[SOLVED] GCP Log Router Sink Not Routing Logs to Topic?

GCP Log Router Sink Not Routing Logs to Topic?

Context: I am trying to store GCP Audit logs in a Pub/Sub topic via a Log Sink so I can pull those messages in a subscription (and have a 3rd party subscribe to that subscription).

Attempted solution :
Log Sink with inclusion filter of: logName:"cloudaudit.googleapis.com" to route logs to -> Pub/Sub Topic to store those messages -> Subscription (Pull Based) to view those messages.

Problem: Logs from the sink do not seem to be ending up in the topic. When I try to view the messages in the topic (by clicking pull in the GCP GUI), I get back no messages, even though I know for sure that audit logs exist (I ran a query against the inclusion filter above) and continue to be generated pretty frequently.

Question: Why aren't the logs being routed to the topic OR why isn't the topic showing the logs when I pull from the topic?

Solution

It's a permission issue. When you create a sink, this sink as an identity, you can get it like that

gcloud logging sinks describe \
 --format='value(writerIdentity)' <SINK_NAME>

Then, grant this identity the permission to publish to pubsub, for example

gcloud pubsub topics add-iam-policy-binding <TOPIC_ID> \
  --member=<WRITER_IDENTITY> --role=roles/pubsub.publisher

EDIT 1

Though the console

Go to the log router section, click on the 3 dot at the end of the line and view sink detail
From there a new windows display the writer identity, copy it
Eventually, go to PubSub topic, select the checkbox in front of your topic. Go to the right hand side panel, on permission, click on add member. here add your writer identity and select the corresponding role