[erlang-questions] Need help with simple_one_for_one
Mazen Harake
mazen@REDACTED
Wed Aug 20 19:00:51 CEST 2008
Hi Matt,
Sorry this might be a stupid question but did you send it an event?
/Mazen
Matt Williamson wrote:
> I hate to keep bugging with simple problems, but I'm stuck again. My
> FSM dosn't seem to be executing its first state. Here is my init function:
>
> /init(StartArgs) ->
> InitialState = case StartArgs of
> {store_chunk, Chunk} ->
> io:format("FSM Storing chunk...~n"),
> {ok, storing_chunk, [Chunk]};
> {get_chunk, Args} ->
> {ok, getting_chunk, Args};
> Else ->
> %% @todo Add error logging here.
> io:format("Bad arg for FSM: ~p~n", [StartArgs])
> end,
> io:format("FSM Initial State: ~p~n", [InitialState]),
> InitialState./
>
> storing_chunk/2 is exported and I'm not getting any errors. Here is
> that function:
>
> /storing_chunk(_Event, [Chunk]) ->
> io:format("STATE: storing_chunk~n"),
> case erlfs_store_lib:store_chunk() of
> ok ->
> {next_state, notifying_tracker, Chunk};
> {error, Reason} ->
> %% @todo Add error logging here.
> io:format("FSM Stopped: ~p~n", [Reason]),
> {stop, {file, Reason}, Chunk#chunk.chunk_meta}
> end./
>
> On Wed, Aug 20, 2008 at 11:04 AM, Serge Aleynikov <saleyn@REDACTED
> <mailto:saleyn@REDACTED>> wrote:
>
> The error you reported earlier:
>
> {'EXIT', {badarg, [{erlang, apply,
> [erlfs_store_worker_fsm, start_link, {store_chunk, ...}]}]}}
>
> was a clear indication that erlang:apply(M,F,A) was called with A
> being a tuple rather than a list. If this still doesn't work
> after replacing tuple with a list in the second argument of the
> supervisor:start_child/2 call, this means that you probably have
> other issues in the erlfs_store_worker_fsm:start_link/1 itself.
>
> I can't say anything more without seeing a more detailed error report.
>
> Serge
>
>
> Matt Williamson wrote:
>
> Yes, I saw that in the docs. What I was saying is that calling
> apply(M, F,
> A++List) =:= apply(M, F, List) when A =:= [].
>
> I did try your suggestion anyway with the same results.
>
> On Wed, Aug 20, 2008 at 9:54 AM, Serge Aleynikov
> <saleyn@REDACTED <mailto:saleyn@REDACTED>> wrote:
>
> What is the arity of erlfs_store_worker_fsm:start_link
> function?
>
> Not quite sure what you mean by [] ++ 1 below.
>
> The supervisor:start_child/2 takes a list [term()] as the
> second parameter.
> Here's its docs:
>
> "If the case of a simple_one_for_one supervisor, the child
> specification
> defined in Module:init/1 will be used and ChildSpec should
> instead be an
> arbitrary list of terms List. The child process will then
> be started by
> appending List to the existing start function arguments,
> i.e. by calling
> apply(M, F, A++List) where {M,F,A} is the start function
> defined in the
> child specification."
>
> Note the A++List part.
>
>
> Matt Williamson wrote:
>
> I'm afraid that did not work. I am passing an empty
> list, and if I execute
> [] ++ 1 in the shell I get 1.
>
> On Wed, Aug 20, 2008 at 9:31 AM, Serge Aleynikov
> <saleyn@REDACTED <mailto:saleyn@REDACTED>>
> wrote:
>
> Try starting it as:
>
> supervisor:start_child(erlfs_store_worker_sup,
> [{store_chunk, Chunk}])
>
> The simple_one_for_one strategy appends the
> arguments passed to
> supervisor:start_child/2 to the list of args
> specified in the
> supervisor's
> spec.
>
> Serge
>
> Matt Williamson wrote:
>
> Hello,
>
> I am starting a gen_fsm with
> supervisor:start_child(erlfs_store_worker_sup,
> {store_chunk, Chunk}) but I get the following
> error:
>
> {error,
> {'EXIT',
> {badarg,
> [{erlang,
> apply,
>
> [erlfs_store_worker_fsm,
> start_link,
> {store_chunk,
> {chunk,
>
> {chunk_meta,
>
> {file_meta,
>
> "test123",
>
> "test.txt",
> 0,
>
> "text/plain",
>
> {{0,1,1},{0,0,0}}},
> 0,
> 0,
> []},
>
> <<"Hello world!">>}}]},
>
> {supervisor,do_start_child_i,3},
>
> {supervisor,handle_call,3},
>
> {gen_server,handle_msg,6},
>
> {proc_lib,init_p,5}]}}}
>
> I've been trying to figure it out for a while,
> but I am having a hard
> time.
> Here is the Child Spec in the supervisor
> (erlfs_store_worker_sup):
>
> init(Args) ->
> WorkerSpec = {erlfs_store_worker_fsm,
> {erlfs_store_worker_fsm,
> start_link, []},
> temporary, 2000, worker,
> [erlfs_store_worker_fsm]},
> {ok,{{simple_one_for_one, 0, 1}, [WorkerSpec]}}.
>
>
>
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--
Mazen Harake <mazen@REDACTED>
Erlang Software Developer and Consultant,
Erlang Training & Consulting, Ltd
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