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From J Chris Anderson <>
Subject Re: Scalability of _changes api?
Date Fri, 06 Aug 2010 20:55:14 GMT

On Aug 6, 2010, at 1:38 PM, Talib Sharif wrote:

> Hey All,
> Do people have experience with the scalability and performance of the _changes api in
general, and especially when using with filters?
> How many connections can be kept open?

If you use a JavaScript filter, you will have more limited concurrency that with an Erlang
filter, as the JS filters run in their own OS process. CouchDB tries to be reasonably efficient
with these, but they are still much more heavyweight than the Erlang ones.

> And is the changes api function of size/updates/total_no_documents?

I think the _changes API should have no scalability issues, as the wall you will hit long
before running an (Erlang) changes filter will be the insert / update rate of the database

If you were to say, make thousands of concurrent changes requests, with varying since=Seq
params, that would be the worst case, so you can test that work load if you want to find boundaries
conditions. (Bottleneck here would be for disk IO reads I think).


> Thanks,
> Talib

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