When publishing a message allow setting Cloudevent attributes / Pub-Sub routing

Proposal

Hi,

As we have the Pub/Sub routing feature, it’ll be very useful to be able to set specific Cloudevent attributes when publishing the message.

At this point, the Publish implementation accepts only the message data, and there seems to be no other way to override the event.type or another attribute, other than making a direct HTTP request to the sidecar with the application/cloudevents+json raw data.

Another useful feature would be to specify tracing headers for scenarios like the outbox pattern where a separate process publishes the messages, in order to preserve correct tracing

[mcrio]

Hi @ChristianWeyer

Something along these lines:

// Dapr Json conventions
JsonSerializerOptions jsonOptions = new ();
jsonOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
jsonOptions.DictionaryKeyPolicy = JsonNamingPolicy.CamelCase;
jsonOptions.PropertyNameCaseInsensitive = true;

// `message` must be marked as object otherwise the serializer will serialize just the interface members
var cloudEvent = new { Type = routingKey, Data = (object)message };
string jsonCloudEvent = JsonSerializer.Serialize<object>(cloudEvent, jsonOptions);

var requestContent = new StringContent(
    jsonCloudEvent,
    Encoding.UTF8,
    "application/cloudevents+json"
);

var request = new HttpRequestMessage
{
    RequestUri = new Uri(
        $"/v1.0/publish/{pubSubName}/{topicName}",
        UriKind.Relative
    ),
    Method = HttpMethod.Post,
    Content = requestContent,
};
if (!string.IsNullOrWhiteSpace(traceIdentifier))
{
    request.Headers.Add("traceparent", traceIdentifier);
}

HttpResponseMessage response = await _httpClient.SendAsync(request).ConfigureAwait(false);

[mcrio]

Hi @ChristianWeyer I haven’t had yet the chance to try it out.