[avahi] Automatically do something, when a service has been published?

[Trent Lloyd]

Hi Michael,

On 24/08/2008, at 2:14 AM, Michael Schmarck wrote:

> Hello.
>
> Using Avahi, can I setup the systems so, that they
> automatically do something, as soon as a service
> is available?
>
> More specific:
> I'd like to start a NFS client (ie. portmap and also
> autofs) on a notebook only, if there's one (or more)
> NFS server available.
>
> On the servers, I've added the following nfs.service
> file:
>
> <?xml version="1.0" standalone='no'?><!--*-nxml-*-->
> <!DOCTYPE service-group SYSTEM "avahi-service.dtd">
> <service-group>
>  <name replace-wildcards="yes">%h</name>
>  <service>    <type>_nfs._tcp</type>    <port>2049</port>  </service>
>  <service>    <type>_nfs._udp</type>    <port>2049</port>  </service>
> </service-group>
>
> When I now do a "avahi-browse -a", I see (amongst
> other things):
>
> --($ /etc/avahi)-- avahi-browse -a
> [...]
> + eth0 IPv4 HD                                            Network  
> File System  local
> + eth0 IPv4 HD                                             
> _nfs._udp            local
> [...]
>
> (The hostname is “HD”.)
>
> I could of course setup a cron job which runs every
> minute (or whatever period) and which calls “avahi-browse
> -t _nfs._tcp” and then does something. But I don't
> think that this is, uhm, “elegant” :)
>
> Can I somehow setup my systems (client and/or server)
> in such a way, that the client does “something” (eg.
> start NFS stuff, in my case) as soon as a service
> is available? I think the key here is “as soon as”.

Avahi doesn't support anything like this right now (some kind of  
'callout' based script for services appearing/disappearing)

You would need to write a new program making use of the Avahi API that  
did this.

Of course while mounting NFS mounts may seem useful.. actually  
stopping or starting portmap etc seems silly.. why not just leave it  
running?

Regards,
Trent