A queue allows processing of a message by a single consumer. In contrast to queues, topics and subscriptions provide a one-to-many form of communication in a publish and subscribe pattern. It’s useful for scaling to large numbers of recipients. Each published message is made available to each subscription registered with the topic. Publisher sends a message to a topic and one or more subscribers receive a copy of the message.
The subscriptions can use additional filters to restrict the messages that they want to receive. Publishers send messages to a topic in the same way that they send messages to a queue. But, consumers don’t receive messages directly from the topic. Instead, consumers receive messages from subscriptions of the topic. A topic subscription resembles a virtual queue that receives copies of the messages that are sent to the topic. Consumers receive messages from a subscription identically to the way they receive messages from a queue.
The message-sending functionality of a queue maps directly to a topic and its message-receiving functionality maps to a subscription. Among other things, this feature means that subscriptions support the same patterns described earlier in this section regarding queues: competing consumer, temporal decoupling, load leveling, and load balancing.
What is a topic in Azure?
A topic subscription resembles a virtual queue that receives copies of the messages that are sent to the topic. Consumers receive messages from a subscription identically to the way they receive messages from a queue.
What are topics and queues in Azure?
Queues and Topics are similar when a sender sends messages, but messages are processed differently by a receiver. A queue can have only one consumer, whereas a topic can have multiple subscribers.
Create a topic using the Azure portal
- On the Service Bus Namespace page, select Topics on the left menu.
- Select + Topic on the toolbar.
- Enter a name for the topic. Leave the other options with their default values.
- Select Create.
What is the difference between topic and subscription?
Topic. A named resource to which messages are sent by publishers. Subscription. A named resource representing the stream of messages from a single, specific topic, to be delivered to the subscribing application.
