OK no time for a full blow, polished blog post; When using gen_fsm I realized that often I want some sort of queueing. Two reasons promote this: to reduce the complexity caused by {States} x {Events} to implement some kind of asynchronous command execution processing model I usualle encounter both reasons and I ended up with two useful function that I copy into every gen_fsm I build: deq(State = #state{evtq = []}) -> {next_state, ready, State}; deq(State = #state{evtq = [Msg | T]}) -> ?MODULE:ready(Msg, State#state{evtq = T}). This requires one adds evtq as a field to the #state{} record. The function deq/1 will be used to work of events(one could say commands) until the queue is empty and finally rests in the state ready . This function is called at the point where one would return {next_state, ready, State} So instead of transitioning directly to ready we call the deq function which will process all defered events. On the other hand there is a
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