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[#1551] Handle external exits of processes #1514

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[#1551] Handle external exits of processes #1514

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16 changes: 16 additions & 0 deletions src/cowboy_stream_h.erl
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Original file line number Diff line number Diff line change
Expand Up @@ -154,6 +154,22 @@ info(StreamID, Exit={'EXIT', Pid, {Reason, Stacktrace}}, State=#state{ref=Ref, p
do_info(StreamID, Exit, [
{error_response, 500, #{<<"content-length">> => <<"0">>}, <<>>}
|Commands], State);
info(StreamID, Exit={'EXIT', Pid, Reason}, State=#state{ref=Ref, pid=Pid}) ->
Commands0 = [{internal_error, Exit, 'Stream process crashed.'}],
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Let's use exited rather than crashed.

Commands = case Reason of
normal -> Commands0;
shutdown -> Commands0;
{shutdown, _} -> Commands0;
_ -> [{log, error,
"Ranch listener ~p, connection process ~p, stream ~p "
"had its request process ~p exit with reason "
"~999999p~n",
[Ref, self(), StreamID, Pid, Reason]}
|Commands0]
end,
do_info(StreamID, Exit, [
{error_response, 500, #{<<"content-length">> => <<"0">>}, <<>>}
|Commands], State);
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You can probably extract all this into a separate function, with slightly different behavior depending on the presence of a stacktrace (use undefined for the exit case).

%% Request body, auto mode, no body buffered.
info(StreamID, Info={read_body, Pid, Ref, auto, infinity}, State=#state{read_body_buffer= <<>>}) ->
do_info(StreamID, Info, [], State#state{
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8 changes: 7 additions & 1 deletion test/handlers/crash_h.erl
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Expand Up @@ -13,4 +13,10 @@ init(_, no_reply) ->
init(Req, reply) ->
_ = cowboy_req:reply(200, Req),
ct_helper:ignore(?MODULE, init, 2),
error(crash).
error(crash);
init(_, internal_exit) ->
ct_helper:ignore(?MODULE, init, 2),
exit(internal_exit);
init(_, external_exit) ->
ct_helper:ignore(?MODULE, init, 2),
exit(self(), external_exit).
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The ignore function is about crashes not exits. This handler is about crashes as well. I don't think this belongs here. A better place for this test would be in stream_handler_SUITE similar to this test https://github.com/ninenines/cowboy/blob/master/test/stream_handler_SUITE.erl#L341-L362 (just get the pid and exit the process immediately, the test shouldn't be that long). It's OK to only test exit/2 in this case.

117 changes: 117 additions & 0 deletions test/metrics_SUITE.erl
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Expand Up @@ -76,6 +76,8 @@ init_routes(_) -> [
{"/", hello_h, []},
{"/crash/no_reply", crash_h, no_reply},
{"/crash/reply", crash_h, reply},
{"/crash/internal_exit", crash_h, internal_exit},
{"/crash/external_exit", crash_h, external_exit},
{"/default", default_h, []},
{"/full/:key", echo_h, []},
{"/resp/:key[/:arg]", resp_h, []},
Expand Down Expand Up @@ -542,3 +544,118 @@ error_response_after_reply(Config) ->
%% All good!
gun:close(ConnPid)
end.

error_response_after_internal_exit(Config) ->
doc("Confirm metrics are correct when an error_response command is returned "
"after internal exit."),
%% Perform a GET request.
ConnPid = gun_open(Config),
Ref = gun:get(ConnPid, "/crash/internal_exit", [
{<<"accept-encoding">>, <<"gzip">>},
{<<"x-test-pid">>, pid_to_list(self())}
]),
{response, fin, 500, RespHeaders} = gun:await(ConnPid, Ref, infinity),
timer:sleep(100),
%% Receive the metrics and validate them.
receive
{metrics, From, Metrics} ->
%% Ensure the timestamps are in the expected order.
#{
req_start := ReqStart, req_end := ReqEnd,
resp_start := RespStart, resp_end := RespEnd
} = Metrics,
true = (ReqStart =< RespStart)
and (RespStart =< RespEnd)
and (RespEnd =< ReqEnd),
%% We didn't send a body.
#{
req_body_start := undefined,
req_body_end := undefined,
req_body_length := 0
} = Metrics,
%% We got a 500 response without a body.
#{
resp_status := 500,
resp_headers := ExpectedRespHeaders,
resp_body_length := 0
} = Metrics,
ExpectedRespHeaders = maps:from_list(RespHeaders),
%% The request process executed normally.
#{procs := Procs} = Metrics,
[{_, #{
spawn := ProcSpawn,
exit := ProcExit,
reason := {internal_exit, _StackTrace}
}}] = maps:to_list(Procs),
true = ProcSpawn =< ProcExit,
%% Confirm other metadata are as expected.
#{
ref := _,
pid := From,
streamid := 1,
reason := {internal_error, {'EXIT', _Pid, {internal_exit, _StackTrace}}, 'Stream process crashed.'},
req := #{},
informational := [],
user_data := #{}
} = Metrics,
%% All good!
gun:close(ConnPid)
end.

error_response_after_external_exit(Config) ->
doc("Confirm metrics are correct when an error_response command is returned "
"after external exit."),
%% Perform a GET request.
ConnPid = gun_open(Config),
Ref = gun:get(ConnPid, "/crash/external_exit", [
{<<"accept-encoding">>, <<"gzip">>},
{<<"x-test-pid">>, pid_to_list(self())}
]),
{response, fin, 500, RespHeaders} = gun:await(ConnPid, Ref, infinity),
timer:sleep(100),
%% Receive the metrics and validate them.
receive
{metrics, From, Metrics} ->
%% Ensure the timestamps are in the expected order.
#{
req_start := ReqStart, req_end := ReqEnd,
resp_start := RespStart, resp_end := RespEnd
} = Metrics,
true = (ReqStart =< RespStart)
and (RespStart =< RespEnd)
and (RespEnd =< ReqEnd),
%% We didn't send a body.
#{
req_body_start := undefined,
req_body_end := undefined,
req_body_length := 0
} = Metrics,
%% We got a 500 response without a body.
#{
resp_status := 500,
resp_headers := ExpectedRespHeaders,
resp_body_length := 0
} = Metrics,
ExpectedRespHeaders = maps:from_list(RespHeaders),
%% The request process executed normally.
#{procs := Procs} = Metrics,
[{_, #{
spawn := ProcSpawn,
exit := ProcExit,
reason := external_exit
}}] = maps:to_list(Procs),
true = ProcSpawn =< ProcExit,
%% Confirm other metadata are as expected.
#{
ref := _,
pid := From,
streamid := 1,
reason := {internal_error, {'EXIT', _Pid, external_exit}, 'Stream process crashed.'},
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That said, checking this still seems valuable. So I would leave this test. I would just do the exit from the test case instead.

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alright makes sense. On it.

req := #{},
informational := [],
user_data := #{}
} = Metrics,
%% All good!
gun:close(ConnPid)
end.