FreeTDS Development Group

[Frediano Ziglio <freddy77 AT gmail.com>]

Il giorno gio 22 dic 2022 alle ore 17:10 Christopher Stevenson
<christopherd1682 AT gmail.com> ha scritto:
>
> Hello FreeTDS Support and Contributors,
>
> I am using FreeTDS to connect to always on availability groups running
> Microsoft SQL Server. I have not found much documentation regarding
> MultiSubnetFailover (
> https://learn.microsoft.com/en-us/dotnet/framework/data/adonet/sql/sqlclient-support-for-high-availability-disaster-recovery)
> support in FreeTDS. Therefore, I am confused about whether FreeTDS supports
> it or could potentially support Multi Subnet Failovers.
>

Hi Christopher,
   this feature is not currently implemented.

Reading the documentation is not clear to me what it's exactly
supposed to do. The page refers to some connection repetition. However
it is not clear the reference to the "multi subnet".
The code (see tds_open_socket in src/tds/net.c) tries to connect to
all DNS addresses so it seems it's doing the right thing in any case.

> When reviewing this mailing list, I found this thread:
> https://lists.ibiblio.org/sympa/arc/freetds/2016q2/029901.html but this
> does not go into detail about whether FreeTDS supports Multi Subnet
> Failover functionality or could support it.
>
> I would greatly appreciate any assistance or context that anyone could
> provide about using this MS SQL feature in a FreeTDS configuration. If this
> is not supported yet, I would like to know if this is something possible to
> add into the library.
>

These configurations are a bit hard to do on CI requiring uncommon
setups and potentially specific licensing.
Can you do some tests with the cluster (shutting down nodes and trying
to MS drivers) to see what that parameter change is exactly causing?

> Thank you so much,
> Christopher

Frediano