Hi Neil,
I understand that split brain is not supported
but I do not believe what I am asking is unreasonable.
Is it ? ;-)
When a controller received a transaction, it knows
if it is able to send it to the other controller.
I want to detect (And probably log) when it is unable
to send the transaction to the other controller.
The fact is that Sequoia is designed to work with any number of
controllers. A one controller configuration can be perfectly ok (other
controllers can not be already started or under maintenance). So Sequoia
just handles the case where a controller that has been sent a query
fails but if there is only one controller available, this is not
considered has an issue since there is nothing to tell how many
controllers are 'supposed' to be in the cluster.
So to answer your question, a controller only knows if it was not able
to send a query to another controller if that other controller fails
exactly when the message is being sent.
Also, if a controller attempts to commit a transaction,
I would like to detect if that commit failed.
If a commit fail on all controllers, you will get an exception back. If
it fails only on one controller but succeeds on the other, you will not
see the error (you can change that behavior in the
DistributedRequestManager implementation).
There have to be point in the code where these situations
are detectable. I am asking for some guidance in helping
to find them.
I am willing to contribute patches to Sequoia since other
users may find these functions useful as well.
I am not really sure to understand what problem you are trying to solve
here. As you cannot distinguish a split brain from a real failure or a
simple maintenance procedure, I don't see how you are going to handle
all these cases in a generic way.
Please don't hesitate to elaborate on your ideas.
Thanks,
Emmanuel
--
Emmanuel Cecchet
Chief Scientific Officer, Continuent
Blog: http://emanux.blogspot.com/
Open source: http://www.continuent.org
Corporate: http://www.continuent.com
Skype: emmanuel_cecchet
Cell: +33 687 342 685
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