docs/reference/api/pubsub.md

Pub Sub

Publish a message to a given topic

This endpoint lets you publish a payload to multiple consumers who are listening on a topic. Dapr guarantees at least once semantics for this endpoint.

HTTP Request

POST http://localhost:<daprPort>/v1.0/publish/<topic>

HTTP Response codes

Code	Description
200	Message delivered
500	Delivery failed

URL Parameters

Parameter	Description
daprPort	the Dapr port
topic	the name of the topic

curl -X POST http://localhost:3500/v1.0/publish/deathStarStatus \
  -H "Content-Type: application/json" \
 -d '{
       "status": "completed"
     }'

Handling topic subscriptions

In order to receive topic subscriptions, Dapr will invoke the following endpoint on user code:

HTTP Request

GET http://localhost:<appPort>/dapr/subscribe

URL Parameters

Parameter	Description
appPort	the application port

HTTP Response body

A json encoded array of strings.

Example:

"["TopicA","TopicB"]"

Delivering events to subscribers

In order to deliver events to a subscribed application, a POST call should be made to user code with the name of the topic as the URL path.

The following example illustrates this point, considering a subscription for topic TopicA:

HTTP Request

POST http://localhost:<appPort>/TopicA

URL Parameters

Parameter	Description
appPort	the application port

HTTP Response body

A JSON encoded payload.

Message Envelope

Dapr Pub/Sub adheres to version 0.3 of Cloud Events.