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

[Khitai Pang]

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
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