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Kafka is still in the picture to handle overload scenarios (see Invoker Activation Queueing Change).

General dependencies between components

Full lifecycle of invocation and container creation

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Edge case: If an action only has a very small amount of containers (less than there are Controllers in the system), we have a problem with the method described above. Since the front-door schedules round-robin or least-connected, it's impossible to decide to which Controller the request needs to go to hit that has a container available.
In this case, the other Controllers (who didn't get a container) act as a proxy and send the request to a Controller that actually has a container (maybe even via HTTP redirect). The ContainerManager decides which Controllers will act as a proxy in this case, since its the instance that distributes the containers.

Edge case diagram

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