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From Michi Mutsuzaki <mi...@cs.stanford.edu>
Subject Re: adding a separate thread to detect network timeouts faster
Date Thu, 12 Sep 2013 18:05:18 GMT
On Thu, Sep 12, 2013 at 12:05 AM, Rakesh R <rakeshr@huawei.com> wrote:
> AFAIK, ping requests would not involve any disk I/O, but it would go through the RequestProcessor
chain and executes sequentially.

Yes, that's what I meant. Ping requests don't touch disk, but they do
go through the commit processor. So if a ping request is behind a
write operation that takes a long time, the ping request will be
affected. This is done intentionally to take the disk into account for
the heartbeat mechanism.

Anyways, I misunderstood what Jeremy was proposing. He wants to keep
the session timeout relatively high to tolerate slow disk, but at the
same time detect non-disk failure (node down, network partition) more
quickly.

I think this can be done purely on the client side. Create a separate
thread that sends a 4 letter word command like ruok periodically, and
close the socket if the client doesn't get the response within certain
amount of time.

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