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POerlang OTP Supervisor crashing
 

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    <p>I'm working through the Erlang documentation, trying to understand the basics of setting up an OTP gen_server and supervisor. Whenever my gen_server crashes, my supervisor crashes as well. In fact, whenever I have an error on the command line, my supervisor crashes. </p> <p>I expect the gen_server to be restarted when it crashes. I expect command line errors to have <em>no bearing whatsoever</em> on my server components. My supervisor shouldn't be crashing at all.</p> <p>The code I'm working with is a basic "echo server" that replies with whatever you send in, and a supervisor that will restart the echo_server 5 times per minute at most (one_for_one). My code:</p> <p><strong>echo_server.erl</strong></p> <pre><code>-module(echo_server). -behaviour(gen_server). -export([start_link/0]). -export([echo/1, crash/0]). -export([init/1, handle_call/3, handle_cast/2]). start_link() -&gt; gen_server:start_link({local, echo_server}, echo_server, [], []). %% public api echo(Text) -&gt; gen_server:call(echo_server, {echo, Text}). crash() -&gt; gen_server:call(echo_server, crash).. %% behaviours init(_Args) -&gt; {ok, none}. handle_call(crash, _From, State) -&gt; X=1, {reply, X=2, State}. handle_call({echo, Text}, _From, State) -&gt; {reply, Text, State}. handle_cast(_, State) -&gt; {noreply, State}. </code></pre> <p><strong>echo_sup.erl</strong></p> <pre><code>-module(echo_sup). -behaviour(supervisor). -export([start_link/0]). -export([init/1]). start_link() -&gt; supervisor:start_link(echo_sup, []). init(_Args) -&gt; {ok, {{one_for_one, 5, 60}, [{echo_server, {echo_server, start_link, []}, permanent, brutal_kill, worker, [echo_server]}]}}. </code></pre> <p>Compiled using <code>erlc *.erl</code>, and here's a sample run:</p> <pre><code>Erlang R13B01 (erts-5.7.2) [source] [smp:2:2] [rq:2] [async-threads:0] [kernel-p oll:false] Eshell V5.7.2 (abort with ^G) 1&gt; echo_sup:start_link(). {ok,&lt;0.37.0&gt;} 2&gt; echo_server:echo("hi"). "hi" 3&gt; echo_server:crash(). =ERROR REPORT==== 5-May-2010::10:05:54 === ** Generic server echo_server terminating ** Last message in was crash ** When Server state == none ** Reason for termination == ** {'function not exported', [{echo_server,terminate, [{{badmatch,2}, [{echo_server,handle_call,3}, {gen_server,handle_msg,5}, {proc_lib,init_p_do_apply,3}]}, none]}, {gen_server,terminate,6}, {proc_lib,init_p_do_apply,3}]} =ERROR REPORT==== 5-May-2010::10:05:54 === ** Generic server &lt;0.37.0&gt; terminating ** Last message in was {'EXIT',&lt;0.35.0&gt;, {{{undef, [{echo_server,terminate, [{{badmatch,2}, [{echo_server,handle_call,3}, {gen_server,handle_msg,5}, {proc_lib,init_p_do_apply,3}]}, none]}, {gen_server,terminate,6}, {proc_lib,init_p_do_apply,3}]}, {gen_server,call,[echo_server,crash]}}, [{gen_server,call,2}, {erl_eval,do_apply,5}, {shell,exprs,6}, {shell,eval_exprs,6}, {shell,eval_loop,3}]}} ** When Server state == {state, {&lt;0.37.0&gt;,echo_sup}, one_for_one, [{child,&lt;0.41.0&gt;,echo_server, {echo_server,start_link,[]}, permanent,brutal_kill,worker, [echo_server]}], {dict,0,16,16,8,80,48, {[],[],[],[],[],[],[],[],[],[],[],[],[],[],[], []}, {{[],[],[],[],[],[],[],[],[],[],[],[],[],[], [],[]}}}, 5,60, [{1273,79154,701110}], echo_sup,[]} ** Reason for termination == ** {{{undef,[{echo_server,terminate, [{{badmatch,2}, [{echo_server,handle_call,3}, {gen_server,handle_msg,5}, {proc_lib,init_p_do_apply,3}]}, none]}, {gen_server,terminate,6}, {proc_lib,init_p_do_apply,3}]}, {gen_server,call,[echo_server,crash]}}, [{gen_server,call,2}, {erl_eval,do_apply,5}, {shell,exprs,6}, {shell,eval_exprs,6}, {shell,eval_loop,3}]} ** exception exit: {{undef, [{echo_server,terminate, [{{badmatch,2}, [{echo_server,handle_call,3}, {gen_server,handle_msg,5}, {proc_lib,init_p_do_apply,3}]}, none]}, {gen_server,terminate,6}, {proc_lib,init_p_do_apply,3}]}, {gen_server,call,[echo_server,crash]}} in function gen_server:call/2 4&gt; echo_server:echo("hi"). ** exception exit: {noproc,{gen_server,call,[echo_server,{echo,"hi"}]}} in function gen_server:call/2 5&gt; </code></pre>
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