[f-nsp] multiple service failover

[Manu Chao]

i am sure a vendor like f5 will help you to overcome your applications
limitations
On Tue, Jul 14, 2009 at 4:26 PM, David Miller <syslog at d.sparks.net> wrote:

> Hi All;
>
> I've got a situation that I'm not sure of the best way to handle.
>
> I have a pair of servers that are able to run the same application.
>  Caching issues make it weird though.  The application writes to the
> database when updates come in, and (of course) updates its own internal
> cache.  The servers don't update each other, however, nor do they get
> updates from the database any time other than at startup.  "startup" in this
> case is defined as the first query that hits tomcat.
>
> What this means is that I want to run off S1 as long as its running.  And
> if S1 becomes unavailable I want to run off S2 until I come back and fix
> things. lb-pri-servers takes care of that part.
>
> Here's the complicated part.  The servers accept SSL as well for user
> authentication.  I need http and ssl to fail to S2 as a pair - both or
> neither.  We recently had application response issues where S1 was very slow
> to respond, and http failed over but ssl did not.  This broke the customers
> ability to authenticate.  We're terminating ssl on the ServerIron 4G's and
> talking plaintext on port 443 to the server.  Apache is listening on 80 and
> 443 expecting plaintext.
>
> We've played with boolean health checks, but I haven't implemented them.
>  I'm concerned about separate health checks because nothing different is
> being tested.  It seems like a race condition would still exist where http
> would fail over, but a second later the ssl check would pass.  What we need
> is for a single failed health check to down the server and fail all services
> over to the backup.
>
> If it makes things easier, we can just skip the ssl test.  A single test
> for http is adequate for making sure apache is responding on the server.
>
>
> Suggestions very welcome.
>
> --- David
>
>
>
>
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