On 19 Jul 2012, at 01:11, Aldo Zavala wrote:
> Hi, everybody.
>
> I was reading the "Deploying FreeRADIUS with the MySQL Cluster Database"
> whitepaper downloaded from MySQL website, it mentions in "3.1 Deployment
> Topologies" section that MySQL cluster can be integrated with FreeRADIUS but
> it always mention FreeRADIUS to be installed in a single node, would be a way
> to setup FreeRADIUS to be also failover the same way MySQL is, and not run
> just in a single node always?
Yes. You use multiple instances of the SQL module and point them at different
SQL nodes, the local node and then any other SQL node in the cluster.
You can then use the redundant construct to switch between them in case of
failure:
redundant {
sql
sql_remote0
sql_remote1
sql_remoteN
}
The problem is (with 2.1x and 3.0) is that if all the connections in the SQL
connection pool are down, the SQL module will only fail once its tried to
establish a new connection and failed.
Only one thread can be modifying the contents of the connection pool at a given
time because its protected by a mutex. Only one thread can try and open a new
connection, and until that connection succeeds or fails all the other threads
will block.
This causes a bottleneck where a bunch of threads block waiting for their turn
to try and re-establish the connection before failing over. Because the server
is largely stateless this happens on every request.
I believe a good fix would be to check the state of the pool and the mutex, and
if were at 0 connections and the pool is locked, to fail instantly. I'll talk
to Alan and see what he thinks, maybe it should be configurable.
If you're using SQL via a unix socket you should be fine, but as soon as you
hit a remote server where you have to wait for the TCP connection to time out,
I can almost guarantee that the server will just lock up completely.
So unlike the example above, i'd recommend you only specify one local node and
one remote node. Or wait and we'll try and fix something for 3.0.
-Arran
>
> Note: Before reply saying that this question should be posted in MySQL forums
> please consider that I am not asking about MySQL configurations, I am asking
> about FreeRADIUS product, many thanks to everybody!
>
>
> Aldo Zavala
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