[mythtv-users] upgraded 0.28 on mythbuntu not finding proper backend

[Brian J. Murrell]

On Wed, 2016-07-20 at 05:16 +1200, Stephen Worthington wrote:
> 
> This could be the problem.  Using a DNS name instead of an IP address
> here can be dangerous.

It has never been a problem until upgrading to 0.28.

> From what you said, I am guessing that you
> have your own DNS server,

Yes.

>  and that name resolves to both an IPv4
> address

Yes.

>  and also to a link-local IPv6 address.

No.

$ host pvr.interlinx.bc.ca
pvr.interlinx.bc.ca has address 10.75.22.2
pvr.interlinx.bc.ca has IPv6 address 2002:...:214:d1ff:fe13:52fb
pvr.interlinx.bc.ca has IPv6 address 2001:...:214:d1ff:fe13:52fb
pvr.interlinx.bc.ca has IPv6 address fd31:aeb1:48df:0:214:d1ff:fe13:52fb

> But which one will any
> particular PC get?

Note that we are talking about the MasterServerIP database setting.
 Using "-v database --loglevel debug" I can see that this FE is not
even asking the database for that value, so this name vs. ip address
for the MasterServerIP is moot at this point.

In any case, I have tried an IPv4 address for MasterServerIP and it did
not resolve the problem.

> And at startup, is the DNS server available when the this address
> needs to be resolved so that the backend will listen on it?

Most certainly.

> If the
> networking is still coming up, the DNS server may not be accessible

It's on a completely different machine.

> Also, if the frontend PC is on a different subnet from the backend
> PC,
> using a link-local IPv6 address on the backend will not work.

Not relevant.  Same subnet, not using link-local addresses.

> It is
> quite unusual to have a global IPv4 address and a local IPv6 address
> on the same DNS name, as they have quite different uses.  It would be
> much better if the IPv6 address was a global unicast address, not a
> link-local one.

There is no link-local IPv6 happening here.  You are just assuming I am
using link-local addresses.  I'm not.  They don't appear in any
database field nor do they appear in any DNS records.

> I would try setting MasterServerIP to an IP address instead of a DNS
> name and see if that resolves the problem.

I did.  It does not.  But it's orthogonal because the FE doesn't even
ask the database for the MasterServerIP.  It does ask for
the BackendServerIP, but even when it gets a value for that, it still
ends up wanting to use localhost.

All very good thoughts and ideas but unfortunately none of them hit the
nail on the head.

As I write this, it does seem strange to me that the FE does not ask
for the MasterServerIP.  The FE that does work does ask for
the MasterServerIP.  I will go see in the source if I can see why an FE
would not ask for the MasterServerIP.

Cheers,
b.
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