mirror of https://github.com/dapr/docs.git
141 lines
3.3 KiB
Markdown
141 lines
3.3 KiB
Markdown
---
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type: docs
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title: "Pub/sub API reference"
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linkTitle: "Pub/Sub API"
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description: "Detailed documentation on the pub/sub API"
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weight: 300
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---
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## Publish a message to a given topic
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This endpoint lets you publish data to multiple consumers who are listening on a `topic`.
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Dapr guarantees at least once semantics for this endpoint.
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### HTTP Request
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```
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POST http://localhost:<daprPort>/v1.0/publish/<pubsubname>/<topic>
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```
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### HTTP Response codes
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Code | Description
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---- | -----------
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204 | Message delivered
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403 | Message forbidden by access controls
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404 | No pubsub name or topic given
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500 | Delivery failed
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### URL Parameters
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Parameter | Description
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--------- | -----------
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daprPort | the Dapr port
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pubsubname | the name of pubsub component.
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topic | the name of the topic
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> Note, all URL parameters are case-sensitive.
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```shell
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curl -X POST http://localhost:3500/v1.0/publish/pubsubName/deathStarStatus \
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-H "Content-Type: application/json" \
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-d '{
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"status": "completed"
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}'
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```
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## Optional Application (User Code) Routes
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### Provide a route for Dapr to discover topic subscriptions
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Dapr will invoke the following endpoint on user code to discover topic subscriptions:
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#### HTTP Request
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```
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GET http://localhost:<appPort>/dapr/subscribe
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```
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#### URL Parameters
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Parameter | Description
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--------- | -----------
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appPort | the application port
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#### HTTP Response body
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A json encoded array of strings.
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Example:
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```json
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[
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{
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"pubsubname": "pubsub",
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"topic": "newOrder",
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"route": "/orders"
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}
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]
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```
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> Note, all subscription parameters are case-sensitive.
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### Provide route(s) for Dapr to deliver topic events
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In order to deliver topic events, a `POST` call will be made to user code with the route specified in the subscription response.
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The following example illustrates this point, considering a subscription for topic `newOrder` with route `orders` on port 3000: `POST http://localhost:3000/orders`
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#### HTTP Request
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```
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POST http://localhost:<appPort>/<path>
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```
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> Note, all URL parameters are case-sensitive.
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#### URL Parameters
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Parameter | Description
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--------- | -----------
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appPort | the application port
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path | route path from the subscription configuration
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#### Expected HTTP Response
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An HTTP 2xx response denotes successful processing of message.
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For richer response handling, a JSON encoded payload body with the processing status can be sent:
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```json
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{
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"status": "<status>"
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}
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```
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Status | Description
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--------- | -----------
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SUCCESS | message is processed successfully
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RETRY | message to be retried by Dapr
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DROP | warning is logged and message is dropped
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Others | error, message to be retried by Dapr
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Dapr assumes a JSON encoded payload response without `status` field or an empty payload responses with HTTP 2xx, as `SUCCESS`.
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The HTTP response might be different from HTTP 2xx, the following are Dapr's behavior in different HTTP statuses:
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HTTP Status | Description
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--------- | -----------
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2xx | message is processed as per status in payload (`SUCCESS` if empty; ignored if invalid payload).
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404 | error is logged and message is dropped
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other | warning is logged and message to be retried
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## Message envelope
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Dapr Pub/Sub adheres to version 1.0 of Cloud Events.
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## Related links
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* [How to publish to and consume topics]({{< ref howto-publish-subscribe.md >}})
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* [Sample for pub/sub](https://github.com/dapr/quickstarts/tree/master/pub-sub)
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