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From Attila Nagy <...@fsn.hu>
Subject Re: CouchDB slow response times
Date Mon, 23 Apr 2012 07:06:37 GMT
Hi,

Yes, the cause is in the final setup, CouchDB will have a power of that, 
so I would like to benchmark what kind of performance it can deliver.
Am I right when I assume that HTTP pipelining won't give anything 
serious over multiple persistent connections (and no pipelining on them)?
(I've measured non persistent and persistent: 1700 QPS vs 2200, each of 
them gave 100% CPU usage from CouchDB)

On 04/20/12 17:55, Adam Kocoloski wrote:
> Hi Attila, I assume you have your reasons for limiting CouchDB to one core, but you should
be able to improve concurrent read performance by leveraging a few more of those cores on
your server.  This is Erlang, after all ;-)  I've seen BigCouch nodes pretty nearly saturate
Dual X5670s given enough concurrent readers.
>
> Also, HTTP pipelining allows you to submit multiple outstanding queries on the wire and
is fully supported in CouchDB.  Admittedly finding clients that do it well is not always an
easy task.  Regards,
>
> Adam
>
> On Apr 20, 2012, at 6:03 AM, Attila Nagy wrote:
>
>> Hi,
>>
>> What I need is a multi-site replicated document DB (well, most of the time a key-value
DB would also be fine, but CouchDB views are very handy for the rest, which spares me to build
my own indexes) where I can read and write all instances every time and the last modification
wins -whole document-.
>> Also, I don't like read repair, the DB should log the changes and replicate them
(having last update conflict resolution is fine as said) to the others when they can be reached.
>> For this specific application the read/write ratio is very high, like 5M:1 or higher.
>>
>> So CouchDB is a perfect fit, my only problem is it (for this particular case the
read performance) should be somewhat faster. Also, a different API would be good, with the
attributes of -say- LDAP:
>> - binary for quick processing
>> - multiple outstanding queries on the wire
>>
>> HTTP is easy to use, but I guess it adds somewhere 30-50% of the current processing
time (are there any exact measurements maybe?).
>>
>> I really think that april 1 post about switching to Java would bring more boost (at
least raw performance wise, from other perspectives, maybe Erlang is a good fit).
>> Waiting some hundred milliseconds for the GCs is fine with me if they don't happen
too often. ;)
>>
>> On 04/20/12 10:27, Mike Kimber wrote:
>>> Performance is relative and effective performance is very much determined by
the use case i.e. we do analytics with couchdb its faster than a traditional RDBMS in many
cases (especially if your views are queried regularly) on less hardware (disk space not included,
but that's a trade off and compression in 1.2 helps greatly here) and is easier to use for
document analysis. However it may not be a great fit for very high read use cases currently.
If that's your use case then there are other options i.e. Redis (possibly as a front end to
Couch) or dare I say it here Mongodb and Couchbase or numerous other commercial options from
in-memory databases to column orientated databases, but again it depends on the use case.
>>>
>>> You may want to describe your use case i.e. what you are trying to accomplish
to  allow the community to provide  informed comment on your observations.
>>>
>>> Thanks
>>>
>>> Mike
>>>
>>> -----Original Message-----
>>> From: Attila Nagy [mailto:bra@fsn.hu]
>>> Sent: 20 April 2012 08:35
>>> To: user@couchdb.apache.org
>>> Subject: Re: CouchDB slow response times
>>>
>>> On 04/19/12 08:28, Attila Nagy wrote:
>>>> So getting an exact document took .098921 seconds (nearly 98.9
>>>> milliseconds) on a completely idle machine.
>>>>
>>>> Any subsequent queries are in the order of the above response time,
>>>> which is just slow.
>>>>
>>>> Is this what CouchDB and Erlang capable of, or something is wrong in
>>>> my setup? I haven't turned compression off, BTW, but will measure its
>>>> effect.
>>> Without compression:
>>> 07:43:03.822390 HTTP GET /test/1
>>> 07:43:03.823475 HTTP/1.1 200 OK
>>> 07:43:03.919761 the JSON data
>>> so the response time is .097371 seconds (97.37 ms)
>>>
>>> In the mean time, I've found that somewhere in time CouchDB/HTTPd turned
>>> TCP NODELAY to off, so
>>> socket_options = [{nodelay, true}]
>>> gives: 2.47 ms response time, which is a major increase.
>>> I could lower that down to 2.1 ms by switching to
>>> null_authentication_handler, which is not good, but better.
>>>
>>> On query performance: when I fetch the same documents (one by one, ID
>>> number one to the last) from three different machines on four threads on
>>> each of them (so 12 concurrent HTTP GETs can be on the wire), I can
>>> saturate one CPU core (Xeon X5670 @ 2.93GHz, I've limited it to one
>>> core) to 100% CouchDB and can get about 1700 query/sec performance.
>>> These are just plain HTTP GETs, so no JSON parsing is involved.
>>> Switching to persistent connections gives 2200 query/sec (again, CouchDB
>>> maxes the CPU out).
>>>
>>> I hope some day CouchDB will be able to deliver performance too.


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