Hi Gérard,
On 1/24/07, Gérard BUNEL <[EMAIL PROTECTED]> wrote:
With the following configuration: 2 controllers having each 1 Virtualdatabase
supported by 2 backend (RAIDB1).
- When All backend of a controller are failed: My understanding is that
Failover mechanism is used and requests should be redirected to the second
controller.
Is my understanding correct ? And if yes is the driver responsible of this
redirection ?
Yes, it's correct but the JDBC driver is only responsible for the load
balancing/failover between the two controllers so it's used for
controller failures not backend failures. Backend failures are
directly managed by the controllers.
I made a test a few weeks ago with only the controller with no backend
in the JDBC URL used by the driver and the queries were directly
rerouted to the controller with active backends from the controller
with only failed backends.
- Let's imagine that we stop the controller holding failed backends. What
happens if we restart this controller and if its configuration automatically
loads the virtualdatabase configuration. Are the backends considered as
disabled ?
Yes, they should be considered disabled as they are not in a consistent state.
Sequoia tries to enable them if you set autoEnableBackends to true but
won't do it if the backends are not consistent. Sequoia needs to have
a checkpoint for the backend to know which queries of the recovery log
it needs to replay. It won't have one if the backend failed.
For example, if you disable a backend manually, Sequoia will register
a checkpoint in the recovery log so when you reenable it, it will be
able to replay the recovery log from the checkpoint.
- If None of the backend were failed, but instead we have a controller
failure. What happens when restarting the controller having its configuration
automatically loading the virtualdatabase configuration ?
Controller failed -> backends are not safe anymore so you should have
the same behaviour than above.
--
Guillaume
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