Re: [Qemu-devel] [PATCH v13 3/3] block/gluster: add support for multiple gluster servers

[Prasanna Kumar Kalever]

On Tuesday, November 10, 2015 10:54:25 PM, Jeff Cody wrote:
> 
> On Tue, Nov 10, 2015 at 02:39:16PM +0530, Prasanna Kumar Kalever wrote:
> > This patch adds a way to specify multiple volfile servers to the gluster
> > block backend of QEMU with tcp|rdma transport types and their port numbers.
> > 
> > Problem:
> > 
> > Currently VM Image on gluster volume is specified like this:
> > 
> > file=gluster[+tcp]://host[:port]/testvol/a.img
> > 
> > Assuming we have three hosts in trusted pool with replica 3 volume
> > in action and unfortunately host (mentioned in the command above) went down
> > for some reason, since the volume is replica 3 we now have other 2 hosts
> > active from which we can boot the VM.
> > 
> > But currently there is no mechanism to pass the other 2 gluster host
> > addresses to qemu.
> > 
> > Solution:
> > 
> > New way of specifying VM Image on gluster volume with volfile servers:
> > (We still support old syntax to maintain backward compatibility)
> > 
> > Basic command line syntax looks like:
> > 
> > Pattern I:
> >  -drive driver=gluster,
> >         volume=testvol,path=/path/a.raw,
> >         servers.0.host=1.2.3.4,
> >        [servers.0.port=24007,]
> >        [servers.0.transport=tcp,]
> >         servers.1.host=5.6.7.8,
> >        [servers.1.port=24008,]
> >        [servers.1.transport=rdma,] ...
> > 
> > Pattern II:
> >  'json:{"driver":"qcow2","file":{"driver":"gluster",
> >        "volume":"testvol","path":"/path/a.qcow2",
> >        "servers":[{tuple0},{tuple1}, ...{tupleN}]}}'
> > 
> >    driver      => 'gluster' (protocol name)
> >    volume      => name of gluster volume where our VM image resides
> >    path        => absolute path of image in gluster volume
> > 
> >   {tuple}      => {"host":"1.2.3.4"[,"port":"24007","transport":"tcp"]}
> > 
> >    host        => host address (hostname/ipv4/ipv6 addresses)
> >    port        => port number on which glusterd is listening. (default
> >    24007)
> >    transport   => transport type used to connect to gluster management
> >    daemon,
> >                    it can be tcp|rdma (default 'tcp')
> > 
> > Examples:
> > 1.
> >  -drive driver=qcow2,file.driver=gluster,
> >         file.volume=testvol,file.path=/path/a.qcow2,
> >         file.servers.0.host=1.2.3.4,
> >         file.servers.0.port=24007,
> >         file.servers.0.transport=tcp,
> >         file.servers.1.host=5.6.7.8,
> >         file.servers.1.port=24008,
> >         file.servers.1.transport=rdma
> > 2.
> >  'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol",
> >          "path":"/path/a.qcow2","servers":
> >          [{"host":"1.2.3.4","port":"24007","transport":"tcp"},
> >           {"host":"4.5.6.7","port":"24008","transport":"rdma"}] } }'
> > 
> > This patch gives a mechanism to provide all the server addresses, which are
> > in
> > replica set, so in case host1 is down VM can still boot from any of the
> > active hosts.
> > 
> > This is equivalent to the backup-volfile-servers option supported by
> > mount.glusterfs (FUSE way of mounting gluster volume)
> > 
> > Credits: Sincere thanks to Kevin Wolf <address@hidden> and
> > "Deepak C Shetty" <address@hidden> for inputs and all their support
> > 
> > Signed-off-by: Prasanna Kumar Kalever <address@hidden>
> 
> 
> Previous versions of this commit mentioned that the new functionality
> is dependent on a recent fix in libgfapi.  This commit message is
> missing that line; does its absence mean that the new functionality is
> not dependent on any particular libgfapi version?
> 
> What happens if the new functionality is tried on the last stable
> libgfapi release?

Sorry for not removing this since long, actually the libgfapi fix is for 
defaults values
i.e. When glfs_set_volfile_server is invocated multiple times, only on the first
invocation gfapi code replace port 0 with 24007 and transport NULL with "tcp".

Any have to remove this dependency, I have put up code that will take care of 
defaults.

Thanks,
-prasanna 

Hence, replacing the parameters at the entry function is the right way.
> 
> Thanks!
> Jeff
> 
>