        continue
                        
                    except asyncio.QueueEmpty:
                        # If draining and queue is empty, we're done  
                        if self.draining and self.q.empty():
                            logger.info("Publisher queue drained successfully")
                            self.draining = False
                            break
                        continue
                
                # Flush producer before closing
                if producer:
                    producer.flush()
                    producer.close()

            except Exception as e:
                logger.error(f"Exception in publisher: {e}", exc_info=True)

            if not self.running and not self.draining:
                return

            # If handler drops out, sleep a retry
            await asyncio.sleep(1)

    async def send(self, id, item):
        """Send still works normally - just adds to queue"""
        if self.draining:
            # Optionally reject new messages during drain
            raise RuntimeError("Publisher is shutting down, not accepting new messages")
        await self.q.put((id, item))

主要设计优势： 单一发送位置： 所有 producer.send() 调用都发生在 run() 方法内的单一位置。 清晰的状态机： 三个明确的状态 - 运行中、正在排空、已停止。 超时保护： 在排空过程中不会无限期挂起。 更好的可观察性： 清晰地记录排空进度和状态转换。 可选的消息拒绝： 可以在关闭阶段拒绝新的消息。

B. 改进的关闭顺序

文件： trustgraph-flow/trustgraph/gateway/dispatch/triples_import.py

class TriplesImport:
    async def destroy(self):
        """Enhanced destroy with proper shutdown order"""
        # Step 1: Stop accepting new messages
        self.running.stop()
        
        # Step 2: Wait for publisher to drain its queue
        logger.info("Draining publisher queue...")
        await self.publisher.stop()
        
        # Step 3: Close websocket only after queue is drained
        if self.ws:
            await self.ws.close()

2. 订阅者改进（导出端）

A. 集成排空模式

文件: trustgraph-base/trustgraph/base/subscriber.py

class Subscriber:
    def __init__(self, client, topic, subscription, consumer_name,
                 schema=None, max_size=100, metrics=None,
                 backpressure_strategy="block", drain_timeout=5.0):
        # ... existing init ...
        self.backpressure_strategy = backpressure_strategy
        self.running = True
        self.draining = False  # New state for graceful shutdown
        self.drain_timeout = drain_timeout
        self.pending_acks = {}  # Track messages awaiting delivery
        
    async def stop(self):
        """Initiate graceful shutdown with draining"""
        self.running = False
        self.draining = True
        
        if self.task:
            # Wait for run() to complete draining
            await self.task
            
    async def run(self):
        """Enhanced run method with integrated draining logic"""
        while self.running or self.draining:
            if self.metrics:
                self.metrics.state("stopped")

            try:
                self.consumer = self.client.subscribe(
                    topic = self.topic,
                    subscription_name = self.subscription,
                    consumer_name = self.consumer_name,
                    schema = JsonSchema(self.schema),
                )

                if self.metrics:
                    self.metrics.state("running")

                logger.info("Subscriber running...")
                drain_end_time = None

                while self.running or self.draining:
                    # Start drain timeout when entering drain mode
                    if self.draining and drain_end_time is None:
                        drain_end_time = time.time() + self.drain_timeout
                        logger.info(f"Subscriber entering drain mode, timeout={self.drain_timeout}s")
                        
                        # Stop accepting new messages from Pulsar during drain
                        self.consumer.pause_message_listener()
                    
                    # Check drain timeout
                    if self.draining and time.time() > drain_end_time:
                        async with self.lock:
                            total_pending = sum(
                                q.qsize() for q in 
                                list(self.q.values()) + list(self.full.values())
                            )
                            if total_pending > 0:
                                logger.warning(f"Drain timeout reached with {total_pending} messages in queues")
                        self.draining = False
                        break
                    
                    # Check if we can exit drain mode
                    if self.draining:
                        async with self.lock:
                            all_empty = all(
                                q.empty() for q in 
                                list(self.q.values()) + list(self.full.values())
                            )
                            if all_empty and len(self.pending_acks) == 0:
                                logger.info("Subscriber queues drained successfully")
                                self.draining = False
                                break
                    
                    # Process messages only if not draining
                    if not self.draining:
                        try:
                            msg = await asyncio.to_thread(
                                self.consumer.receive,
                                timeout_millis=250
                            )
                        except _pulsar.Timeout:
                            continue
                        except Exception as e:
                            logger.error(f"Exception in subscriber receive: {e}", exc_info=True)
                            raise e

                        if self.metrics:
                            self.metrics.received()

                        # Process the message
                        await self._process_message(msg)
                    else:
                        # During draining, just wait for queues to empty
                        await asyncio.sleep(0.1)

            except Exception as e:
                logger.error(f"Subscriber exception: {e}", exc_info=True)

            finally:
                # Negative acknowledge any pending messages
                for msg in self.pending_acks.values():
                    self.consumer.negative_acknowledge(msg)
                self.pending_acks.clear()

                if self.consumer:
                    self.consumer.unsubscribe()
                    self.consumer.close()
                    self.consumer = None

            if self.metrics:
                self.metrics.state("stopped")

            if not self.running and not self.draining:
                return

            # If handler drops out, sleep a retry
            await asyncio.sleep(1)

    async def _process_message(self, msg):
        """Process a single message with deferred acknowledgment"""
        # Store message for later acknowledgment
        msg_id = str(uuid.uuid4())
        self.pending_acks[msg_id] = msg
        
        try:
            id = msg.properties()["id"]
        except:
            id = None
            
        value = msg.value()
        delivery_success = False
        
        async with self.lock:
            # Deliver to specific subscribers
            if id in self.q:
                delivery_success = await self._deliver_to_queue(
                    self.q[id], value
                )
            
            # Deliver to all subscribers
            for q in self.full.values():
                if await self._deliver_to_queue(q, value):
                    delivery_success = True
        
        # Acknowledge only on successful delivery
        if delivery_success:
            self.consumer.acknowledge(msg)
            del self.pending_acks[msg_id]
        else:
            # Negative acknowledge for retry
            self.consumer.negative_acknowledge(msg)
            del self.pending_acks[msg_id]
                
    async def _deliver_to_queue(self, queue, value):
        """Deliver message to queue with backpressure handling"""
        try:
            if self.backpressure_strategy == "block":
                # Block until space available (no timeout)
                await queue.put(value)
                return True
                
            elif self.backpressure_strategy == "drop_oldest":
                # Drop oldest message if queue full
                if queue.full():
                    try:
                        queue.get_nowait()
                        if self.metrics:
                            self.metrics.dropped()
                    except asyncio.QueueEmpty:
                        pass
                await queue.put(value)
                return True
                
            elif self.backpressure_strategy == "drop_new":
                # Drop new message if queue full
                if queue.full():
                    if self.metrics:
                        self.metrics.dropped()
                    return False
                await queue.put(value)
                return True
                
        except Exception as e:
            logger.error(f"Failed to deliver message: {e}")
            return False

主要设计优势（与发布者模式匹配）： <<<<<<< HEAD 单一处理位置： 所有消息处理都在 run() 方法中进行。

单一处理位置： 所有消息处理都发生在 run() 方法中。

82edf2d (New md files from RunPod) 清晰的状态机： 三个明确的状态 - 运行中、正在排空、已停止。 排空期间暂停： 在排空现有队列时，停止从 Pulsar 接收新消息。 超时保护： 在排空过程中不会无限期挂起。 正确的清理： 在关闭时，会对任何未发送的消息进行否定确认。

B. 导出处理程序改进

文件： trustgraph-flow/trustgraph/gateway/dispatch/triples_export.py

class TriplesExport:
    async def destroy(self):
        """Enhanced destroy with graceful shutdown"""
        # Step 1: Signal stop to prevent new messages
        self.running.stop()
        
        # Step 2: Wait briefly for in-flight messages
        await asyncio.sleep(0.5)
        
        # Step 3: Unsubscribe and stop subscriber (triggers queue drain)
        if hasattr(self, 'subs'):
            await self.subs.unsubscribe_all(self.id)
            await self.subs.stop()
        
        # Step 4: Close websocket last
        if self.ws and not self.ws.closed:
            await self.ws.close()
            
    async def run(self):
        """Enhanced run with better error handling"""
        self.subs = Subscriber(
            client = self.pulsar_client, 
            topic = self.queue,
            consumer_name = self.consumer, 
            subscription = self.subscriber,
            schema = Triples,
            backpressure_strategy = "block"  # Configurable
        )
        
        await self.subs.start()
        
        self.id = str(uuid.uuid4())
        q = await self.subs.subscribe_all(self.id)
        
        consecutive_errors = 0
        max_consecutive_errors = 5
        
        while self.running.get():
            try:
                resp = await asyncio.wait_for(q.get(), timeout=0.5)
                await self.ws.send_json(serialize_triples(resp))
                consecutive_errors = 0  # Reset on success
                
            except asyncio.TimeoutError:
                continue
                
            except queue.Empty:
                continue
                
            except Exception as e:
                logger.error(f"Exception sending to websocket: {str(e)}")
                consecutive_errors += 1
                
                if consecutive_errors >= max_consecutive_errors:
                    logger.error("Too many consecutive errors, shutting down")
                    break
                    
                # Brief pause before retry
                await asyncio.sleep(0.1)
        
        # Graceful cleanup handled in destroy()

3. Socket 级别改进

文件: trustgraph-flow/trustgraph/gateway/endpoint/socket.py

class SocketEndpoint:
    async def listener(self, ws, dispatcher, running):
        """Enhanced listener with graceful shutdown"""
        async for msg in ws:
            if msg.type == WSMsgType.TEXT:
                await dispatcher.receive(msg)
                continue
            elif msg.type == WSMsgType.BINARY:
                await dispatcher.receive(msg)
                continue
            else:
                # Graceful shutdown on close
                logger.info("Websocket closing, initiating graceful shutdown")
                running.stop()
                
                # Allow time for dispatcher cleanup
                await asyncio.sleep(1.0)
                break
                
    async def handle(self, request):
        """Enhanced handler with better cleanup"""
        # ... existing setup code ...
        
        try:
            async with asyncio.TaskGroup() as tg:
                running = Running()
                
                dispatcher = await self.dispatcher(
                    ws, running, request.match_info
                )
                
                worker_task = tg.create_task(
                    self.worker(ws, dispatcher, running)
                )
                
                lsnr_task = tg.create_task(
                    self.listener(ws, dispatcher, running)
                )
                
        except ExceptionGroup as e:
            logger.error("Exception group occurred:", exc_info=True)
            
            # Attempt graceful dispatcher shutdown
            try:
                await asyncio.wait_for(
                    dispatcher.destroy(), 
                    timeout=5.0
                )
            except asyncio.TimeoutError:
                logger.warning("Dispatcher shutdown timed out")
            except Exception as de:
                logger.error(f"Error during dispatcher cleanup: {de}")
                
        except Exception as e:
            logger.error(f"Socket exception: {e}", exc_info=True)
            
        finally:
            # Ensure dispatcher cleanup
            if dispatcher and hasattr(dispatcher, 'destroy'):
                try:
                    await dispatcher.destroy()
                except:
                    pass
                    
            # Ensure websocket is closed
            if ws and not ws.closed:
                await ws.close()
                
        return ws

配置选项

添加配置支持，用于调整行为：

# config.py
class GracefulShutdownConfig:
    # Publisher settings
    PUBLISHER_DRAIN_TIMEOUT = 5.0  # Seconds to wait for queue drain
    PUBLISHER_FLUSH_TIMEOUT = 2.0  # Producer flush timeout
    
    # Subscriber settings  
    SUBSCRIBER_DRAIN_TIMEOUT = 5.0  # Seconds to wait for queue drain
    BACKPRESSURE_STRATEGY = "block"  # Options: "block", "drop_oldest", "drop_new"
    SUBSCRIBER_MAX_QUEUE_SIZE = 100  # Maximum queue size before backpressure
    
    # Socket settings
    SHUTDOWN_GRACE_PERIOD = 1.0  # Seconds to wait for graceful shutdown
    MAX_CONSECUTIVE_ERRORS = 5  # Maximum errors before forced shutdown
    
    # Monitoring
    LOG_QUEUE_STATS = True  # Log queue statistics on shutdown
    METRICS_ENABLED = True  # Enable metrics collection

测试策略

单元测试

async def test_publisher_queue_drain():
    """Verify Publisher drains queue on shutdown"""
    publisher = Publisher(...)
    
    # Fill queue with messages
    for i in range(10):
        await publisher.send(f"id-{i}", {"data": i})
    
    # Stop publisher
    await publisher.stop()
    
    # Verify all messages were sent
    assert publisher.q.empty()
    assert mock_producer.send.call_count == 10

async def test_subscriber_deferred_ack():
    """Verify Subscriber only acks on successful delivery"""
    subscriber = Subscriber(..., backpressure_strategy="drop_new")
    
    # Fill queue to capacity
    queue = await subscriber.subscribe("test")
    for i in range(100):
        await queue.put({"data": i})
    
    # Try to add message when full
    msg = create_mock_message()
    await subscriber._process_message(msg)
    
    # Verify negative acknowledgment
    assert msg.negative_acknowledge.called
    assert not msg.acknowledge.called

集成测试

async def test_import_graceful_shutdown():
    """Test import path handles shutdown gracefully"""
    # Setup
    import_handler = TriplesImport(...)
    await import_handler.start()
    
    # Send messages
    messages = []
    for i in range(100):
        msg = {"metadata": {...}, "triples": [...]}
        await import_handler.receive(msg)
        messages.append(msg)
    
    # Shutdown while messages in flight
    await import_handler.destroy()
    
    # Verify all messages reached Pulsar
    received = await pulsar_consumer.receive_all()
    assert len(received) == 100

async def test_export_no_message_loss():
    """Test export path doesn't lose acknowledged messages"""
    # Setup Pulsar with test messages
    for i in range(100):
        await pulsar_producer.send({"data": i})
    
    # Start export handler
    export_handler = TriplesExport(...)
    export_task = asyncio.create_task(export_handler.run())
    
    # Receive some messages
    received = []
    for _ in range(50):
        msg = await websocket.receive()
        received.append(msg)
    
    # Force shutdown
    await export_handler.destroy()
    
    # Continue receiving until websocket closes
    while not websocket.closed:
        try:
            msg = await websocket.receive()
            received.append(msg)
        except:
            break
    
    # Verify no acknowledged messages were lost
    assert len(received) >= 50

部署计划

<<<<<<< HEAD

第一阶段：关键修复（第一周）

修复订阅者确认时序问题（防止消息丢失） 添加发布者队列排空功能 部署到测试环境

第二阶段：平滑关闭（第二周）

=======

第一阶段：关键修复 (第一周)

修复订阅者确认时序问题 (防止消息丢失) 添加发布者队列排空功能 部署到测试环境

第二阶段：平滑关闭 (第二周)

82edf2d (New md files from RunPod) 实施关闭协调 添加反压策略 性能测试

<<<<<<< HEAD

第三阶段：监控与调优（第三周）

=======

第三阶段：监控与调优 (第三周)

82edf2d (New md files from RunPod) 添加队列深度的指标 添加消息丢失的告警 根据生产数据调整超时值

监控与告警

跟踪指标

publisher.queue.depth - 当前发布者队列大小 publisher.messages.dropped - 关闭期间丢失的消息数量 subscriber.messages.negatively_acknowledged - 失败的交付 websocket.graceful_shutdowns - 成功的平滑关闭 websocket.forced_shutdowns - 强制/超时关闭

告警

<<<<<<< HEAD 发布者队列深度超过 80% 的容量

发布者队列深度超过 80% 容量

82edf2d (New md files from RunPod) 关闭期间出现任何消息丢失 订阅者否定确认率 > 1% 关闭超时

向后兼容性

所有更改都保持向后兼容性： 在没有配置的情况下，默认行为保持不变 现有部署继续正常运行 如果新的功能不可用，则会进行优雅降级

安全注意事项

没有引入新的攻击向量 反压可防止内存耗尽攻击 可配置的限制可防止资源滥用

性能影响

正常运行期间的开销很小 <<<<<<< HEAD 关闭可能需要长达 5 秒（可配置） 内存使用量受队列大小限制 CPU 影响可以忽略不计（<1% 的增加）

关闭可能需要长达 5 秒钟 (可配置) 内存使用量受队列大小限制 CPU 影响可以忽略不计 (<1% 的增长)

82edf2d (New md files from RunPod)