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On Wednesday 30 October 2002 09:58, Peter Mueller wrote:
> > I think my statement misled you to the problem of healthcheck. My problem
> > is, since the VIP is doing forwarding, then if the realserver is down but
> > the healthcheck think it hasn't go down (because the healthcheck checks,
> > let's say every 500ms), will the connection be lost (i.e. the client need
> > to refresh the browser)? I'm not an expert in this, so the answer might
> > be so obvious. Is there anyway (other than changing the healthcheck to
> > 10ms or less, or having the client to refresh the browser) to make the
> > director forward it to another realserver?
>
> 10ms = 0.001s!
>
> You can change the healthchecks to almost any time you want, but 10ms seems
> an awfully small number to me. I foresee big problems if you use 10ms; for
> example no real services in service...
>
> What application in the world needs health checks of 10ms? Can you
> describe your topology for us in detail so we can be helpful? For example,
> maybe you use apache + tomcat with mysql backend and all your clients are
> java applications over http.
>
Well, I'm really a beginner in LVS, so 10ms is probably blatantly wrong :)
I'm still evaluating LVS, and have no final topology yet. My current plan is
to have LVS-DR, with the realserver serving Apache with PHP, connected to
mysql backend. All PHP applications reside in a distributed filesystem,
probably coda or intermezzo.
My objective for a realserver outage is:
1) client not having to refresh their browser
2) client need not reauthenticate (for https connection)
What I mean by a realserver outage is (in steps):
1) healthcheck polls that realserver1 is up
2) then immediately after that realserver1 is down
3) director is forwarding new connection to realserver1
What will happen to that connection? Will it be lost (in which case my
objective 1 is not met)? Will it be forwarded to another realserver?
For objective (1), I can't find any other way but to decrease the healthcheck
polling time.
For objective (2), would putting PHP applications in a distributed filesystem
help?
Thank you.
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