Publish/Subscribe Operations | Fern Documentation

Operations in AsyncAPI are defined underneath the operations key, with channels defined under the channels key. Below is an example of defining publish and subscribe operations:

asyncapi.yml

1 channels:
2   user/notifications:
3     address: user/notifications
4     messages:
5       UserNotification:
6         $ref: '#/components/messages/UserNotification'
7 
8 operations:
9   onUserNotification:
10     action: receive
11     channel:
12       $ref: '#/channels/user~1notifications'
13     summary: Receive user notifications
14     description: Subscribe to user notification events
15   sendUserNotification:
16     action: send
17     channel:
18       $ref: '#/channels/user~1notifications'
19     summary: Send user notification
20     description: Publish a user notification event

Message examples

You can provide examples of messages by using the examples key in your message definitions:

asyncapi.yml

1 components:
2   messages:
3     UserNotification:
4       name: UserNotification
5       title: User Notification
6       summary: Notification sent to a user
7       contentType: application/json
8       payload:
9         $ref: '#/components/schemas/Notification'
10       examples:
11         - name: EmailNotification
12           summary: Example email notification
13           payload:
14             userId: "123e4567-e89b-12d3-a456-426614174000"
15             type: "email"
16             message: "Welcome to our service!"
17             priority: "medium"

Publish operations

Publish operations represent messages that your service sends to a channel:

asyncapi.yml

1 operations:
2   publishOrderStatus:
3     action: send
4     channel:
5       $ref: '#/channels/order~1status'
6     summary: Publish order status update
7     description: Send order status updates to subscribers
8     message:
9       $ref: '#/components/messages/OrderStatus'

Subscribe operations represent messages that your service receives from a channel:

asyncapi.yml

1 operations:
2   subscribeToUserSignups:
3     action: receive
4     channel:
5       $ref: '#/channels/user~1signup'
6     summary: Subscribe to user signups
7     description: Receive notifications when users sign up
8     message:
9       $ref: '#/components/messages/UserSignup'

Bi-directional communication

You can define both publish and subscribe operations for the same channel to enable bi-directional communication:

asyncapi.yml

1 operations:
2   sendChatMessage:
3     action: send
4     channel:
5       $ref: '#/channels/chat~1room'
6     summary: Send chat message
7     description: Send a message to a chat room
8   receiveChatMessage:
9     action: receive
10     channel:
11       $ref: '#/channels/chat~1room'
12     summary: Receive chat message
13     description: Receive messages from a chat room