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I am stuck in a bit of a fix trying to run gen_server on another node. So I have a common gen_server class which looks like this
start(FileName) ->
start_link(node(), FileName).
start_link(ThisNode, FileName) ->
gen_server:start_link({local, ?MODULE}, ?MODULE, [ThisNode, FileName], []).
init([ThisNode, FileName]) ->
process_flag(trap_exit, true),
{ok, Terms} = file:consult(FileName),
{A1, B1, C1} = lists:nth(1,Terms),
place_objects(A1, B1, C1).
Now I want to start multiple nodes that will run the same gen_server and somehow communicate with each other, and use a another node to orchestrate that. (All these nodes are started on my local terminal).
So I start a new node in one terminal using erl -sname bar where I intend to run the gen_server, and compile the gen_server module on this node. Then I start another node called 'sup' which I intend to use as a coordinator for all the other nodes. If I run the command my_gen_server:start("config_bar.txt"). on bar, it successfully returns but when I run the command rpc:call('bar#My-MacBook-Pro', my_gen_server, start, ["config_bar.txt"]). on sup, it successfully returns from the init method (I checked this by putting in the logs) but immediately after that, I get this error:
{ok,<9098.166.0>}
(sup#My-MacBook-Pro)2> =ERROR REPORT==== 21-Feb-2022::11:12:30.443051 ===
** Generic server my_gen_server terminating
** Last message in was {'EXIT',<9098.165.0>,
{#Ref<0.3564861827.2990800899.137513>,return,
{ok,<9098.166.0>}}}
** When Server state == {10,10,#Ref<9098.1313723616.3973185546.82660>,
'bar#My-MacBook-Pro'}
** Reason for termination ==
** {#Ref<0.3564861827.2990800899.137513>,return,{ok,<9098.166.0>}}
=CRASH REPORT==== 21-Feb-2022::11:12:30.443074 ===
crasher:
initial call: my_gen_server:init/1
pid: <9098.166.0>
registered_name: my_gen_server
exception exit: {#Ref<0.3564861827.2990800899.137513>,return,
{ok,<9098.166.0>}}
in function gen_server:decode_msg/9 (gen_server.erl, line 481)
ancestors: [<9098.165.0>]
message_queue_len: 0
messages: []
links: []
dictionary: []
trap_exit: true
status: running
heap_size: 1598
stack_size: 29
reductions: 3483
neighbours:
I can't seem to figure out what causes the error and if there's anything I need to add to my gen_server code to fix it. Would really appreciate some help on this one!
The gen_server in the remote node is linked to an ephemeral process created for the rpc call.
As this ephemeral process exits with a term that's different from normal (the actual result of the rpc call), the exit signal propagates to the gen_server, killing it.
You can use gen_server:start instead of gen_server:start_link or, if you want the gen_server to be part of the supervission tree, instruct its supervisor to spawn it:
rpc:call('bar#My-MacBook-Pro', my_gen_sup, start_child, ["config_bar.txt"]).
I have a yaws runmod defined in yaws.conf as:
runmod = sg_app
the module contains an exported function:
start()->
io:format("~p start~n", [ sg_sup:start_link() ]).
When I start yaws I see a call to the runmod:
=INFO REPORT==== 29-Oct-2015::16:46:51 === sync call sg_app:start
{ok,<0.61.0>} start
But the supervisor is nonexistent:
1> whereis(sg_sup).
undefined
If I call the runmod:start manually, the supervisor hangs around.
2> sg_app:start().
{ok,<0.73.0>} start
ok
3> whereis(sg_sup).
<0.73.0>
What have I done wrong?
Your runmod's start/0 function is starting the supervisor with start_link/0, which means it's getting linked to the parent process. When that process dies, it takes your runmod process down with it, due to the link. The runmod feature isn't designed for starting a supervision tree.
You might instead consider using a yapp, which allows your code to run as a regular Erlang application in the same Erlang node as Yaws and be registered to have Yaws dispatch requests into it.
Another option is to launch your application using a separately spawned, infinite process:
start()->
spawn(fun () ->
application:start(my_app, permanent),
receive after infinity -> ok end
end).
I am going through the riak-erlang-client https://github.com/basho/riak-erlang-client. As i am following the steps, i am facing error at storing the data.
I did the following:
2> {ok,Pid} = riakc_pb_socket:start_link("127.0.0.1",8087).
{ok,<0.35.0>}
3>
3>
3> riakc_pb_socket:ping(Pid).
pong
4> Val = 1.
1
7> Obj = riakc_obj:new(<<"Bucket">>,<<"one">>,Val).
{riakc_obj,<<"Bucket">>,<<"one">>,undefined,[],undefined,1}
everything was working here as per the documents, but when i am trying to store the data with the following command.
8> riakc_pb_socket:put(Pid,Obj).
After this command i am getting the following error,
=ERROR REPORT==== 13-May-2014::18:15:46 ===
** Generic server <0.35.0> terminating
** Last message in was {req_timeout,#Ref<0.0.0.60>}
** When Server state == {state,"127.0.0.1",8087,false,false,undefined,false,
gen_tcp,undefined,
{[],[]},
1,[],infinity,undefined,undefined,undefined,
undefined,[],100}
** Reason for termination ==
** disconnected
** exception exit: disconnected
where i am doing wrong, please suggest me.
That error means that your TCP request timed out for some reason. Is there anything in Riak's error.log or console.log files that could tell you why?
Can you test to see if your Riak node is running by going to http:127.0.0.1:8098/ping in a browser?
If it's up and running you can try your test again by either clearing your currently bound variables with f(). (or opening a new Erlang REPL), and retrying the commands.
I am having trouble starting the cowboy application it is giving me following error. For some reason the ranch is not starting, although I have added code to start the ranch in my application.
I see a new git repo cowlib being pulled. but still having trouble.
1> application:start(satomi).
{error,
{bad_return,
{{satomi_app,start,[normal,[]]},
{'EXIT',
{noproc,
{gen_server,call,
[ranch_sup,
{start_child,
{{ranch_listener_sup,http},
{ranch_listener_sup,start_link,
[http,100,ranch_tcp,
[{port,9090}],
cowboy_protocol,
[{...}]]},
permanent,5000,supervisor,
[ranch_listener_sup]}},
infinity]}}}}}}
=INFO REPORT==== 12-Sep-2013::11:42:46 ===
application: satomi
exited: {bad_return,
{{satomi_app,start,[normal,[]]},
{'EXIT',
{noproc,
{gen_server,call,
[ranch_sup,
{start_child,
{{ranch_listener_sup,http},
{ranch_listener_sup,start_link,
[http,100,ranch_tcp,
[{port,9090}],
cowboy_protocol,
[{env,
[{dispatch,
[{'_',[],[{[],[],toppage_handler,[]}]}]}]}]]},
permanent,5000,supervisor,
[ranch_listener_sup]}},
infinity]}}}}}
type: temporary
Following is my app.src
>cat satomi.app.src
{application, satomi,
[
{description, ""},
{vsn, "1"},
{registered, []},
{applications, [
kernel,
stdlib,
cowboy
]},
{mod, { satomi_app, []}},
{env, []}
]}.
>cat satomi.erl
-module(satomi).
-export([start/0]).
start()->
ok = application:start(crypto),
ok = application:start(sasl),
ok = application:start(ranch),
ok = application:start(cowlib),
ok = application:start(cowboy),
ok = application:start(satomi).
I am trying to figure out what's going wrong here
Can anyone point me to the working sample of cowboy that I can use as a template. I am using rebar to compile the code. I don't think that should make any difference.
I am using following command to start the application
erl -pa ./ebin ./deps/*/ebin
When calling application:start(satomi) from the shell it doesn't automatically start the applications it depends on, those need to be started manually.
The satomi:start/0 function you have does exactly this, so the solution is to call satomi:start() from the shell.
The reason is that application:start(satomi) will actually not call satomi:start(), it is a convenience method for starting the application and its dependencies when the application is not part of an Erlang release.
UPDATE: Since Erlang R16B02, there is also application:ensure_all_started. It starts all the dependencies automatically.
I wrote a simple application in Erlang, but it refuses to work with the following error:
=SUPERVISOR REPORT==== 18-Jan-2012::15:03:27 ===
Supervisor: {<0.60.0>,my_sup}
Context: start_error
Reason: {'EXIT',{undef,[{my,start,[{8077,none}]},
{supervisor,do_start_child,2},
{supervisor,start_children,3},
{supervisor,init_children,2},
{gen_server,init_it,6},
{proc_lib,init_p_do_apply,3}]}}
Offender: [{pid,undefined},
{name,my},
{mfa,{my,start,[{8077,none}]}},
{restart_type,permanent},
{shutdown,brutal_kill},
{child_type,worker}]
=INFO REPORT==== 18-Jan-2012::15:03:27 ===
application: my
exited: {shutdown,{my_app,start,[normal,[noarg]]}}
type: temporary {error,{shutdown,{my_app,start,[normal,[noarg]]}}}
And the modules:
my.erl
-module(my).
-export([start/2, stop/0]).
start(Port,_arg) ->
io:format("starting my").
stop() ->
ok.
my_app.erl Application module, perform application behavior.
-module(my_app).
-behaviour(application).
-export([start/2, stop/1]).
start(_Type, _Args) ->
io:format("my server starting~n"),
my_sup:start_link().
stop(_State) ->
io:format("my server terminating~n"),
ok.
my_sup.erl Supervisor logic
-module(my_sup).
-behaviour(supervisor).
-export([start_link/0]).
-export([init/1]).
start_link() ->
supervisor:start_link(my_sup, []).
init(_Args) ->
{ok, {
{one_for_one, 10, 60},
[{my, {my, start, [{8077,none}]
},
permanent, brutal_kill, worker, [my]}]}}.
Config file (my.app):
{application, my,
[
{description, "Demo"},
{vsn, "1.0"},
{id, "hello"},
{modules, [my,my_sup]},
{registered, [my,my_sup]},
{applications, [kernel, stdlib]},
%%
%% mod: Specify the module name to start the application, plus args
%%
{mod, {my_app, [noarg]}},
{env, []}
]
}.
I changed child spec like you recommend, but the problem still remains.
=SUPERVISOR REPORT==== 19-Jan-2012::00:34:21 ===
Supervisor: {<0.96.0>,my_sup}
Context: start_error
Reason: <0.97.0>
Offender: [{pid,undefined},
{name,my},
{mfa,{my,start,[8077,none]}},
{restart_type,permanent},
{shutdown,brutal_kill},
{child_type,worker}]
=ERROR REPORT==== 19-Jan-2012::00:34:21 ===
Error in process <0.97.0> with exit value:
{{badmatch,{error,eaddrinuse}},[{my,'- start/2-fun-0-',1}]}
=INFO REPORT==== 19-Jan-2012::00:34:21 ===
application: my
exited: {shutdown,{my_app,start,[normal,[noarg]]}}
type: temporary
{error,{shutdown,{my_app,start,[normal,[noarg]]}}}
The my:start/2 should take two arguments but in the child specification you only give it one argument ({8077,none}). You could change the child spec to:
{my, {my, start, [8077,none]}, permanent, brutal_kill, worker, [my]}
As an aside your indentation and line breaking of the Supervisor Specification is a bit off making it difficult to see what belongs to what.
EDIT: Comment to new error
This is not the same problem as before. You are getting a new error, eaddrinuse, which normally means you are trying to use an IP address/port which is already in use. This would imply you are doing some socket programming in your code.
Your supervisor specifies that my:start should take one argument, but it takes two. You probably want to change the child spec to:
{one_for_one, 10, 60},[{my, {my, start, [8077,none]}
Your my:start/2 provides a wrong return value.
Supervisor expects tuple {ok,Pid}, while your function simply returns ok (the last call is to io:format, which returns ok, so your function also does).
If you want to use a supervisor, you must spawn a new process and link it to the supervisor. For example
start(_) -> {ok,spawn_link(fun() -> io:format("~w started~n",[self()]),timer:sleep(5000),io:format("~w exiting~n",[self()]) end)}.
should do the job for you.