incubator-cassandra-user mailing list archives

Site index · List index
Message view « Date » · « Thread »
Top « Date » · « Thread »
From Robert Coli <>
Subject Re: CQL flow control
Date Wed, 05 Feb 2014 18:55:48 GMT
On Wed, Feb 5, 2014 at 6:14 AM, Ben Hood <> wrote:

> What is the general approach to this from a server perspective? Is
> there any flow control that the server can apply to back pressure onto
> the sending driver?

No. In theory the client could look at dynamic snitch scores, I suppose, if
the dynamic snitch worked right...

For most clients, my belief is the only backpressure is that, once a node
is severely overloaded, it will stop attempting to write hints and return
an OverloadedException. But this is only on the hint write path, not the
normal write path.

> If not, how do other driver implementors view this situation? Do you
> try to maintain some kind of flow control at the driver level so that
> you can push back onto the app, or you just let the effects of IO
> saturation just bubble up to the app?

I think most deploys of Cassandra deal with this reality by carefully
managing available capacity so that they don't risk getting in this

I understand that is not a technical solution appropriate to your
question's scope, but I do believe it describes the status quo.


View raw message