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From CGS <cgsmcml...@gmail.com>
Subject Re: timeout hitting a database url after launching compaction
Date Mon, 17 Oct 2011 08:24:16 GMT
I am not developer, but it's quite logic, I may say. Once you started 
the compaction, your CouchDB is not responsive while the database is 
preparing for compaction. Triggering immediately GET, the web instance 
responds with status code 500 (internal server error, meaning 
unresponsive server in this case). So, nothing unusual in my opinion.

Cheers,
CGS




On 10/17/2011 09:57 AM, Paolo Negri wrote:
> IO activity is not monitored, there's only one db on the couchdb
> instance and the described job is the only activity executed on this
> machine.
> Delaying the first request on the database url by 30 seconds did
> actually prevent the problem from happening again.
> So the issue seems to happen specifically at the moment right after
> compaction is started.
> The database is about 7GB big once compressed, the server is hosted on
> ec2 with the database directory placed on his own dedicated ephemeral
> storage.
>
> Thanks,
>
> Paolo
>
> On Fri, Oct 14, 2011 at 9:05 PM, Paul Davis<paul.joseph.davis@gmail.com>  wrote:
>> Do you monitor IO activity or system responsiveness when you're doing
>> this. I've seen some compactions wallop a system when it switches over
>> due to removing large old files and such. It doesn't sound like this
>> is big enough for that case but it might be something worth checking.
>>
>> On Fri, Oct 14, 2011 at 3:41 AM, Paolo Negri<paolo.negri@wooga.net>  wrote:
>>> Dear list,
>>>
>>> We have a script that does the following (strictly sequentially)
>>>
>>> 1) update 300K docs in a db
>>> 2) launch compaction of the db
>>> 3) poll at a 30 sec frequency http://127.0.0.1:5984/database to know
>>> when compaction completed
>>>
>>> Last night we got a timeout error during 3, we think that this might
>>> be because the first polling (GET  http://127.0.0.1:5984/database) is
>>> done right after triggering compaction
>>>
>>> I thought the dev team might be interested in knowing that this is happening
>>>
>>> There's no other activity on the couchdb instance other than what
>>> described in this email.
>>>
>>> ERROR unexpectd response checking compaction db: {ok,"500",
>>>                                                  [{"Server",
>>>
>>> "CouchDB/1.3.0a-74613f5-git (Erlang OTP/R14B04)"},
>>>                                                   {"Date",
>>>                                                    "Fri, 14 Oct 2011
>>> 01:46:37 GMT"},
>>>                                                   {"Content-Type",
>>>                                                    "text/plain; charset=utf-8"},
>>>                                                   {"Content-Length","350"},
>>>                                                   {"Cache-Control",
>>>                                                    "must-revalidate"}],
>>>
>>> <<"{\"error\":\"{timeout,{gen_server,call,[<0.21934.9>,{open_ref_count,<0.4090.13>}]}}\",\"reason\":\"{gen_server,call,\\n
>>>    [couch_server,\\n     {open,<<\\\"backup\\\">>,\\n
>>> [{user_ctx,\\n              {user_ctx,null,\\n
>>> [<<\\\"_admin\\\">>],\\n<<\\\"{couch_httpd_auth,
>>> default_authentication_handler}\\\">>}}]},\\n     infinity]}\"}\n">>}
>>>
>>>
>>> Thanks,
>>>
>>> Paolo
>>>
>
>


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