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diff --git a/_build/static/archives/extend/2013-July/000158.html b/_build/static/archives/extend/2013-July/000158.html new file mode 100644 index 00000000..41d6dd01 --- /dev/null +++ b/_build/static/archives/extend/2013-July/000158.html @@ -0,0 +1,175 @@ +<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"> +<HTML> + <HEAD> + <TITLE> [99s-extend] Cowboy handler linked processes + </TITLE> + <LINK REL="Index" HREF="index.html" > + <LINK REL="made" HREF="mailto:extend%40lists.ninenines.eu?Subject=Re%3A%20%5B99s-extend%5D%20Cowboy%20handler%20linked%20processes&In-Reply-To=%3C51E7C514.5040504%40ninenines.eu%3E"> + <META NAME="robots" CONTENT="index,nofollow"> + <style type="text/css"> + pre { + white-space: pre-wrap; /* css-2.1, curent FF, Opera, Safari */ + } + </style> + <META http-equiv="Content-Type" content="text/html; charset=us-ascii"> + <LINK REL="Previous" HREF="000157.html"> + <LINK REL="Next" HREF="000159.html"> + </HEAD> + <BODY BGCOLOR="#ffffff"> + <H1>[99s-extend] Cowboy handler linked processes</H1> + <B>Loïc Hoguin</B> + <A HREF="mailto:extend%40lists.ninenines.eu?Subject=Re%3A%20%5B99s-extend%5D%20Cowboy%20handler%20linked%20processes&In-Reply-To=%3C51E7C514.5040504%40ninenines.eu%3E" + TITLE="[99s-extend] Cowboy handler linked processes">essen at ninenines.eu + </A><BR> + <I>Thu Jul 18 12:36:04 CEST 2013</I> + <P><UL> + <LI>Previous message: <A HREF="000157.html">[99s-extend] Cowboy handler linked processes +</A></li> + <LI>Next message: <A HREF="000159.html">[99s-extend] Cowboy handler linked processes +</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#158">[ date ]</a> + <a href="thread.html#158">[ thread ]</a> + <a href="subject.html#158">[ subject ]</a> + <a href="author.html#158">[ author ]</a> + </LI> + </UL> + <HR> +<!--beginarticle--> +<PRE>I don't think the problem is that the handler is reused, we don't reuse +them if there's an error. However we do catch errors to print them in +the logs, and then the process stops normally. If you link without +trap_exit you receive a normal exit signal which is ignored and doesn't +kill your process. I suppose we should throw an exit signal when we got +an error, after logging everything, instead of stopping normally. + +On 07/18/2013 12:31 PM, Adrian Roe wrote: +><i> My issue is the other way round. My handler crashes - and terminate +</I>><i> gets called, but the linked process is NOT stopped (unless I stop it in +</I>><i> terminate having stashed any processes I need to stop in the process +</I>><i> dictionary - this is what I'm currently doing, but yuck!) +</I>><i> +</I>><i> . My question is whether it wouldn't be better to no re-use the handler +</I>><i> process that has crashed and replace it so that handler's can use the +</I>><i> canonical erlang way of stopping related processes rather than having to +</I>><i> do it by hand. +</I>><i> +</I>><i> Obviously if the handler does not crash there's no need to kill the +</I>><i> process, so the current efficiency saving works in the "normal" case/ +</I>><i> +</I>><i> -- +</I>><i> Dr Adrian Roe +</I>><i> Director +</I>><i> +</I>><i> On Thursday, 18 July 2013 at 11:20, Loïc Hoguin wrote: +</I>><i> +</I>>><i> I don't know what happens but there's two things I know: +</I>>><i> +</I>>><i> * Handlers don't trap_exit, so if the linked process crashes, they +</I>>><i> crash too +</I>>><i> * If the handler crashes, we close the connection and stop the +</I>>><i> handler; if not this is a bug +</I>>><i> +</I>>><i> After your log message the handler should stop unless there's a bug +</I>>><i> somewhere. +</I>>><i> +</I>>><i> On 07/18/2013 12:15 PM, Adrian Roe wrote: +</I>>>><i> We have been using spawn_linked workers to handle tasks that live for +</I>>>><i> the lifetime of a single HTTP request +</I>>>><i> +</I>>>><i> Although in the cowboy guide it is clear that Cowboy can use "One +</I>>>><i> Process of Many Requests" I am surprised that this is the case even if +</I>>>><i> the handler crashes. For example, our use case is to copy a large file +</I>>>><i> to the server over HTTP where a worker process relays the file contents +</I>>>><i> to long term storage. The worker process is spawn_linked from the HTTP +</I>>>><i> handler and (for our use case) should die if the handler stops. +</I>>>><i> +</I>>>><i> If the client stops the upload (for example by browsing away, or losing +</I>>>><i> connectivity) we correctly receive an error (see sample Lager trace +</I>>>><i> below), but what we are seeing is that spawn_linked processes are NOT +</I>>>><i> being killed. +</I>>>><i> +</I>>>><i> Is this intended behaviour - I accept it makes sense to reuse the +</I>>>><i> processes but should this continue to be the case even if the previous +</I>>>><i> use of the process crashed? If it is intended behaviour I think the +</I>>>><i> docs should highlight this as we've been leaking processes for some time +</I>>>><i> now, but I've always seen it as erlang's job to look after related +</I>>>><i> process trees in the event of error. Our current workaround is to hold +</I>>>><i> a list of linked processes in process storage and then kill them in the +</I>>>><i> terminate handler which is ugly in the extreme!! We don't know the PIDS +</I>>>><i> of the linked processes until it is too late to return State to Cowboy +</I>>>><i> (i.e. we are already in our handle code)... +</I>>>><i> +</I>>>><i> Kind regards +</I>>>><i> +</I>>>><i> Adrian +</I>>>><i> +</I>>>><i> 16:09:32.347 [info] Trailer upload failed with reason +</I>>>><i> {case_clause,{error,closed}} +</I>>>><i> 16:09:32.348 [error] ** Cowboy handler upload_trailer_resource +</I>>>><i> terminating in handle/2 +</I>>>><i> for the reason error:{case_clause,{error,closed}} +</I>>>><i> ** Handler state was {state,undefined,0,undefined,undefined,undefined} +</I>>>><i> ** Request was +</I>>>><i> [{socket,#Port<0.11230>},{transport,ranch_tcp},{connection,keepalive},{pid,<0.1987.0>},{method,<<"POST">>},{version,'HTTP/1.1'},{peer,{{84,92,32,116},64136}},{host,<<"54.225.117.108">>},{host_info,undefined},{port,8000},{path,<<"/upload_trailer">>},{path_info,undef +</I>>>><i> ined},{qs,<<"name=linux-7.4.21.zip&size=54015414">>},{qs_vals,undefined},{bindings,[]},{headers,[{<<"host">>,<<"54.225.117.108:8000">>},{<<"connection">>,<<"keep-alive">>},{<<"content-length">>,<<"54015414">>},{<<"origin">>,<<"<A HREF="http://54.225.117.108:8000">http://54.225.117.108:8000</A>">>},{<<"user-agent">>,<<"M +</I>>>><i> ozilla/5.0 (Macintosh; Intel Mac OS X 10_8_4) AppleWebKit/537.36 (KHTML, +</I>>>><i> like Gecko) Chrome/28.0.1500.71 +</I>>>><i> Safari/537.36">>},{<<"content-type">>,<<>>},{<<"accept">>,<<"*/*">>},{<<"referer">>,<<"<A HREF="http://54.225.117.108:8000/">http://54.225.117.108:8000/</A>">>},{<<"accept-encoding">>,<<"gzip,deflate,sdch">>},{<<"acce +</I>>>><i> pt-language">>,<<"en-US,en;q=0.8">>},{<<"cookie">>,<<"__jwpusr=cbc133d7-1b49-443c-8a13-364660cc93e5; +</I>>>><i> id3as_manager=f4803c004d71dde3b64394f6e6f44faa54970e93">>}]},{p_headers,[{<<"connection">>,[<<"keep-alive">>]}]},{cookies,undefined},{meta,[]},{body_state,waiting},{multipart,unde +</I>>>><i> fined},{buffer,<<>>},{resp_compress,true},{resp_state,waiting},{resp_headers,[]},{resp_body,<<>>},{onresponse,undefined}] +</I>>>><i> ** Stacktrace: +</I>>>><i> [{i_cowboy,stream_body,0,[{file,"src/i_cowboy.erl"},{line,76}]},{upload_trailer_resource,stream_upload_file,4,[{file,"src/endpoints/upload_trailer_resource.erl"},{line,247}]},{upload_trailer_resource,upload_file,1,[{file,"src/endpoints/upload_trailer_resource.erl"} +</I>>>><i> ,{line,237}]},{upload_trailer_resource,head_or_post,1,[{file,"src/endpoints/upload_trailer_resource.erl"},{line,202}]},{upload_trailer_resource,sequence,2,[{file,"src/endpoints/upload_trailer_resource.erl"},{line,106}]},{upload_trailer_resource,process_request,1,[{file,"src/endpo +</I>>>><i> ints/upload_trailer_resource.erl"},{line,212}]},{i_cowboy,do,3,[{file,"src/i_cowboy.erl"},{line,29}]},{cowboy_handler,handler_handle,4,[{file,"src/cowboy_handler.erl"},{line,119}]}] +</I>>>><i> +</I>>>><i> +</I>>>><i> -- +</I>>>><i> Dr Adrian Roe +</I>>>><i> Director +</I>>>><i> +</I>>>><i> +</I>>>><i> +</I>>>><i> _______________________________________________ +</I>>>><i> Extend mailing list +</I>>>><i> <A HREF="https://lists.ninenines.eu/listinfo/extend">Extend at lists.ninenines.eu</A> <mailto:<A HREF="https://lists.ninenines.eu/listinfo/extend">Extend at lists.ninenines.eu</A>> +</I>>>><i> <A HREF="http://lists.ninenines.eu:81/listinfo/extend">http://lists.ninenines.eu:81/listinfo/extend</A> +</I>>><i> +</I>>><i> +</I>>><i> -- +</I>>><i> Loïc Hoguin +</I>>><i> Erlang Cowboy +</I>>><i> Nine Nines +</I>>><i> <A HREF="http://ninenines.eu">http://ninenines.eu</A> +</I>><i> +</I> + +-- +Loïc Hoguin +Erlang Cowboy +Nine Nines +<A HREF="http://ninenines.eu">http://ninenines.eu</A> + +</PRE> + +<!--endarticle--> + <HR> + <P><UL> + <!--threads--> + <LI>Previous message: <A HREF="000157.html">[99s-extend] Cowboy handler linked processes +</A></li> + <LI>Next message: <A HREF="000159.html">[99s-extend] Cowboy handler linked processes +</A></li> + <LI> <B>Messages sorted by:</B> + <a href="date.html#158">[ date ]</a> + <a href="thread.html#158">[ thread ]</a> + <a href="subject.html#158">[ subject ]</a> + <a href="author.html#158">[ author ]</a> + </LI> + </UL> + +<hr> +<a href="https://lists.ninenines.eu/listinfo/extend">More information about the Extend +mailing list</a><br> +</body></html> |