Re: Design Questions about static factory classes

Tom Anderson <>
Mon, 24 May 2010 13:15:58 +0100
On Sun, 23 May 2010, Arne Vajh?j wrote:

On 23-05-2010 20:18, Rhino wrote:

On May 23, 6:35 pm, Arne Vajh?j<> wrote:

On 23-05-2010 17:33, Rhino wrote:

Tom Anderson<> wrote in

And then deploy the JAR and reboot. Not so hot if you're hoping to run
a global ecommerce site.

I didn't realize you needed to reboot to get the new Jar to take effect.
That's lousy. Isn't it possible to simply refresh the new Jar in place
without rebooting? I'm pretty sure Tomcat lets you redeploy a Jar without
stopping Tomcat first but my Tomcat skills are rusty so I may be

If you can discard the classloader, then you can do that instead
of restarting the JVM.

But it is still an interruption of production.

In tomcat that is what happens when you restart just the app
and not the entire server.

Whatever happened to the time-honoured tradition of maintenance
windows? I don't think I've ever heard of a system that was truly 24 x
7. All of them used to have scheduled downtimes (or at least the
option of having downtimes as needed) for things like taking backups
and so forth. Do real-life Internet online systems _really_ promise 24
x 7? Don't the executives and/or lawyers build in at least some
provisions for downtime into their contracts?

I'm sure that people buying systems push for those downtimes to be as
brief and infrequent as possible but surely their must be _some_
provision for it in web-based systems? Or am I behind the times?

It depends on the context.

For many internal systems then nightly downtime is still

But the world has become global. It is always work hours
somewhere on the planet.

Public internet systems like Google and FaceBook does
not close a couple of hours every day.

Huge multinational corporations with offices in almost
all timezones can not shutdown business critical system
a couple of hours every day.

Nightly downtime still exists but it is definitely
out of fashion today.

Many business system still have weekly/monthly
scheduled downtime though.

But Google/FaceBook types does not even have that.

We're no Google, and we will have downtime when we do need to update the
code. But pushing new content may well be happening on a daily basis, and
we don't want daily maintenance outages.

Mind you, if you have a cluster of app servers, you can update the code on
a machine-by-machine basis without ever taking the whole cluster down.
Provided you don't change the interface between machines, that is. I
anticipate that we'd be able to do this, althoug whether it'll be
considered worth setting up to avoid a few minutes of downtime, i don't


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