[erlang-questions] gen_server: {bad_return_value, {error, {91, invalid_string}}}

[Raimo Niskanen]

On Tue, Aug 15, 2017 at 11:09:05AM +0200, Ali Sabil wrote:
> Hi Khitai,
> 
> That's because jiffy (mis)uses erlang:throw.

If it is so that jiffy:decode(Msg) throws {error,{91,invalid_string}}, then
it happens to be one way to return from a callback i.e to throw the value.

So, yes - if so jiffy misuses erlang:throw.  Jiffy should use erlang:error
if it is an error.

/ Raimo


> 
> Best,
> Ali
> 
> On Tue, Aug 15, 2017 at 5:13 AM, Khitai Pang <khitai.pang@REDACTED>
> wrote:
> 
> > Hi Raimo, Attila,
> >
> > I have found out the cause: the handle_info callback of my gen_server
> > failed to decode a json string:
> >
> > {Json} = jiffy:decode(Msg),
> >
> > the above code generates {error, {91, invalid_string}}, and I believe
> > the error is caught by OTP gen_server code, and somehow the terminate()
> > function in OTP gen_server code complains about {bad_return_value,
> > {error, {91, invalid_string}}}.  Now I know the root cause of the
> > problem but I don't understand why it ends up in an error of
> > gen_server:terminate().
> >
> >
> > Best wishes,
> > Khitai
> >
> > On 2017/8/14 19:54, Attila Rajmund Nohl wrote:
> > > Hello!
> > >
> > > I'd check the code that handles the
> > > {basic.cancel_ok,<<"amq.ctag-YRIyK1Kv0i93rkLbD9Zo8w">>} message,
> > > because this was the last received message. Also my intuition is that
> > > somewhere your code expects a list of strings, but gets a simple
> > > string, and when it checks the first element, it finds 91 (probably
> > > the '[' character) instead of a string.
> > >
> > > 2017-08-14 5:17 GMT+02:00 Khitai Pang <khitai.pang@REDACTED>:
> > >> Hi list,
> > >>
> > >> On my CentOS7 server with esl-erlang-19.3.6-1.x86_64, a gen_server
> > >> process mysteriously crashes.  See the error info below.  I can't figure
> > >> out the reason of the error.  Any hint would be appreciated.
> > >>
> > >> {error_report,<0.25443.97>,
> > >>       {<0.28918.97>,crash_report,
> > >>        [[{initial_call,{xeef_analyzer,init,[Argument__1]}},
> > >>          {pid,<0.28918.97>},
> > >>          {registered_name,xeef_analyzer_009},
> > >>          {error_info,
> > >>              {exit,
> > >>                  {bad_return_value,{error,{91,invalid_string}}},
> > >> [{gen_server,terminate,7,[{file,"gen_server.erl"},{line,812}]},
> > >>                   {proc_lib,init_p_do_apply,3,
> > >>                       [{file,"proc_lib.erl"},{line,247}]}]}},
> > >>          {ancestors,[xeef_analyzer_sup,xeef_sup,<0.25310.97>]},
> > >> {messages,[{basic.cancel_ok,<<"amq.ctag-YRIyK1Kv0i93rkLbD9Zo8w">>}]},
> > >>          {links,
> > >> [#Port<0.2317500>,#Port<0.2317503>,<0.29009.97>,#Port<0.2317499>]},
> > >>          {dictionary,
> > >>              [{rand_seed,
> > >>                   {#{max => 18446744073709551615,next =>
> > >> #Fun<rand.4.41921595>,
> > >>                      type => exs1024,uniform => #Fun<rand.5.41921595>,
> > >>                      uniform_n => #Fun<rand.6.41921595>},
> > >>                    {[5529181756040335035,6774320120208346895,
> > >>                      4985297473998268992,12813505499546735856,
> > >>                      3059599059795068553,3134963973831305956,
> > >>                      5508046504858988103,3821329447243874404],
> > >>                     [6547380368325771448,16036002885223559991,
> > >>                      13982350927889545678,14401258729428095242,
> > >>                      6347438184782916914,10561027033563628251,
> > >>                      10847483533189471003,3486622809589930158]}}}]},
> > >>          {trap_exit,true},
> > >>          {status,running},
> > >>          {heap_size,987},
> > >>          {stack_size,27},
> > >>          {reductions,139726}],
> > >>         []]}}
> > >>
> > >>
> > >> {error_report,<0.25443.97>,
> > >>       {<0.29009.97>,supervisor_report,
> > >>        [{supervisor,{local,xeef_analyzer_sup}},
> > >>         {errorContext,child_terminated},
> > >>         {reason,{bad_return_value,{error,{91,invalid_string}}}},
> > >>         {offender,
> > >>             [{pid,<0.28918.97>},
> > >>              {id,xeef_analyzer},
> > >>              {mfargs,
> > >>                  {xeef_analyzer,start_link,
> > >> [{sandbox,{<0.28962.97>,<<"sanbox_queue">>},none,true}]}},
> > >>              {restart_type,permanent},
> > >>              {shutdown,5000},
> > >>              {child_type,worker}]}]}}
> > >>
> > >>
> > >>
> > >> Best wishes,
> > >> Khitai
> > >> _______________________________________________
> > >> erlang-questions mailing list
> > >> erlang-questions@REDACTED
> > >> http://erlang.org/mailman/listinfo/erlang-questions
> >
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> >

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-- 

/ Raimo Niskanen, Erlang/OTP, Ericsson AB