Re: [Qemu-devel] [PATCH v20 5/5] block/gluster: add support for multiple gluster servers

[Markus Armbruster]

One more...

Prasanna Kumar Kalever <address@hidden> writes:

> 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
>
> Say we have three hosts in a trusted pool with replica 3 volume in action.
> When the host mentioned in the command above goes down for some reason,
> the other two hosts are still available. But there's currently no way
> to tell QEMU about them.
>
> 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,[debug=N,]
>         server.0.type=tcp,
>         server.0.host=1.2.3.4,
>         server.0.port=24007,
>         server.1.type=unix,
>         server.1.socket=/path/socketfile
>
> Pattern II:
>  'json:{"driver":"qcow2","file":{"driver":"gluster",
>        "volume":"testvol","path":"/path/a.qcow2",["debug":N,]
>        "server":[{hostinfo_1}, ...{hostinfo_N}]}}'
>
>    driver      => 'gluster' (protocol name)
>    volume      => name of gluster volume where our VM image resides
>    path        => absolute path of image in gluster volume
>   [debug]      => libgfapi loglevel [(0 - 9) default 4 -> Error]
>
>   {hostinfo}   => {{type:"tcp",host:"1.2.3.4"[,port=24007]},
>                    {type:"unix",socket:"/path/sockfile"}}
>
>    type        => transport type used to connect to gluster management daemon,
>                   it can be tcp|unix
>    host        => host address (hostname/ipv4/ipv6 addresses/socket path)
>    port        => port number on which glusterd is listening.
>    socket      => path to socket file
>
> Examples:
> 1.
>  -drive driver=qcow2,file.driver=gluster,
>         file.volume=testvol,file.path=/path/a.qcow2,file.debug=9,
>         file.server.0.type=tcp,
>         file.server.0.host=1.2.3.4,
>         file.server.0.port=24007,
>         file.server.1.type=tcp,
>         file.server.1.socket=/var/run/glusterd.socket
> 2.
>  'json:{"driver":"qcow2","file":{"driver":"gluster","volume":"testvol",
>          "path":"/path/a.qcow2","debug":9,"server":
>          [{type:"tcp",host:"1.2.3.4",port=24007},
>           {type:"unix",socket:"/var/run/glusterd.socket"}] } }'

This example is 1. confusing, and 2. wrong :)

It's wrong, because several member names lack quotes.  Also, the value
of port should be a string.

It confused me, because I didn't realize that this is the non-option
image argument.  Two ways to fix that.  One, add context:

    $ qemu-system-x86_64 
'json:{"file":{"driver":"gluster","volume":"sample","path":"/fedora23.qcow2","server":[{"type":"tcp","host":"192.168.1.220","port":"24007"},{"type":"unix","socket":"/var/run/glusterd.socket"}]},"driver":"qcow2"}'

Two, use -drive:

    -drive 
'file=json:{"file":{"driver":"gluster",,"volume":"sample",,"path":"/fedora23.qcow2",,"server":[{"type":"tcp",,"host":"192.168.1.220",,"port":"24007"},,{"type":"unix",,"socket":"/var/run/glusterd.socket"}]},,"driver":"qcow2"}'

Exquisitely ugly due to the necessary comma escaping.

Hopefully, the maintainer can touch this up on commit.

> 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 all the supporters
>
> Signed-off-by: Prasanna Kumar Kalever <address@hidden>

R-by stands.