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From: Paul Davis <paul.joseph.davis@gmail.com>
Date: Mon, 23 Nov 2009 17:41:44 -0500
Message-ID: <e2111bbb0911231441n676664bdm230677e6b0fe1f51@mail.gmail.com>
Subject: Re: all_dbs_active - what should an app do when it gets this?
To: user@couchdb.apache.org
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On Mon, Nov 23, 2009 at 5:35 PM, Jeff Macdonald <macfisherman@gmail.com> wrote:
> Hi all,
>
> I have a simple app that is creating a lot of databases. Eventually
> when I get to some number of databases, I get this error
> all_dbs_active on insert. I thought I just sleep (ick) and try again,
> but when I went to Futon after the program was done for many minutes,
> I get that error in the web interface too. So I'm rather puzzled at
> what to do. I'm sure there is some config var somewhere where I can up
> that limit, but I'm more interested in what the proper thing to do
> when such a limit is met.
>
> TIA
>
> --
> Jeff Macdonald
> Ayer, MA
>

Other than increase the max_open_dbs configuration option, I can't
think of anything 'elegant' that you could do client side other than
backoff in your script for the db creation/access rate.

The limit comes from trying to avoid throwing random file descriptor
limit errors, so I'm not sure what the best solution would be. It'd
theoretically be possible to create a queue that would just block
client access to a db until there was an active slot available, but
that could be easily pushed into starvation if the open db's remain
active long enough which could be indefinite with things like
continuous replication IIUC.

HTH,
Paul Davis