Introduction
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AMQP 0-9-1 Overview
- The AMQP Protocol
- Connections & Channels
- Queues
- Messages
- Bindings
- Exchanges
- Vhost
- Publishers and Consumers
More Exchange Types
More Consumer Features
Queue Deep-dive
Other Features
Reliable Message Delivery
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Management HTTP API
Tutorials
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LavinMQ CLI
Delayed Message Exchange
There is no need to deliver every message at once. Some scenarios may require an order to process after a specific amount of time, or the system may need a chance to complete a setup process.
LavinMQ delayed exchange accomplishes this without needing extra code by delivering the messages after a predetermined amount of time.
What is a Delayed Message Exchange?
LavinMQ delayed exchange creates a waiting period between the time a message reaches an exchange and its delivery to a queue. You can specify an offset in milliseconds every time you publish a message.
When to use the Delayed Message Exchange?
Instantaneous delivery is not always the best option when processing messages. Delayed Message Exchange simplifies cases where there is a hard waiting period, a setup process, or you are trying to ensure that customers read your text messages.
Delayed Message Exchange
There are many use cases where a message delay is necessary. LavinMQ allows you to hold onto messages for a finite amount of time before delivery through the delayed message exchange.
LavinMQ delayed exchange creates a waiting period between the time a message reaches an exchange and its delivery to a queue. It lets you mimic standard exchange types. Messages are routed based on a designated type after the specified waiting period. Create direct, fanout, or even a custom exchange and complex topologies without the need for multiple extra layers.
No information is lost, as acknowledgment and other features trigger on arrival in the destination queue.
Creating a Delayed Message Exchange
Declare the exchange using a special x-delay-type parameter and the x-delayed-message type:
channel.exchange_declare(exchange='test-exchange',
exchange_type='x-delayed-message',
arguments={"x-delayed-type": "fanout"})The example exchange uses the fanout strategy. Messages reach each attached destination.
Add a delay to each message using the x-delay:
channel.basic_publish(exchange='test-exchange',
routing_key='test_route',
properties=pika.BasicProperties(
headers={'x-delay': 2500}
),
body='Hello World!')The target queue attached to the delayed_route receives the message after 2500 milliseconds. Set the header for whichever delay is needed.
Checking if a message was delayed
It is possible to ensure that messages process after a given delay. The exchange negates and returns the value passed in x-delay.
The value of x-delay becomes -4000 if you tell the delayed exchange to wait for 4000 milliseconds. The header never drops.
Ready to take the next steps? Here are some things you should keep in mind:
Managed LavinMQ instance on CloudAMQP
LavinMQ has been built with performance and ease of use in mind - we've benchmarked a throughput of about 1,000,000 messages/sec. You can try LavinMQ without any installation hassle by creating a free instance on CloudAMQP. Signing up is a breeze.
Help and feedback
We welcome your feedback and are eager to address any questions you may have about this piece or using LavinMQ. Join our Slack channel to connect with us directly. You can also find LavinMQ on GitHub.