Publishing & subscribing messages without CloudEvents

Learn when you might not use CloudEvents and how to disable them.

When adding Dapr to your application, some services may still need to communicate via pub/sub messages not encapsulated in CloudEvents, due to either compatibility reasons or some apps not using Dapr. These are referred to as “raw” pub/sub messages. Dapr enables apps to publish and subscribe to raw events not wrapped in a CloudEvent for compatibility.

Publishing raw messages

Dapr apps are able to publish raw events to pub/sub topics without CloudEvent encapsulation, for compatibility with non-Dapr apps.

Warning

Not using CloudEvents disables support for tracing, event deduplication per messageId, content-type metadata, and any other features built using the CloudEvent schema.

To disable CloudEvent wrapping, set the rawPayload metadata to true as part of the publishing request. This allows subscribers to receive these messages without having to parse the CloudEvent schema.

• curl
• Python SDK
• PHP SDK

curl -X "POST" http://localhost:3500/v1.0/publish/pubsub/TOPIC_A?metadata.rawPayload=true -H "Content-Type: application/json" -d '{"order-number": "345"}'

from dapr.clients import DaprClient
with DaprClient() as d:
    req_data = {
        'order-number': '345'
    }
    # Create a typed message with content type and body
    resp = d.publish_event(
        pubsub_name='pubsub',
        topic_name='TOPIC_A',
        data=json.dumps(req_data),
        publish_metadata={'rawPayload': 'true'}
    )
    # Print the request
    print(req_data, flush=True)

<?php
require_once __DIR__.'/vendor/autoload.php';
$app = \Dapr\App::create();
$app->run(function(\DI\FactoryInterface $factory) {
    $publisher = $factory->make(\Dapr\PubSub\Publish::class, ['pubsub' => 'pubsub']);
    $publisher->topic('TOPIC_A')->publish('data', ['rawPayload' => 'true']);
});

Subscribing to raw messages

Dapr apps are also able to subscribe to raw events coming from existing pub/sub topics that do not use CloudEvent encapsulation.

Programmatically subscribe to raw events

When subscribing programmatically, add the additional metadata entry for rawPayload so the Dapr sidecar automatically wraps the payloads into a CloudEvent that is compatible with current Dapr SDKs.

• Python
• PHP SDK

import flask
from flask import request, jsonify
from flask_cors import CORS
import json
import sys
app = flask.Flask(__name__)
CORS(app)
@app.route('/dapr/subscribe', methods=['GET'])
def subscribe():
    subscriptions = [{'pubsubname': 'pubsub',
                      'topic': 'deathStarStatus',
                      'route': 'dsstatus',
                      'metadata': {
                          'rawPayload': 'true',
                      } }]
    return jsonify(subscriptions)
@app.route('/dsstatus', methods=['POST'])
def ds_subscriber():
    print(request.json, flush=True)
    return json.dumps({'success':True}), 200, {'ContentType':'application/json'}
app.run()

<?php
require_once __DIR__.'/vendor/autoload.php';
$app = \Dapr\App::create(configure: fn(\DI\ContainerBuilder $builder) => $builder->addDefinitions(['dapr.subscriptions' => [
    new \Dapr\PubSub\Subscription(pubsubname: 'pubsub', topic: 'deathStarStatus', route: '/dsstatus', metadata: [ 'rawPayload' => 'true'] ),
]]));
$app->post('/dsstatus', function(
    #[\Dapr\Attributes\FromBody]
    \Dapr\PubSub\CloudEvent $cloudEvent,
    \Psr\Log\LoggerInterface $logger
    ) {
        $logger->alert('Received event: {event}', ['event' => $cloudEvent]);
        return ['status' => 'SUCCESS'];
    }
);
$app->start();

Declaratively subscribe to raw events

Similarly, you can subscribe to raw events declaratively by adding the rawPayload metadata entry to your subscription specification.

apiVersion: dapr.io/v1alpha1
kind: Subscription
metadata:
  name: myevent-subscription
spec:
  topic: deathStarStatus
  route: /dsstatus
  pubsubname: pubsub
  metadata:
    rawPayload: "true"
scopes:
- app1
- app2

Next steps

• Learn more about publishing and subscribing messages
• List of pub/sub components
• Read the API reference

Last modified June 20, 2022: Upmerge 1.7 into 1.8 [2022-06-20] (#2546) (e540cebb)