Basics

Separation of dependencies

Propan supports various message brokers using special classes:

RedisRabbitMQKafkaSQSNATS

from propan import RedisBroker

from propan import RabbitBroker

from propan import KafkaBroker

from propan import SQSBroker

from propan import NatsBroker

Be careful! Different brokers require different dependencies. If you have not installed these dependencies, the imported broker will have the None value.

To install Propan with the necessary dependencies for your broker, select one of the installation options:

RedisRabbitMQKafkaSQSNATS

pip install "propan[async-redis]"

pip install "propan[async-rabbit]"

pip install "propan[async-kafka]"

pip install "propan[async-sqs]"

pip install "propan[async-nats]"

Broker Initialization

Data for connecting Propan Broker to your message broker can be transmitted in 2 ways:

RedisRabbitMQKafkaSQSNATS

1. In the broker constructor

   from propan import RedisBroker
   broker = RedisBroker("redis://localhost:6379/")
   

2. In the connect method

   from propan import RedisBroker
   broker = RedisBroker()
   ...
   await broker.connect("redis://localhost:6379/")
   

1. In the broker constructor

   from propan import RabbitBroker
   broker = RabbitBroker("amqp://guest:guest@localhost:5672/")
   

2. In the connect method

   from propan import RabbitBroker
   broker = RabbitBroker()
   ...
   await broker.connect("amqp://guest:guest@localhost:5672/")
   

1. In the broker constructor

   from propan import KafkaBroker
   broker = KafkaBroker("localhost:9092")
   

2. In the connect method

   from propan import KafkaBroker
   broker = KafkaBroker()
   ...
   await broker.connect("localhost:9092")
   

1. In the broker constructor

   from propan import SQSBroker
   broker = SQSBroker("http://localhost:9324")
   

2. In the connect method

   from propan import SQSBroker
   broker = SQSBroker()
   ...
   await broker.connect("http://localhost:9324")
   

1. In the broker constructor

   from propan import NatsBroker
   broker = NatsBroker("nats://localhost:4222")
   

2. In the connect method

   from propan import NatsBroker
   broker = NatsBroker()
   ...
   await broker.connect("nats://localhost:4222")
   

In the simplest case, initializing through the constructor is enough for most use cases.

However, if you need more granularity in a complex scenario, for example, when configuring a project via environment variables, you may need the second option. The full example is described here.

Note

The parameters passed to connect override the parameters passed to the constructor. Be careful with this.

In addition, calling connect again will have no effect. Therefore, you do not have to worry that broker.start() call (used inside PropanApp to run the broker) will cause any errors.