Re: Synchronous Log Shipping Replication

On Tue, Sep 9, 2008 at 8:42 PM, Markus Wanner <markus(at)bluegap(dot)ch> wrote:
>> In the viewpoint of detection of a network failure, this feature is
>> necessary.
>> When the network goes down, WAL sender can be blocked until it detects
>> the network failure, i.e. WAL sender keeps waiting for the response which
>> never comes. A timeout notification is necessary in order to detect a
>> network failure soon.
>
> That's one of the areas I'm missing from the overall concept. I'm glad it
> comes up. You certainly realize, that such a timeout must be set high enough
> so as not to trigger "false negatives" every now and then?

Yes.
And, as you know, there is trade-off between the false detection of the network
failure and how long WAL sender is blocked.

I'll provide not only that timeout but also keepalive for the network between
the master and the slave. I expect that keepalive eases that trade-off.

regards

--
Fujii Masao
NIPPON TELEGRAPH AND TELEPHONE CORPORATION
NTT Open Source Software Center