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Date: Sun, 18 Mar 2012 20:34:53 +0000
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Subject: Re: {error,emfile} on CouchDB 1.2.x
From: Robert Newson <rnewson@apache.org>
To: dev@couchdb.apache.org
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I'd rather improve the handling in prepare_group/4, I'd hope we could
explicitly enumerate the cases where deleting the view index is a
reasonable response than do it quite this capriciously.

B.


On 18 March 2012 20:28, Randall Leeds <randall.leeds@gmail.com> wrote:
> On Sun, Mar 18, 2012 at 11:08, Stefan K=F6gl <koeglstefan@gmail.com> wrot=
e:
>
>> Hi,
>>
>> Another thing I noticed during my tests of CouchDB 1.2.x. I redirected
>> live traffic to the instance and after a rather short time, requests
>> were failing with the following information in the logs:
>>
>>
>> [Sun, 18 Mar 2012 16:39:24 GMT] [error] [<0.27554.2>]
>> {error_report,<0.31.0>,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0{=
<0.27554.2>,std_error,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
[{application,mochiweb},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0"Accept failed error",
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0"{error,emfile}"]}}
>> [Sun, 18 Mar 2012 16:39:24 GMT] [error] [<0.27554.2>]
>> {error_report,<0.31.0>,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0{<0.27554.2>,crash_re=
port,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 [[{initial_call,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {mochiwe=
b_acceptor,init,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
['Argument__1','Argument__2',
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0'Argument__3']}},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {pid,<0.27554.2>=
},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {registered_name=
,[]},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {error_info,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {exit,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
{error,accept_failed},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
[{mochiweb_acceptor,init,3},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =
=A0{proc_lib,init_p_do_apply,3}]}},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {ancestors,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 [couch_h=
ttpd,couch_secondary_services,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0couch=
_server_sup,<0.32.0>]},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {messages,[]},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {links,[<0.129.0=
>]},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {dictionary,[]},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {trap_exit,false=
},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {status,running}=
,
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {heap_size,233},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {stack_size,24},
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 {reductions,244}=
],
>> =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0[]]}}
>>
>>
>> I think "emfile" means that CouchDB (or mochiweb?) couldn't open any
>> more files / connections. I've set the (hard and soft) nofile limit for
>> user couchdb to 4096, but didn't raise the ERL_MAX_PORTS accordingly.
>> Anyway, as soon as the error occured, CouchDB started writing most of my
>> view files from scratch, rendering the instance unusable.
>>
>> I'd expect CouchDB to fail more gracefully when the maximum number of
>> open files is reached. Is this a bug or expected behaviour?
>>
>
> Looks like a bug. Whenever there's a problem opening a view file,
> couch_view tries to delete it. Clearly, this is not the right course of
> action when the problem is due to emfile.
>
> Here's a patch that I propose might fix it. I'd like to hear from another
> dev on this, or if there's a better way we should bail out.
>
> diff --git a/src/couchdb/couch_view_group.erl
> b/src/couchdb/couch_view_group.erl
> index 97fc512..ab075bd 100644
> --- a/src/couchdb/couch_view_group.erl
> +++ b/src/couchdb/couch_view_group.erl
> @@ -469,6 +469,10 @@ open_index_file(RootDir, DbName, GroupSig) ->
> =A0 =A0 case couch_file:open(FileName) of
> =A0 =A0 {ok, Fd} =A0 =A0 =A0 =A0-> {ok, Fd};
> =A0 =A0 {error, enoent} -> couch_file:open(FileName, [create]);
> + =A0 =A0{error, emfile} ->
> + =A0 =A0 =A0 =A0?LOG_ERROR("Could not open file for view index: max open=
 files
> reached. "
> + =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 =A0 "Raise ERL_MAX_PORTS or system limi=
ts.", []),
> + =A0 =A0 =A0 =A0throw({error, emfile});
> =A0 =A0 Error =A0 =A0 =A0 =A0 =A0 -> Error
> =A0 =A0 end.