Thanks for the very interesting discussion!
Benjamin's proposal to distinguish between the replication of "app dbs"
on different hosts and replicating the design documents between
"customer dbs" on the same machine and CouchDB instance reduces the
http-traffic and supports scaling over many machines.
Nevertheless I wonder why, if I really want the design documents to be
identical for all customers - and this is what multi-tenancy demands - I
must replicate the app documents to every db on the same instance. The
ability to replicate to different instances greatly provides for
scalability. But wouldn't it be much simpler to operate and would
consume less resources (don't forget the file-I/O!) if all the dbs on
one instance could share the same application documents?
Ciao
Gregor
On 01.11.2010 18:46, Benjamin Young wrote:
Martin,
I'm not sure what your setup is, but if you had an "app" database (the
authoritative db for the _design doc you want to share with customers) on
the same instance of CouchDB with the customer's db's, then your replication
requests would all be local--no IP connections what so ever.
To do that in a multi-instance scenario, you could simply have the app db's
continuously replicate between the instances, and locally replication to the
customer db's on each particular instance. Or, if you don't want to use
replication between your instances, you could push your changes into the
"app" db's on each of the instances. In either case, you'd only be
generating HTTP traffic on the pushing of the app and/or replication of the
"app" db's between the machines--so, very low network overhead in either
case.
Later,
Benjamin
On Mon, Nov 1, 2010 at 11:10 AM, Martin Higham<[email protected]>wrote:
'Continuous' replication to thousands of databases means thousands of
permanent IP connections. The alternative is that you write a script that
fires off replication requests in sequence for all your databases to
perform
the update. As you say, this shouldn't occur often.
Martin
On 1 November 2010 14:48, Benjamin Young<[email protected]> wrote:
Martin,
Why not? It's only going to be sending changes. Unless you're constantly
updating your app installation or those changes are massive, you
shouldn't
run into any trouble.
Your other option is the "middle-ware" setup, but then you'd loose the
power
of application replication.
Thoughts?
Later,
Benjamin
On Mon, Nov 1, 2010 at 10:30 AM, Martin Higham<[email protected]
wrote:
Until you have one DB per user and then you're looking at replicating
the
design doc to many thousands of databases and continuous replication
doesn't
make sense
Martin
On 1 November 2010 14:11, Benjamin Young<[email protected]>
wrote:
Hey Gregor,
If you setup continuous replication between your various customer
db's
and
your primary application database (which would likely only contain
the
main
app's design doc), then publication of the app would automatically be
"rolled out" to the various customer db's. Because these DB's would
be
"standalone" versions of the app, they could even be on multiple
hosts
running CouchDB, so you'd remove the single point of failure problem
that
most web-apps have--as they run (often) through a single server for
all
customers.
Personally, that mode of "multi-tenant" app (via replication) is
pretty
exciting, and opens up new ways of dealing with load and application
distribution. Get's the mind reeling, or maybe that's the coffee I
just
finished... :)
Later, Gregor,
Benjamin
On Mon, Nov 1, 2010 at 6:49 AM, Jan Lehnardt<[email protected]> wrote:
Hi Gregor,
On 1 Nov 2010, at 08:12, Gregor Frey wrote:
Hi,
when I followed the discussion about the setup of CouchDB in a
hosted
environment, I wondered whether it would be possible to share the
application level software between multiple databases. This would
enable
a
real multi-tenant set-up. Otherwise you must duplicate the
application
with
each new tenant.
Does anybody know whether and how CouchDB supports application
sharing?
CouchDB does not support application or document sharing over
databases.
But nothing stops you from gradually replicating a new design doc
(the
application) to every database.
Cheers
Jan
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