Broker

Startup

Component opens connections to broker's gRPC server using root CA to verify certificate.
Component calls subscribe service (2-way streaming) and sends a registration event, which contains component name, commit, id, routes, and K8s SAT.
Broker authorizes by verifying SAT with K8s API and ensures claims match attributes provided by component.
The broker starts a subscription for the component that is used to pass events.
Broker puts component's registration into NATS k/v store using the component name + commit as key (not id).
Broker creates NATS consumer which listens for new messages on the component group's subject (evt.js.{compName}.{compCommit}).

Currently only HTTP server receives genesis events.
HTTP request comes in to http server and is converted to event.
If request contains deployment and environment headers/query params they are set on the event.
The default TTL, which can be set as a flag on broker, is set on event.
http server records request event id in map.
sends event to broker for routing
http server then blocks and waits either for ttl to expire or response to come from broker
if ttl expires 503 is returned to client
if response comes back it is converted to http response and sent back to client.

Broker receives http request event from http server.
Event will either have no context which indicates it should match a release or have the deployment and environment set.
If environment or deployment is set without the other the request is rejected.
Based on the context a matcher for the specified deployment or for all released components is used. These are built by inspecting the deployed and released components and looking up their routes in the registration stored in the NATS.
If request does not match any routes a not found error is returned.
If matched the event target is updated with the matched component's name, commit, and matched route id.
broker checks if a matching component is subscribed locally via grpc and if so sends the event to that component.
otherwise the event is publish onto the component group's NATS subject so that another broker with a subscription for that component can process it.
ttl is updated before sending

Event is received by grpc server for an existing subscription.
grpc server verifies the event source matches the subscribed component, if it does not the broker drops the event and closes the subscription.
The grpc server passes the event to the broker for routing.

The event should already have context set as it is not a genesis event, if it doesn't it is rejected and dropped.
The event source should be complete with component name, commit, and id
The event target should either contain only the component's name or be complete.
Either is not true event is dropped
If only target name is set then event is matched based on context and target commit and route id are added
If event is not matched it is dropped (currently there is no response sent to component)
the deployment or release are then pulled and broker verifies both the source and target components are part of the deployment spec.
if they are not event is dropped.
broker checks if a matching component is subscribed locally via grpc and if so sends the event to that component.
otherwise the event is publish onto the component's NATS subject so that another broker with a subscription for that component can process it.
ttl is updated before sending

Workflow is same as for grpc but target should have both name and commit set.
If there is matching component it means that the component got unsubscribed while process the event, otherwise the broker would not have been listening on the subject. Is this case the event is republished onto the same subject.