Exclude all attributes starting with "goog_" from outbound Pub/Sub headers

[elefeint]

Report came from Gitter -- in a Spring Cloud Stream application, HeaderMapper fields are not customizable in the adapters. In a Processor SCS application, if the Pub/Sub message received from one subscription is passed as-is to a topic, the message will be rejected with:

com.google.api.gax.rpc.InvalidArgumentException: io.grpc.StatusRuntimeException: INVALID_ARGUMENT: The request contains an attribute key that is not valid (key=googclient_deliveryattempt). Attribute keys must be non-empty and must not begin with 'goog' (case-insensitive).

To prevent this issue, PubSubHeaderMapper.outboundHeaderPatterns needs to include "!goog_* by default.

[ddixit14]

Sounds like something I can take up next? @elefeint

[elefeint]

Yes, that's a good idea. First, reproduce the issue by creating a sample application that has a Spring Cloud Stream processor -- our current sample only has a source and a sink.

[elefeint]

@ddixit14 Hints on reproducing using spring-cloud-gcp-pubsub-stream-functional-sample:

• googclient_deliveryattempt only exists when the subscription has DLQ enabled. Can't reproduce otherwise.
• In Spring Cloud Stream, to turn something from a Sink to a Processor, the functional bean needs to switch from being a Consumer (one input, no outputs) to being a Function (one input, one output).
• Once you have a processor/function, tie the outgoing stream to a physical Pub/Sub topic with this property: spring.cloud.stream.bindings.logUserMessage-out-0.destination=my-topic2

Bonus question to think about: do we want to strip incoming goog* headers, outgoing ones, or both?

[ddixit14]

Done hence closing the issue.