Riak-CS issues when Riak endpoint fails-over to new server

Toby Corkindale toby at dryft.net
Tue Jan 3 20:04:09 EST 2017


Hello all,
Now that we're all back from the end-of-year holidays, I'd like to bump
this question up.
I feel like this has been a long-standing problem with Riak CS not handling
dropped TCP connections.
Last time the cause was haproxy dropping idle TCP connections after too
long, but we solved that at the haproxy end.

This time, it's harder -- we're failing over to a different Riak backend,
so the TCP connections between Riak CS and Riak PBC *have* to go down, but
Riak CS just doesn't handle it well at all.

Is there a trick to configuring it better?

Thanks
Toby


On Thu, 22 Dec 2016 at 16:48 Toby Corkindale <toby at dryft.net> wrote:

> Hi,
> We've been seeing some issues with Riak CS for a while in a specific
> situation. Maybe you can advise if we're doing something wrong?
>
> Our setup has redundant haproxy instances in front of a cluster of riak
> nodes, for both HTTP and PBC. The haproxy instances share a floating IP
> address.
> Only one node holds the IP, but if it goes down, another takes it up.
>
> Our Riak CS nodes are configured to talk to the haproxy on that floating
> IP.
>
> The problem occurs if the floating IP moves from one haproxy to another.
>
> Suddenly we see a flurry of errors in riak-cs log files.
>
> This is presumably because it was holding open TCP connections, and the
> new haproxy instance doesn't know anything about them, so they get TCP
> RESET and shutdown.
>
> The problem is that riak-cs doesn't try to reconnect and retry
> immediately, instead it just throws a 503 error back to the client. Who
> then retries, but Riak-CS has a pool of a couple of hundred connections to
> cycle through, all of which throw the error!
>
> Does this sound like it is a likely description of the fault?
> Do you have any ways to mitigate this issue in Riak CS when using TCP load
> balancing above Riak PBC?
>
> Toby
>
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