Internal oslo.messaging bus for convergence

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Problem description

We need a message bus for the internal worker API of convergence.

Proposed change

Create a new worker service within heat-engine that is dedicated to handling internal messages to the ‘worker’ (a.k.a. ‘converger’) actor in convergence. Messages on this bus will use the ‘cast’ rather than ‘call’ method to anycast the message to an engine that will handle it asynchronously. We won’t wait for or expect replies from these messages.

The message types that will eventually be implemented on this bus are those marked with the @asynchronous decorator in


We could have a separate heat-worker daemon, but there appears to be no point in making life difficult for deployers as heat-engine can handle the same tasks.

We could mix this into the same service as the existing RPC API that is called by heat-api, but this is messy because the two have entirely different uses. There is already precedent for running another RPC service inside heat-engine, although we can’t reuse that because it listens on a queue specific to the engine id.



Primary assignee:



Target Milestone for completion:


Work Items

  • Implement the new worker service in the engine

  • Implement a client API to make it easy to send messages to the worker service