Fix mistakes in handle_down_worker for exercise 23.3

Author: Stratus3D

chapter_23/exercise_3/src/prime_tester_load_balancer.erl

@@ -22,8 +22,7 @@
 
 -define(SERVER, ?MODULE).
 
--record(state,{limit=0,
-free_pids=[],
+-record(state,{free_pids=[],
 jobs=#{},
 queue=queue:new()}).
 
@@ -128,16 +127,24 @@ code_change(_OldVsn, State, _Extra) ->
 %%% Internal functions
 %%%===================================================================
 
-handle_down_worker(Pid, State=#state{limit=Limit, jobs=Pids, queue=Queue}) ->
-io:format("got worker down"),
+handle_down_worker(Pid, State=#state{free_pids=FreePids, jobs=Jobs, queue=Queue}) ->
+io:format("Got worker down. Sending error back to caller~n"),
+% Send error back to the caller
+{From, Number} =maps:get(Pid, Jobs),
+gen_server:reply(From,{error,{failed_to_check, Number}}),
+
+% Start a new worker in its place
+{ok, NewPid} =supervisor:start_child(prime_tester_worker_sup, []),
+_Ref=erlang:monitor(process, NewPid),
+
 casequeue:out(Queue) of
 {{value,{From, Number}}, NewQueue} ->
-{ok, Pid} =supervisor:start_child(prime_tester_worker_sup, [Number]),
-NewPid=erlang:monitor(process, Pid),
-NewPids=gb_sets:insert(NewPid, maps:remove(Pid,Pids)),
-gen_server:reply(From,{ok, Pid}),
-{noreply, State#state{jobs=NewPids, queue=NewQueue}};
+% Start the new job
+ok=prime_tester_worker:is_prime(NewPid, Number),
+NewJobs=maps:put(NewPid, {From, Number}, maps:remove(Pid,Jobs)),
+
+{noreply, State#state{jobs=NewJobs, queue=NewQueue}};
 {empty, _} ->
 % If nothing in the queue continue as before
-{noreply, State#state{limit=Limit+1, jobs=gb_sets:delete(Pid, Pids)}}
+{noreply, State#state{free_pids=[NewPid|FreePids], jobs=maps:remove(Pid, Jobs)}}
 end.