Deal with unavailable functions

Currently, if a function is processing a call and is not available, the client will throw an error. Perhaps the client should retry until it succeeds.

We're avoiding here having a central queue for function calls, but that might be unavoidable if this method doesn't scale.

Start by locating the client call path that raises errors when a function is unavailable, then examine how function availability is reported. Compare retry behavior with the issue's concern about avoiding a central queue and define success and failure cases before implementation. No file or test is named, so repository exploration and maintainer guidance are needed.

Written by the indexing model from the issue text.