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From Pasi Eronen ...@iki.fi>
Subject Re: CouchDB 1.0.2 errors under load
Date Fri, 25 Feb 2011 22:43:53 GMT
Thanks! I looked at /proc/(pid-of-beam.smp)/fd, and it seems CouchDB
is indeed using a lot of file descriptors, and the number is growing.
I restarted CouchDB (and my batch job), and after 40 minutes, it was
already using 300 fds; an hour later, the figure was 600; half
an hour later, almost 700.

The default "ulimit -n" was 1024, so that adds up to couple of hours.
As a temporary fix I changed the limit to 64K, so it should work fine
for the weekend :-) (but not much longer)

Based on "netstat -an", the fds are TCP connections stuck in CLOSE_WAIT
state. Hmm. It seems CLOSE_WAIT means the client closed the connection
but CouchDB didn't call close() to release the fd? And that's presumably
a bug somewhere in CouchDB, right?

After the initial error message, the log had ~300 almost identical
error messages of the form (with different number after pread_iolist):

[Thu, 24 Feb 2011 19:42:57 GMT] [error] [<0.31510.2>]
Uncaught error in HTTP request: {exit,
                                 {normal,
                                  {gen_server,call,
                                   [<0.288.0>,
                                    {pread_iolist,812881959},
                                    infinity]}}}

Does this give any hints where the bug might be?

If not, I'll see if I can reproduce the bug somehow in more controlled
setting. (I have a hunch that this might involve the use of HTTP
expect/continue or POST requests with chunked transfer encoding,
but let's see....)

Best regards,
Pasi

On Fri, Feb 25, 2011 at 19:01, Paul Davis <paul.joseph.davis@gmail.com> wrote:
> On Fri, Feb 25, 2011 at 4:18 AM, Pasi Eronen <pe@iki.fi> wrote:
>> Hi,
>>
>> I had a big batch job (inserting 10M+ documents and generating views for them)
>> that ran just fine for about 6 hours, but then I got this error:
>>
>> [Thu, 24 Feb 2011 19:42:57 GMT] [error] [<0.276.0>] ** Generic server
>> <0.276.0> terminating
>> ** Last message in was delayed_commit
>> ** When Server state == {db,<0.275.0>,<0.276.0>,nil,<<"1298547642391489">>,
>>                            <0.273.0>,<0.277.0>,
>>                            {db_header,5,739828,0,
>>                                {4778613011,{663866,0}},
>>                                {4778614954,663866},
>>                                nil,0,nil,nil,1000},
>>                            739828,
>>                            {btree,<0.273.0>,
>>                                {4778772755,{663866,0}},
>>                                #Fun<couch_db_updater.7.10053969>,
>>                                #Fun<couch_db_updater.8.35220795>,
>>                                #Fun<couch_btree.5.124754102>,
>>                                #Fun<couch_db_updater.9.107593676>},
>>                            {btree,<0.273.0>,
>>                                {4778774698,663866},
>>                                #Fun<couch_db_updater.10.30996817>,
>>                                #Fun<couch_db_updater.11.96515267>,
>>                                #Fun<couch_btree.5.124754102>,
>>                                #Fun<couch_db_updater.12.117826253>},
>>                            {btree,<0.273.0>,nil,
>>                                #Fun<couch_btree.0.83553141>,
>>                                #Fun<couch_btree.1.30790806>,
>>                                #Fun<couch_btree.2.124754102>,nil},
>>                            739831,<<"foo_replication_tmp">>,
>>                            "/data/foo/couchdb-data/foo_replication_tmp.couch",
>>                            [],[],nil,
>>                            {user_ctx,null,[],undefined},
>>                            #Ref<0.0.1793.256453>,1000,
>>                            [before_header,after_header,on_file_open],
>>                            false}
>> ** Reason for termination ==
>> ** {{badmatch,{error,emfile}},
>>    [{couch_file,sync,1},
>>     {couch_db_updater,commit_data,2},
>>     {couch_db_updater,handle_info,2},
>>     {gen_server,handle_msg,5},
>>     {proc_lib,init_p_do_apply,3}]}
>>
>> (+lot of other messages with the same timestamp -- can send if they're useful)
>>
>> Exactly at this time, the client got HTTP 500 status code; the request
>> was a bulk get (POST /foo_replication_tmp/_all_docs?include_docs=true).
>>
>> Just before this request, the client had made a PUT (updating an existing
>> document) that got 200 status code, but apparently was not successfully
>> committed to the disk (I'm using "delayed_commits=true" - for my app,
>> this is just fine). The client had received the new _rev value, but when
>> it tried updating the same document a minute later, there was a conflict
>> (and it's not possible that somebody else updated this same document).
>>
>> About four hours later, there was a different error ("accept_failed"
>> sounds like some temporary problem with sockets?):
>>
>> [Thu, 24 Feb 2011 23:55:42 GMT] [error] [<0.20693.4>] {error_report,<0.31.0>,
>>              {<0.20693.4>,std_error,
>>               [{application,mochiweb},
>>                "Accept failed error","{error,emfile}"]}}
>>
>> [Thu, 24 Feb 2011 23:55:42 GMT] [error] [<0.20693.4>] {error_report,<0.31.0>,
>>    {<0.20693.4>,crash_report,
>>     [[{initial_call,{mochiweb_socket_server,acceptor_loop,['Argument__1']}},
>>       {pid,<0.20693.4>},
>>       {registered_name,[]},
>>       {error_info,
>>           {exit,
>>               {error,accept_failed},
>>               [{mochiweb_socket_server,acceptor_loop,1},
>>                {proc_lib,init_p_do_apply,3}]}},
>>       {ancestors,
>>           [couch_httpd,couch_secondary_services,couch_server_sup,<0.32.0>]},
>>       {messages,[]},
>>       {links,[<0.106.0>]},
>>       {dictionary,[]},
>>       {trap_exit,false},
>>       {status,running},
>>       {heap_size,233},
>>       {stack_size,24},
>>       {reductions,200}],
>>      []]}}
>>
>> (+lots of other messages within the next couple of minutes)
>>
>> The same error occured once more, about four hours later.
>>
>> I'm quite new to CouchDB, so I'd appreciate any help in interpreting
>> what these error messages mean. (BTW, are these something I should
>> report as bugs in JIRA? I can do that, but I'd like to at least understand
>> which parts of the error messages are actually relevant here :-)
>>
>> I'm running CouchDB 1.0.2 with Erlang R14B on 64-bit RHEL 5.6.
>>
>> Best regards,
>> Pasi
>>
>
> The error you're getting is because CouchDB is running out of
> available file descriptors to use. Try increasing the limit for the
> user running CouchDB.
>

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