Add the RabbitMQ consumer

.env.docker

@@ -1,2 +1,3 @@
 REDIS_URL=redis://redis:6379/0
-DATABASE_URL=psql://postgres:postgres@db:5432/postgres
+DATABASE_URL=postgresql+asyncpg://postgres:postgres@db:5432/postgres
+RABBITMQ_AMPQ_URL=amqp://guest:guest@rabbitmq:5672/

.env.sample

@@ -1,2 +1,3 @@
 REDIS_URL=redis://redis:6379/0
-DATABASE_URL=postgresql+asyncpg://postgres:postgres@db:5432/postgres
+DATABASE_URL=postgresql+asyncpg://postgres:postgres@db:5432/postgres
+RABBITMQ_AMPQ_URL=amqp://guest:guest@rabbitmq:5672/

.env.test

@@ -2,3 +2,4 @@ TEST=True
 REDIS_URL=redis://localhost:6379/0
 DATABASE_URL=postgresql+asyncpg://postgres:postgres@localhost:5432/postgres
 DATABASE_POOL_CLASS=NullPool
+RABBITMQ_AMQP_URL=amqp://guest:guest@localhost:5672/

.github/workflows/ci.yml

@@ -53,6 +53,15 @@ jobs:
           --health-retries 5
         ports:
           - 5432:5432
+      rabbitmq:
+        image: rabbitmq:alpine
+        ports:
+          - 5672:5672
+        options: >-
+          --health-cmd "rabbitmqctl await_startup"
+          --health-interval 10s
+          --health-timeout 5s
+          --health-retries 5
     steps:
     - uses: actions/checkout@v4
     - name: Set up Python ${{ matrix.python-version }}

app/config.py

@@ -14,11 +14,14 @@ class Settings(BaseSettings):
         extra="allow",
         case_sensitive=True,
     )
+    TEST: bool = False
     REDIS_URL: str = "redis://"
     DATABASE_URL: str = "psql://postgres:"
     DATABASE_POOL_CLASS: str = "AsyncAdaptedQueuePool"
     DATABASE_POOL_SIZE: int = 10
-    TEST: bool = False
+    RABBITMQ_AMPQ_URL: str = "amqp://guest:guest@"
+    RABBITMQ_AMQP_EXCHANGE: str = "safe-transaction-service-events"
+    RABBITMQ_DECODER_EVENTS_QUEUE_NAME: str = "safe-decoder-service"
 
 
 settings = Settings()

app/datasources/queue/queue_provider.py

@@ -0,0 +1,136 @@
+from asyncio import AbstractEventLoop
+from typing import Any, Callable
+
+import aio_pika
+from aio_pika.abc import (
+    AbstractExchange,
+    AbstractIncomingMessage,
+    AbstractQueue,
+    AbstractRobustConnection,
+    ConsumerTag,
+    ExchangeType,
+)
+
+from app.config import settings
+
+
+class QueueProviderException(Exception):
+    """
+    Generic exception for QueueProvider errors.
+    """
+
+    pass
+
+
+class QueueProviderUnableToConnectException(QueueProviderException):
+    """
+    Raised when a connection to RabbitMQ cannot be established.
+    """
+
+    pass
+
+
+class QueueProviderNotConnectedException(QueueProviderException):
+    """
+    Raised when no connection is established.
+    """
+
+    pass
+
+
+class QueueProvider:
+
+    _connection: AbstractRobustConnection | None
+    _exchange: AbstractExchange | None
+    _events_queue: AbstractQueue | None
+
+    def __init__(self) -> None:
+        """
+        Initializes the QueueProvider instance with default values.
+        """
+        self._connection = None
+        self._exchange = None
+        self._events_queue = None
+
+    async def _connect(self, loop: AbstractEventLoop) -> None:
+        """
+        Establishes a connection to RabbitMQ and sets up the exchange and queue.
+
+        :param loop: The asyncio event loop used for the connection.
+        :return:
+        """
+        try:
+            self._connection = await aio_pika.connect_robust(
+                url=settings.RABBITMQ_AMPQ_URL, loop=loop
+            )
+        except aio_pika.exceptions.AMQPConnectionError as e:
+            raise QueueProviderUnableToConnectException(e)
+
+        channel = await self._connection.channel()
+        self._exchange = await channel.declare_exchange(
+            settings.RABBITMQ_AMQP_EXCHANGE, ExchangeType.FANOUT
+        )
+        self._events_queue = await channel.declare_queue(
+            settings.RABBITMQ_DECODER_EVENTS_QUEUE_NAME, durable=True
+        )
+        if self._events_queue:
+            await self._events_queue.bind(self._exchange)
+
+    async def connect(self, loop: AbstractEventLoop) -> None:
+        """
+        Ensures that the RabbitMQ connection is established.
+
+        :param loop: The asyncio event loop used to establish the connection.
+        :return:
+        """
+        if not self._connection:
+            await self._connect(loop)
+
+    def is_connected(self) -> bool:
+        """
+        Verifies if the connection to RabbitMQ is established.
+
+        :return: True` if the connection is established, `False` otherwise.
+        """
+        return self._connection is not None
+
+    async def disconnect(self) -> None:
+        """
+        Safely closes the RabbitMQ connection and cleans up resources.
+
+        :return:
+        """
+        if self._connection:
+            if self._events_queue and self._exchange:
+                await self._events_queue.unbind(exchange=self._exchange)
+                await self._events_queue.delete(if_unused=False, if_empty=False)
+            await self._connection.close()
+            self._exchange = None
+            self._connection = None
+            self._events_queue = None
+
+    async def consume(self, callback: Callable[[str], Any]) -> ConsumerTag:
+        """
+        Starts consuming messages from the declared queue.
+
+        - Each message is processed using the provided callback function.
+
+        :param callback: A function to process incoming messages.
+        :return: A tag identifying the active consumer.
+        :raises QueueProviderNotConnectedException: if no connection or queue is initialized.
+        """
+        if not self._connection or not self._events_queue:
+            raise QueueProviderNotConnectedException()
+
+        async def wrapped_callback(message: AbstractIncomingMessage) -> None:
+            """
+            Wrapper for processing the message and handling ACKs.
+
+            :param message: The incoming RabbitMQ message.
+            """
+            await message.ack()
+            body = message.body
+            if body:
+                callback(body.decode("utf-8"))
+
+        return await self._events_queue.consume(wrapped_callback)

app/main.py

@@ -1,14 +1,51 @@
+import asyncio
+import logging
+from contextlib import asynccontextmanager
+
 from fastapi import APIRouter, FastAPI
 
 from . import VERSION
+from .datasources.queue.queue_provider import (
+    QueueProvider,
+    QueueProviderUnableToConnectException,
+)
 from .routers import about, contracts, default
+from .services.events import EventsService
+
+
+@asynccontextmanager
+async def lifespan(app: FastAPI):
+    """
+    Define the lifespan of the application:
+    - Connects to the QueueProvider at startup.
+    - Disconnects from the QueueProvider at shutdown.
+    """
+    queue_provider = QueueProvider()
+    consume_task = None
+    try:
+        loop = asyncio.get_running_loop()
+        try:
+            await queue_provider.connect(loop)
+        except QueueProviderUnableToConnectException as e:
+            logging.error(f"Unable to connect to Queue Provider: {e}")
+        if queue_provider.is_connected():
+            consume_task = asyncio.create_task(
+                queue_provider.consume(EventsService.process_event)
+            )
+        yield
+    finally:
+        if consume_task:
+            consume_task.cancel()
+        await queue_provider.disconnect()
+
 
 app = FastAPI(
     title="Safe Decoder Service",
     description="Safe Core{API} decoder service",
     version=VERSION,
     docs_url=None,
     redoc_url=None,
+    lifespan=lifespan,
 )
 
 # Router configuration

app/services/events.py

@@ -0,0 +1,38 @@
+import json
+import logging
+from typing import Dict
+
+
+class EventsService:
+
+    @classmethod
+    def process_event(cls, message: str) -> None:
+        """
+        Processes the incoming event message.
+
+        :param message: The incoming message to process, expected to be a JSON string.
+        """
+        try:
+            tx_service_event = json.loads(message)
+
+            if cls.is_event_valid(tx_service_event):
+                # TODO: process event!
+                pass
+            else:
+                logging.error(
+                    f"Unsupported message. A valid message should have at least 'chainId' and 'type': {message}"
+                )
+        except json.JSONDecodeError:
+            logging.error(f"Unsupported message. Cannot parse as JSON: {message}")
+
+    @staticmethod
+    def is_event_valid(tx_service_event: Dict) -> bool:
+        """
+        Validates if the event has the required fields 'chainId' and 'type' as strings.
+
+        :param tx_service_event: The event object to validate.
+        :return: True if the event is valid (both 'chainId' and 'type' are strings), False otherwise.
+        """
+        return isinstance(tx_service_event.get("chainId"), str) and isinstance(
+            tx_service_event.get("type"), str
+        )

app/tests/datasources/queue/test_queue_provider.py

@@ -0,0 +1,59 @@
+import asyncio
+import unittest
+from unittest.mock import patch
+
+import aio_pika
+from aio_pika.abc import AbstractRobustConnection
+
+from app.config import settings
+from app.datasources.queue.queue_provider import (
+    QueueProvider,
+    QueueProviderUnableToConnectException,
+)
+
+
+class TestQueueProviderIntegration(unittest.IsolatedAsyncioTestCase):
+    async def asyncSetUp(self):
+        self.provider = QueueProvider()
+        self.loop = asyncio.get_event_loop()
+
+    async def test_connect_success(self):
+        self.assertFalse(self.provider.is_connected())
+        await self.provider.connect(self.loop)
+        self.assertTrue(self.provider.is_connected())
+        await self.provider.disconnect()
+        self.assertFalse(self.provider.is_connected())
+
+    async def test_connect_failure(self):
+        provider = QueueProvider()
+
+        with patch("app.config.settings.RABBITMQ_AMPQ_URL", "amqp://invalid-url"):
+            with self.assertRaises(QueueProviderUnableToConnectException):
+                await provider.connect(self.loop)
+
+    async def test_consume(self):
+        await self.provider.connect(self.loop)
+        assert isinstance(self.provider._connection, AbstractRobustConnection)
+        message = "Test message"
+        channel = await self.provider._connection.channel()
+        exchange = await channel.declare_exchange(
+            settings.RABBITMQ_AMQP_EXCHANGE, aio_pika.ExchangeType.FANOUT
+        )
+
+        await exchange.publish(
+            aio_pika.Message(body=message.encode("utf-8")),
+            routing_key="",
+        )
+
+        received_messages = []
+
+        def callback(message: str):
+            received_messages.append(message)
+
+        await self.provider.consume(callback)
+
+        # Wait to make sure the message is consumed.
+        await asyncio.sleep(1)
+
+        self.assertIn(message, received_messages)
+        await self.provider.disconnect()

app/tests/services/test_events.py

@@ -0,0 +1,50 @@
+import unittest
+from unittest.mock import patch
+
+from app.services.events import EventsService
+
+
+class TestEventsService(unittest.TestCase):
+
+    def test_is_event_valid(self):
+        valid_event = {"chainId": "123", "type": "transaction"}
+        self.assertTrue(EventsService.is_event_valid(valid_event))
+
+    def test_is_event_invalid(self):
+        invalid_event_missing_chain_id = {"type": "transaction"}
+        self.assertFalse(EventsService.is_event_valid(invalid_event_missing_chain_id))
+
+        invalid_event_missing_type = {"chainId": "123"}
+        self.assertFalse(EventsService.is_event_valid(invalid_event_missing_type))
+
+        invalid_event_invalid_chain_id = {"chainId": 123, "type": "transaction"}
+        self.assertFalse(EventsService.is_event_valid(invalid_event_invalid_chain_id))
+
+        invalid_event_invalid_type = {"chainId": "123", "type": 123}
+        self.assertFalse(EventsService.is_event_valid(invalid_event_invalid_type))
+
+    @patch("logging.error")
+    def test_process_event_valid_message(self, mock_log):
+        valid_message = '{"chainId": "123", "type": "transaction"}'
+
+        EventsService.process_event(valid_message)
+
+        mock_log.assert_not_called()
+
+    @patch("logging.error")
+    def test_process_event_invalid_json(self, mock_log):
+        invalid_message = '{"chainId": "123", "type": "transaction"'
+
+        EventsService.process_event(invalid_message)
+
+        mock_log.assert_called_with(
+            'Unsupported message. Cannot parse as JSON: {"chainId": "123", "type": "transaction"'
+        )
+
+        invalid_message_invalid_type = '{"chainId": "123", "type": 123}'
+
+        EventsService.process_event(invalid_message_invalid_type)
+
+        mock_log.assert_called_with(
+            'Unsupported message. A valid message should have at least \'chainId\' and \'type\': {"chainId": "123", "type": 123}'
+        )