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Remote Procedure Calls (RPCs)

A remote procedure call is where you call a procedure available on the bus. The sequence of events is:

  • You call the RPC, bus.auth.check_password()
  • An autoratitive process for the auth API handles the request and sends the response.
  • You receive the result

Remote Procedure Calls are useful when:

  1. You require information from a service 1
  2. You wish to wait until a remote procedure has completed an action

You can perform an RPC as follows:

support_case =

RPCs do not provide a fire and forget mode of operation. Consider using events if you need this feature.

At most once semantics

Remote procedure calls will be processed at most once. In some situations the call will never be processed, in which case the client will raise a LigutbusTimeout exception.


Whether to use RPCs or events for communication will depend upon your project's particular needs. Some considerations are:

  • RPCs are conceptually simple. You call a procedure and wait for a response. You do not need to store any state locally, you can simply request data on demand (performance considerations aside).
  • RPCs can be fragile. Any errors in the remote service will propagate to the client's service. You should handle these if possible.
  • Their use within a codebase may be non-obvious, leading to poor performance. Lightbus tries to alleviate this somewhat by using the bus.api.method() calling format, making it clear that this is a bus-based operation.

  1. This is also achievable with events. However you will need to listen for the events and likely store the data locally. See the events section for further discussion.