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From Jason Smith <...@iriscouch.com>
Subject Re: Building substantial "pure" 2 tier CouchApps - feasible?
Date Tue, 12 Jul 2011 02:06:49 GMT
tl;dr summary: It is practical using external processes to check in
and keep things sane. This is very future-proof, but with a slightly
longer time-to-market.

On Tue, Jul 12, 2011 at 6:18 AM, Andrew Stuart (SuperCoders)
<andrew.stuart@supercoders.com.au> wrote:
> I'd like to build a rather substantial application, it would be nice to
> build it as a pure 2 tier CouchApp.

Many have tried.

It is completely impractical to build a pure 2-tier Couch app.
However, two tiers, plus external helpers ("2.1 tier") is very
practical.

We've got some difficult days ahead. But it doesn't really matter with
me now. Because I've been to the mountaintop. I don't mind. Like
anybody, I would like to build a full-featured Couch app; scalability
has its place. But I'm not concerned about that now. I just want to do
God's will. And He's allowed me to go up to the mountain. And I've
looked over. And I've seen the Promised Land. I may not get there with
you. But I want you to know tonight, that we, as a people, will get to
the Promised Land. So I'm happy, tonight. I'm not worried about
anything. I'm not fearing any <span>.

What I prefer is this: Your programmers develop on and deploy to the
Couch. Your users also interact directly with the Couch. However,
*external agents* also access the couch and perform administrative
tasks as needed.

The benefits of two-tier apps are obvious; I will list a few:

* Simpler
* Reduced sysadmin workload
* Excellent future-proofing: multi-datacenter, offline operation, run
from an iPhone, etc.

Unfortunately, real-world apps are more than a pretty web page. To name a few:

* Send emails or other messages (e.g. push notifications)
* Help users recover their password
* Interface with related services: boot EC2 instances, update a DNS
entry, generate an certificate
* Notice that somebody is spamming and do the needful
* Ops stuff: run backups, rotate logs, monitor services. Maybe that's
an external responsibility; but IMO nowadays that is an application's
self-hygeine
* Catch unexpected errors, reassure the user, alert the staff

There is no alternative. You need a third component--admin stuff--to
build a comprehensive service. But should that component be a blockade
between your users and their data? Or should it work behind the
scenes? Finally, note that external agents needn't have the same
quality as middleware. An exception here or crash there is not
devastating to the user experience. (Perhaps emails are delayed, or a
backup is missed. That is better than 500 INTERNAL SERVER ERROR.)

I use NodeJS scripts to this end. For a few weeks, one such agent ran
from my laptop, over DSL! Hey, it's HTTPS to a Couch in EC2. What does
it matter? Similarly, our web site is compiled to static HTML by a
couchapp. That app only runs on Chrome/OSX. I've no idea why, nor do I
care. The "compiled" site supports all browsers and loads rather
quickly (for EC2).

-- 
Iris Couch

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