Crate knien

Knien

Typed RabbitMQ interfacing for async Rust.

This crate defines several types of channels for interfacing with RabbitMQ in various ways:

• DirectChannel: a channel for publishing messages on direct queues.
• TopicChannel: a channel for publishing messages on topic exchanges
• RpcChannel: a channel for publishing messages on direct queues, allowing for receiving replies. It also supports publishing an initial message on a direct queue, and setting up a back-and-forth communincation channel.

RpcChannels currently require the tokio runtime to spawn tasks that receive messages and is therefore behind the rpc feature flag.

Each channel exposes methods to instantiate Publishers and Consumers, each of which are generic over the bus they publish on or consume from. These buses define what types of payload they send, so Publishers and Consumers can take care of serializing and deserializing the payloads and make sure the payloads they publish and yield are of the correct types.

There are several kinds of typed buses, each tied to one of the Channels:

• DirectBus: a bus that defines a PublishPayload type, a formatter for direct queue names, and the type of argument to that formatter. DirectBuses are used to simply publish messages on a direct queue without expecting any response. DirectBuses are tied to the DirectChannel.
• TopicBus: a bus that defines a PublishPayload type, a topic, and an Exchange. TopicBuses are used to publish and consume messages from a topic exchange. TopicBuses are tied to the TopicChannel.
• RpcBus: act like a DirectBus, but further defines a ReplyPayload type and allows for awaiting replies on sent messages. RpcBuses are tied to the RpcChannel
• RpcCommBus: a bus that defines InitialPayload, BackPayload and ForthPayload, and support flows where a single initial message is sent, after which back-and-forth a communication over which multiple messages can be sent is setup. RpcCommBuses are tied to the RpcChannel

Macros

direct_bus

Declare a new DirectBus.

rpc_bus

Declare a new RpcBus.

rpc_comm_bus

Declare a new RpcCommBus.

topic_bus

Declare a new TopicBus.

topic_exchange

Declare a new TopicExchange, specifying its type identifier and name.

Structs

BackReply

A reply on an RpcCommBus.

Connection

A connection to the RabbitMQ broker

Consumer

A consumer associated with a Channel and a Bus. Consumers implement futures::Stream, yielding Deliverys that are associated with the Bus.

ConsumerRoutingKey

A Routing key that can be used to consume messages from a TopicBus. ConsumerRoutingKeys cannot contain # and must be at least as concrete as TopicBus::TOPIC_PATTERN.

Delivery

A message that contains a payload associated with a bus

DirectChannel

A channel for publishing messages on direct queues.

ForthReply

A reply on an RpcCommBus.

Publisher

A publisher associated with a Channel and a Bus. Publishers allow for publishing messages with payloads of the Bus::PublishPayload type. Publishers take care of serializing the payloads before publishing.

PublisherRoutingKey

A Routing key that can be used to publish messages on a TopicBus. Can only represent concrete routing keys, i.e. routing keys cannot contain wildcards.

Reply

A reply to a Delivery that was sent onto a RpcBus

RpcChannel

A channel for publishing messages on direct queues, allowing for receiving replies using RpcBus. It also supports publishing an initial message on a direct queue, and setting up a back-and-forth communincation channel using RpcCommBus.

TopicChannel

A Topic Channel associated with a TopicExchange.

Enums

Error

This type represents anything that can go wrong when interacting with knien.

ReplyError

Error replying to a message. These errors should not occur if only knien-based application interact with the RabbitMQ broker

RoutingKeyError

Error indicating what went wrong in setting up a ConsumerRoutingKey or a PublisherRoutingKey

Traits

Bus

A Bus. Base trait for several other buses. This trait is best implemented by using one of the *_bus! macros this crate provices. If you are going to implement this trait manually, make sure you associate the correct Channel type to Bus::Chan:

Channel

A RrabbitMQ channel

DirectBus

A bus that allows publishing on a direct queue.

RpcBus

A bus that allows publishing messages on a direct queue, as well as replying to them.

RpcCommBus

An RPC-based communication bus that defines an InitialPayload, a BackPayload and ForthPayload, and supports flows where a single initial message is sent, after which back-and-forth a communication over which multiple messages can be sent is setup.

TopicBus

A bus that is associated with a TopicExchange, and defines a pattern of topics onto which messages can be publised and consumed

TopicExchange

A Topic Exchange

Type Aliases

Result

Alias for a Result with the error type Error.