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:[email protected]]
Sent: 20 April 2012 08:35
To: [email protected]
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.
