On Mon, Jun 11, 2012 at 11:09 PM, Patrick Hunt <[email protected]> wrote:
> On Sun, Jun 10, 2012 at 2:42 PM, Adam Rosien <[email protected]> wrote: > > Various people in my company are using zk as a pure high-throughput > > read-only cache (only get() operations) and I am trying to convince them > > this is a bad idea. Specifically: > > > > * I believe their clients do not manage (or do not manage well) > persistent > > connections, so there is a high amount of connection/session churn. > > * This churn results in increased quorum writes, because creating a > session > > is a quorum operation. (Is this correct? Looking at snapshot log dumps, > it > > seems so.) > > That's correct. > > > * Increased quorum writes from read-only operations is bad. > > Why? Not sure I follow the thinking here. (esp if you fix session > handling to be longer lived) > Only because the workload is read-only and short-lived, and I can't make the sessions long-lived, they are from a web server. :/ > > > > > To avoid this situation, one could: > > > > 1. Not do this. > > 2. Create a read-only connection/session that doesn't involve the quorum > or > > writing, somehow. > > I believe Facebook has been working on something like this - a "server > local session" for things like r/o clients. > > > 3. Something else. > > > > How could one do #2? Do observers allow #2? Any other suggestions? > > > > Perhaps someone from FB might be able to comment on their progress... > > Patrick >
