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

---
layout: default
title: "Especificação Técnica de Desligamento Gratuito de Importação/Exportação"
parent: "Portuguese (Beta)"
---

# Especificação Técnica de Desligamento Gratuito de Importação/Exportação

> **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.

## Declaração do Problema

Atualmente, o gateway TrustGraph experimenta perda de mensagens durante o fechamento do WebSocket tanto em operações de importação quanto de exportação. Isso ocorre devido a condições de corrida em que as mensagens em trânsito são descartadas antes de atingir seu destino (filas Pulsar para importações, clientes WebSocket para exportações).

### Problemas no Lado da Importação
1. O buffer da fila asyncio do publicador não é esvaziado durante o desligamento.
2. O WebSocket é fechado antes de garantir que as mensagens enfileiradas cheguem ao Pulsar.
3. Não há mecanismo de confirmação para a entrega bem-sucedida da mensagem.

### Problemas no Lado da Exportação
1. As mensagens são confirmadas no Pulsar antes da entrega bem-sucedida aos clientes.
2. Os tempos limite fixos causam a perda de mensagens quando as filas estão cheias.
3. Não há mecanismo de controle de fluxo para lidar com consumidores lentos.
4. Múltiplos pontos de buffer onde os dados podem ser perdidos.

## Visão Geral da Arquitetura

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

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

## Correções Propostas

### 1. Melhorias no Publicador (Lado da Importação)

#### A. Esvaziamento Gratuito da Fila

**Arquivo**: `trustgraph-base/trustgraph/base/publisher.py`

```python
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))
```

**Principais Vantagens do Design:**
<<<<<<< HEAD
**Local de Envio Único**: Todas as chamadas de `producer.send()` ocorrem em um único local dentro do método `run()`.
=======
**Local de Envio Único**: Todas as chamadas `producer.send()` ocorrem em um único local dentro do método `run()`.
>>>>>>> 82edf2d (New md files from RunPod)
**Máquina de Estados Clara**: Três estados claros - em execução, esvaziando, parado.
**Proteção por Timeout**: Não fica indefinidamente travado durante o esvaziamento.
**Melhor Observabilidade**: Registro claro do progresso do esvaziamento e das transições de estado.
**Rejeição de Mensagens Opcional**: Pode rejeitar novas mensagens durante a fase de desligamento.

#### B. Ordem de Desligamento Aprimorada

**Arquivo**: `trustgraph-flow/trustgraph/gateway/dispatch/triples_import.py`

```python
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. Melhorias para o Assinante (Lado de Exportação)

#### A. Padrão de Drenagem Integrado

**Arquivo**: `trustgraph-base/trustgraph/base/subscriber.py`

```python
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
```

<<<<<<< HEAD
**Principais Vantagens do Design (compatível com o padrão do Editor):**
**Local de Processamento Único**: Todo o processamento de mensagens ocorre no método `run()`
**Máquina de Estados Clara**: Três estados claros - em execução, esvaziando, parado
**Pausa Durante o Esvaziamento**: Interrompe a aceitação de novas mensagens do Pulsar enquanto esvazia as filas existentes
**Proteção por Timeout**: Não fica indefinidamente travado durante o esvaziamento
=======
**Principais Vantagens do Design (compatível com o padrão do Publicador):**
**Local de Processamento Único**: Todo o processamento de mensagens ocorre no método `run()`
**Máquina de Estados Clara**: Três estados claros - em execução, esvaziando, parado
**Pausa Durante o Esvaziamento**: Interrompe a aceitação de novas mensagens do Pulsar enquanto esvazia as filas existentes
**Proteção por Timeout**: Não fica indefinidamente bloqueado durante o esvaziamento
>>>>>>> 82edf2d (New md files from RunPod)
**Limpeza Adequada**: Reconhece negativamente quaisquer mensagens não entregues durante o desligamento

#### B. Melhorias no Manipulador de Exportação

**Arquivo**: `trustgraph-flow/trustgraph/gateway/dispatch/triples_export.py`

```python
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. Melhorias no Nível de Socket

**Arquivo**: `trustgraph-flow/trustgraph/gateway/endpoint/socket.py`

```python
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
```

## Opções de Configuração

Adicionar suporte para configuração para ajustar o comportamento:

```python
# 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
```

## Estratégia de Testes

### Testes Unitários

```python
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
```

### Testes de Integração

```python
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
```

## Plano de Implementação

### Fase 1: Correções Críticas (Semana 1)
Corrigir o tempo de reconhecimento do assinante (evitar perda de mensagens)
Adicionar esvaziamento da fila do publicador
Implantar no ambiente de teste

### Fase 2: Desligamento Gradual (Semana 2)
<<<<<<< HEAD
Implementar coordenação de desligamento
=======
Implementar a coordenação de desligamento
>>>>>>> 82edf2d (New md files from RunPod)
Adicionar estratégias de backpressure
Testes de desempenho

### Fase 3: Monitoramento e Ajuste (Semana 3)
Adicionar métricas para profundidade da fila
Adicionar alertas para perda de mensagens
Ajustar valores de timeout com base em dados de produção

## Monitoramento e Alertas

### Métricas a serem Monitoradas
`publisher.queue.depth` - Tamanho atual da fila do publicador
`publisher.messages.dropped` - Mensagens perdidas durante o desligamento
`subscriber.messages.negatively_acknowledged` - Entregas falhadas
`websocket.graceful_shutdowns` - Desligamentos graduais bem-sucedidos
`websocket.forced_shutdowns` - Desligamentos forçados/por timeout

### Alertas
Profundidade da fila do publicador > 80% da capacidade
Qualquer perda de mensagens durante o desligamento
Taxa de reconhecimento negativo do assinante > 1%
Timeout de desligamento excedido

## Compatibilidade com Versões Anteriores

Todas as alterações mantêm a compatibilidade com versões anteriores:
Comportamento padrão inalterado sem configuração
Implantações existentes continuam a funcionar
Degradação gradual se novos recursos não estiverem disponíveis

## Considerações de Segurança

Nenhum novo vetor de ataque introduzido
O backpressure impede ataques de esgotamento de memória
<<<<<<< HEAD
Limites configuráveis ​​evitam o abuso de recursos
=======
Limites configuráveis evitam o abuso de recursos
>>>>>>> 82edf2d (New md files from RunPod)

## Impacto no Desempenho

Sobrecarga mínima durante a operação normal
O desligamento pode levar até 5 segundos a mais (configurável)
O uso de memória é limitado pelos limites do tamanho da fila
O impacto na CPU é insignificante (<1% de aumento)