Eventing on GCP

[Alberto Degli Esposti]

Hello,

I am currently using Knative on GKE and I am particularly interested in the eventing part. Since I am using GCP, I would prefer to use PubSub as my broker implementation. However, it seems that this is no longer possible as the https://github.com/google/knative-gcp project is no longer being maintained.  Maybe because from Google's standpoint, CloudRun serves as Knative serving managed version, with Eventarc functioning as its eventing counterpart. Unfortunately, there seems to be no method to attain similar flexibility at present. While I can use Eventarc to create triggers from events outside the cluster, it is not possible to do so from the inside. Instead of addressable sinks, I can publish events on PubSub topics from my services and create Eventarc destinations for those topics on my services in the cluster. However, I cannot create triggers based on the internal event type or other attributes. Additionally, I can only create a single subscription, over which I have no control. I can create one single topic having as destination an internal broker maybe in his default implementation, but it is just an half solution. It does not make too much sense to me. 

My question is, am I missing something on how eventarc can replace the previous support offered by Google on knative eventing or I have to definitely resign and abandon this path in favor of a different solution? As you may have guessed, I would like to avoid introducing Kafka into my architecture

Thank You

[Sebastien Goasguen]

Hi Alberto,

I cannot comment on eventarc but I believe that you are correct in that you won't be able to filter based on cloudevents metadata.

My shameless plug is that at triggermesh we have a GooglePubSub event source and a GooglePubSub event sink (aka target) that may help you do what you are after without going through eventarc. You would be able to use a knative broker or a triggermesh broker.

See: 

• https://docs.triggermesh.io/1.24/sources/googlecloudpubsub/
• https://docs.triggermesh.io/1.24/targets/googlecloudpubsub/

Hope that helps,

-Sebastien

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[Alberto Degli Esposti]

Hello Sebastien,

Thanks for your reply and your suggestion, I will consider triggermesh as an alternative to eventarc and if I understand correctly from the documentation I can provide the subscriptionId to the GoogleCloudPubSubSource CR. This would allow me to have multiple subscriptions for a single topic, where I can already create filters based on message attributes. This allows me to bypass the knative triggers but get the same result.

I hope I understood correctly why this would solve my problem by completely replacing the internal broker with pubsub

Thanks again

Alberto