On 11-06-26 10:48 PM, rodney wrote:
> Hi
>
> I'm trying to setup slony to replicate table from one master to around
> 200 slaves. Can slony support slave number at this scale? It is observed
> in pgadmin that when I have 1 slave, the num of listener is 1. However,
> when I have 2 slaves, the num of listener increase from 1 to 4 (not 2).
> Will this be a problem if the slave go to a large number, like 100?
>
>
> Best regards

Running 200 slaves isn't a common use case for slony.
That doesn't mean it won't work.  I know of at least one person who is 
doing about 50 slaves, but I don't have details on the setup.

If your going to try Slony with 200 slaves this would be my advice

* Expect to encounter issues along the way, you will need to figure out 
the best way to deploy and tune things

* Slony supports the idea of cascaded subscribers.   You can have node 
something like

     1
     |
     V
     2
    / \
   3   4

so you can have a number of direct subscribers then feeding a number of 
slaves.   Creating a layered network would probably work better than 
having 50 or 100 subscribers off a single node.

* Slony also supports something called 'log shipping' where the slon on 
a slave generates .sql files that can then be applied to other nodes 
downstream.  Since these other nodes are not technically part of the 
slony cluster (they don't have paths, or slon daemons) you can 
distribute the .sql files to as many machines as you want.  This might 
work for you

* In a slony cluster each node must confirm SYNC messages from EVERY 
other node even when a direct path between them doesn't exist (this 
explains  for the number of listeners you see in pgadmin).  At a 100 
nodes there will be a lot of SYNC/confirm messages.  You will probably 
have to increase the SYNC interval so you have fewer syncs going on.


* If you try any of this let us know what works or doesn't

Steve