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

[Jeff Cody]

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?

Thanks!
Jeff