I'm dont know fully how the cache server works as i'm not really a
developer as such and i've never looked closely at the code, but I know
that its storing objects and not rows. and no we don't use hibernate.
Shahaf Abileah wrote:
Do you use hibernate or some other O-R mapping layer? Do you cache your data
as domain objects or are some Record representation?
--S
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Martin Eriksson
Sent: Friday, August 22, 2008 8:13 AM
Cc: [email protected]
Subject: Re: [Slony1-general] Slony over a WAN?
our cache server is all in-house written specifically for our
application/database, (as not all data is cached only things likely to
be access often etc)
but we do use java as language of choice, and the cache server is using
the sun java rmiregistry
cache server updated as soon as it picks up changes that come in from
the replication, its not perfect but it works pretty well. worst case
user will get an error message when trying to write to master db, but
then it will try to update the cache and by the time the cache is
updated the write will go through..
Shahaf Abileah wrote:
Thanks for the great info Martin.
If you don't mind me asking, what technology do you use for your cache? How do
you combine the data in a local site's cache with the (potentially different)
data in that local site's slave DB?
Thanks,
--S
-----Original Message-----
From: [EMAIL PROTECTED] [mailto:[EMAIL PROTECTED] On Behalf Of Martin Eriksson
Sent: Friday, August 22, 2008 12:54 AM
Cc: [email protected]
Subject: Re: [Slony1-general] Slony over a WAN?
Hi, we do slony over WAN where W = World hehe
Our master Database is in London, then we got one node in Cyprus, one
node in San Fransisco, and then one node in Frankfurt and about to add
another node in Hong Kong. Our database is only around 8 gigs though.
we got a bit of a special setup in terms of the applications using the
dbs as we want our application to read locally but write to the master
so we a pretty advanced cache system for handling if Bill is sitting In
San Fransisco writes to the db and then look at the data he sees the
data he just wrote so does everyone else in that office even though it
might not have been replicated to his local db yet. this work pretty
good, we never have more then 5-15 seconds delay on slony event across
the globe so in worst case if someone tries to change something that
already been changed it wont work and they just reset their cache (which
takes 2 minutes) and then they continue working.
and we do have an AWFUL line london <-> Cyprus that on average does
40kbytes/s which is horribly low. But it still works 100 times better
then having both read and write going to London all the time from across
the world..
Of course if the shit hits the fan so to say when we do DLL changes
which happens every 3 months for release and we cant recover it will
take up to 72 hours to replicate to all nodes (which is not really an
option)
but if you got good bandwidth between your nodes its not a problem.
Though if you got a 80 gig db you might want to consider not replicating
it across the WAN as it will take quite a long time and might cost your
a lot depending on your ISP i guess.. well if you got a gigabit line and
dont mind using it then I guess you are fine :) but if you bandwidth is
limited you could do as we do sometime,
setup a second db instance on your masternode (assuming node and master
will be in the same hardware architecture) do a replication to the local
instance once done shut down that instance move the whole /data
directory of that instance onto so movable disk, and drive down to the
other node load it up, modify path to the node using slony store path
and fire it up and let it catch up on the last hour or so of the new data.
slon processes should run in the same "network context" as the node that
each is responsible for managing so that the connection to that node is a
"local" one.
Do not run such links across a WAN.
Its already been covered but I'll add to it. Yes you should run the slon
process on the node in question do not run them all on the master node,
not only because it will work better also because when you do have
multiple slon process running on one machine it can get VERY confusing
figure out which one goes where and which one is having connections
open. Life is much easier if one slon process run on each node machine.
good luck!
Martin
Mark Steben wrote:
Looking for advice on how to proceed. We are running Postgres 8.2.5 in Lee,
Massachusetts. We will be installing same in Norfolk Virginia in the not
too distant future. Our need is to replicate roughly 60 - 70 percent
Of our 80 GB database in Lee over a WAN to Norfolk for reporting purposes.
In reading 'Slony-1 Best Practices' on the Website I came across the
following statement:
slon processes should run in the same "network context" as the node that
each is responsible for managing so that the connection to that node is a
"local" one.
Do not run such links across a WAN.
Does this still hold true? If not I would like to hear experiences of
anyone engaging in a 'Slony-1 long distance relationship'
Any other alternatives to consider? I do run Slony-1.2.14 in development
with everything encompassed in Lee. However
we will be opening another office 35 miles west in West Springfield that I
will be operating out of. I plan on employing Slony-1
To provide replication between these 2 'not so long distance' locations.
Any comments welcome. Thanks
Mark Steben│Database Administrator│ @utoRevenueT
480 Pleasant Street, Suite B200, Lee, MA 01238
413-243-4800 x1512 (Phone) │ 413-243-4809 (Fax)
A Division of Dominion Enterprises
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