Re: [Qemu-devel] [PATCH v19 5/5] block/gluster: add support for multiple gluster servers

[Markus Armbruster]

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. (default 24007)
>    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 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>
> ---
>  block/gluster.c      | 347 
> +++++++++++++++++++++++++++++++++++++++++++++------
>  qapi/block-core.json |   2 +-
>  2 files changed, 307 insertions(+), 42 deletions(-)
>
> diff --git a/block/gluster.c b/block/gluster.c
> index ff1e783..fd2279d 100644
> --- a/block/gluster.c
> +++ b/block/gluster.c
> @@ -12,8 +12,16 @@
>  #include "block/block_int.h"
>  #include "qapi/error.h"
>  #include "qemu/uri.h"
> +#include "qemu/error-report.h"
>  
>  #define GLUSTER_OPT_FILENAME        "filename"
> +#define GLUSTER_OPT_VOLUME          "volume"
> +#define GLUSTER_OPT_PATH            "path"
> +#define GLUSTER_OPT_TYPE            "type"
> +#define GLUSTER_OPT_SERVER_PATTERN  "server."
> +#define GLUSTER_OPT_HOST            "host"
> +#define GLUSTER_OPT_PORT            "port"
> +#define GLUSTER_OPT_SOCKET          "socket"
>  #define GLUSTER_OPT_DEBUG           "debug"
>  #define GLUSTER_DEFAULT_PORT        24007
>  #define GLUSTER_DEBUG_DEFAULT       4
> @@ -82,6 +90,77 @@ static QemuOptsList runtime_opts = {
>      },
>  };
>  
> +static QemuOptsList runtime_json_opts = {
> +    .name = "gluster_json",
> +    .head = QTAILQ_HEAD_INITIALIZER(runtime_json_opts.head),
> +    .desc = {
> +        {
> +            .name = GLUSTER_OPT_VOLUME,
> +            .type = QEMU_OPT_STRING,
> +            .help = "name of gluster volume where VM image resides",
> +        },
> +        {
> +            .name = GLUSTER_OPT_PATH,
> +            .type = QEMU_OPT_STRING,
> +            .help = "absolute path to image file in gluster volume",
> +        },
> +        {
> +            .name = GLUSTER_OPT_DEBUG,
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "Gluster log level, valid range is 0-9",
> +        },
> +        { /* end of list */ }
> +    },
> +};
> +
> +static QemuOptsList runtime_type_opts = {
> +    .name = "gluster_type",
> +    .head = QTAILQ_HEAD_INITIALIZER(runtime_type_opts.head),
> +    .desc = {
> +        {
> +            .name = GLUSTER_OPT_TYPE,
> +            .type = QEMU_OPT_STRING,
> +            .help = "tcp|unix",
> +        },
> +        { /* end of list */ }
> +    },
> +};
> +
> +static QemuOptsList runtime_unix_opts = {
> +    .name = "gluster_unix",
> +    .head = QTAILQ_HEAD_INITIALIZER(runtime_unix_opts.head),
> +    .desc = {
> +        {
> +            .name = GLUSTER_OPT_SOCKET,
> +            .type = QEMU_OPT_STRING,
> +            .help = "socket file path)",
> +        },
> +        { /* end of list */ }
> +    },
> +};
> +
> +static QemuOptsList runtime_tcp_opts = {
> +    .name = "gluster_tcp",
> +    .head = QTAILQ_HEAD_INITIALIZER(runtime_tcp_opts.head),
> +    .desc = {
> +        {
> +            .name = GLUSTER_OPT_TYPE,
> +            .type = QEMU_OPT_STRING,
> +            .help = "tcp|unix",
> +        },
> +        {
> +            .name = GLUSTER_OPT_HOST,
> +            .type = QEMU_OPT_STRING,
> +            .help = "host address (hostname/ipv4/ipv6 addresses)",
> +        },
> +        {
> +            .name = GLUSTER_OPT_PORT,
> +            .type = QEMU_OPT_NUMBER,
> +            .help = "port number on which glusterd is listening (default 
> 24007)",
> +        },
> +        { /* end of list */ }
> +    },
> +};
>  
>  static int parse_volume_options(BlockdevOptionsGluster *gconf, char *path)
>  {
> @@ -157,7 +236,8 @@ static int qemu_gluster_parse_uri(BlockdevOptionsGluster 
> *gconf,
>          return -EINVAL;
>      }
>  
> -    gconf->server = gsconf = g_new0(GlusterServer, 1);
> +    gconf->server = g_new0(GlusterServerList, 1);
> +    gconf->server->value = gsconf = g_new0(GlusterServer, 1);
>  
>      /* transport */
>      if (!uri->scheme || !strcmp(uri->scheme, "gluster")) {
> @@ -211,38 +291,34 @@ out:
>      return ret;
>  }
>  
> -static struct glfs *qemu_gluster_init(BlockdevOptionsGluster *gconf,
> -                                      const char *filename, Error **errp)
> +static struct glfs *qemu_gluster_glfs_init(BlockdevOptionsGluster *gconf,
> +                                           Error **errp)
>  {
> -    struct glfs *glfs = NULL;
> +    struct glfs *glfs;
>      int ret;
>      int old_errno;
> -
> -    ret = qemu_gluster_parse_uri(gconf, filename);
> -    if (ret < 0) {
> -        error_setg(errp, "Usage: file=gluster[+transport]://[host[:port]]/"
> -                         "volume/path[?socket=...]");
> -        errno = -ret;
> -        goto out;
> -    }
> +    GlusterServerList *server;
>  
>      glfs = glfs_new(gconf->volume);
>      if (!glfs) {
>          goto out;
>      }
>  
> -    if (gconf->server->type == GLUSTER_TRANSPORT_UNIX) {
> -        ret = glfs_set_volfile_server(glfs,
> -                                      
> GlusterTransport_lookup[gconf->server->type],
> -                                      gconf->server->u.q_unix.socket, 0);
> -    } else {
> -        ret = glfs_set_volfile_server(glfs,
> -                                      
> GlusterTransport_lookup[gconf->server->type],
> -                                      gconf->server->u.tcp.host,
> -                                      gconf->server->u.tcp.port);
> -    }
> -    if (ret < 0) {
> -        goto out;
> +    for (server = gconf->server; server; server = server->next) {
> +        if (server->value->type  == GLUSTER_TRANSPORT_UNIX) {
> +            ret = glfs_set_volfile_server(glfs,
> +                                          
> GlusterTransport_lookup[server->value->type],
> +                                          server->value->u.q_unix.socket, 0);
> +        } else {
> +            ret = glfs_set_volfile_server(glfs,
> +                                          
> GlusterTransport_lookup[server->value->type],
> +                                          server->value->u.tcp.host,
> +                                          server->value->u.tcp.port);

server->value.u.tcp.port is optional.  Using it without checking
server->value.u.tcp.has_port relies on the default value being zero.  We
don't actually document that.  Perhaps we should.

> +        }
> +
> +        if (ret < 0) {
> +            goto out;
> +        }
>      }
>  
>      ret = glfs_set_logging(glfs, "-", gconf->debug_level);
> @@ -252,19 +328,19 @@ static struct glfs 
> *qemu_gluster_init(BlockdevOptionsGluster *gconf,
>  
>      ret = glfs_init(glfs);
>      if (ret) {
> -        if (gconf->server->type == GLUSTER_TRANSPORT_UNIX) {
> -            error_setg(errp,
> -                       "Gluster connection for volume: %s, path: %s "
> -                       "failed to connect on socket %s ",
> -                       gconf->volume, gconf->path,
> -                       gconf->server->u.q_unix.socket);
> -        } else {
> -            error_setg(errp,
> -                       "Gluster connection for volume: %s, path: %s "
> -                       "failed to connect  host  %s and port %d ",
> -                       gconf->volume, gconf->path,
> -                       gconf->server->u.tcp.host, gconf->server->u.tcp.port);
> +        error_setg(errp, "Gluster connection for volume: %s, path: %s ",
> +                   gconf->volume, gconf->path);
> +        for (server = gconf->server; server; server = server->next) {
> +            if (server->value->type  == GLUSTER_TRANSPORT_UNIX) {
> +                error_append_hint(errp, "failed to connect on socket %s ",
> +                                  server->value->u.q_unix.socket);
> +            } else {
> +                error_append_hint(errp, "failed to connect host %s and port 
> %d ",
> +                                  server->value->u.tcp.host,
> +                                  server->value->u.tcp.port);
> +            }
>          }
> +        error_append_hint(errp, "Please refer to gluster logs for more info 
> ");

Your code produces the error message "Gluster connection for volume:
VOLUME, path: PATH ", which makes no sense.

It also produces a hint that is a concatenation of one or more "failed
to connect on FOO", followed by "Please refer to ..." without any
punctuation, but with a trailing space.

The error message must make sense on its own, without the hint.

A fixed error message could look like this:

    Gluster connection for volume VOLUME, path PATH failed to connect on FOO, 
on BAR, and on BAZ

or with a little less effort

    Gluster connection for volume VOLUME, path PATH failed to connect on FOO, 
BAR, BAZ

or simply

    Can't connect to Gluster volume VOLUME, path PATH at FOO, BAR, BAZ

You can't build up the error message with error_append_hint().  Using it
to append a hint pointing to Gluster logs is fine.

>  
>          /* glfs_init sometimes doesn't set errno although docs suggest that 
> */
>          if (errno == 0) {
> @@ -284,6 +360,195 @@ out:
>      return NULL;
>  }
>  
> +static int qapi_enum_parse(const char *opt)
> +{
> +    int i;
> +
> +    if (!opt) {
> +        return GLUSTER_TRANSPORT__MAX;
> +    }
> +
> +    for (i = 0; i < GLUSTER_TRANSPORT__MAX; i++) {
> +        if (!strcmp(opt, GlusterTransport_lookup[i])) {
> +            return i;
> +        }
> +    }
> +
> +    return i;
> +}
> +
> +/*
> + * Convert the json formatted command line into qapi.
> +*/
> +static int qemu_gluster_parse_json(BlockdevOptionsGluster *gconf,
> +                                  QDict *options, Error **errp)
> +{
> +    QemuOpts *opts;
> +    GlusterServer *gsconf;
> +    GlusterServerList *curr = NULL;
> +    QDict *backing_options = NULL;
> +    Error *local_err = NULL;
> +    char *str = NULL;
> +    const char *ptr;
> +    size_t num_servers;
> +    int i;
> +
> +    /* create opts info from runtime_json_opts list */
> +    opts = qemu_opts_create(&runtime_json_opts, NULL, 0, &error_abort);
> +    qemu_opts_absorb_qdict(opts, options, &local_err);
> +    if (local_err) {
> +        goto out;
> +    }
> +
> +    num_servers = qdict_array_entries(options, GLUSTER_OPT_SERVER_PATTERN);
> +    if (num_servers < 1) {
> +        error_setg(&local_err, "please provide 'server' option with valid "
> +                               "fields in array of hostinfo ");

This isn't an error message, it's instructions what to do.  Such
instructions can be useful when they're correct, but they can't replace
an error message.  The error message should state what's wrong.  No
less, no more.

Moreover, avoid prefixes like "qemu_gluster:".  Usually, the fact that
this is about Gluster is obvious.  When it isn't, providing context is
the caller's job.

> +        goto out;
> +    }
> +
> +    ptr = qemu_opt_get(opts, GLUSTER_OPT_VOLUME);
> +    if (!ptr) {
> +        error_setg(&local_err, "please provide 'volume' option ");

Not an error message.

> +        goto out;
> +    }
> +    gconf->volume = g_strdup(ptr);
> +
> +    ptr = qemu_opt_get(opts, GLUSTER_OPT_PATH);
> +    if (!ptr) {
> +        error_setg(&local_err, "please provide 'path' option ");

Not an error message.

> +        goto out;
> +    }
> +    gconf->path = g_strdup(ptr);
> +    qemu_opts_del(opts);
> +
> +    for (i = 0; i < num_servers; i++) {
> +        str = g_strdup_printf(GLUSTER_OPT_SERVER_PATTERN"%d.", i);
> +        qdict_extract_subqdict(options, &backing_options, str);
> +
> +        /* create opts info from runtime_type_opts list */
> +        opts = qemu_opts_create(&runtime_type_opts, NULL, 0, &error_abort);
> +        qemu_opts_absorb_qdict(opts, backing_options, &local_err);
> +        if (local_err) {
> +            goto out;
> +        }
> +
> +        ptr = qemu_opt_get(opts, GLUSTER_OPT_TYPE);
> +        gsconf = g_new0(GlusterServer, 1);
> +        gsconf->type = qapi_enum_parse(ptr);
> +        if (!ptr) {
> +            error_setg(&local_err, "please provide 'type' in hostinfo.%d as "
> +                                   "tcp|unix ", i);

Not an error message.

> +            goto out;
> +
> +        }
> +        if (gsconf->type == GLUSTER_TRANSPORT__MAX) {
> +            error_setg(&local_err, "'type' in hostinfo.%d can be tcp|unix ", 
> i);
> +            goto out;
> +        }
> +        qemu_opts_del(opts);
> +
> +        if (gsconf->type == GLUSTER_TRANSPORT_TCP) {
> +            /* create opts info from runtime_tcp_opts list */
> +            opts = qemu_opts_create(&runtime_tcp_opts, NULL, 0, 
> &error_abort);
> +            qemu_opts_absorb_qdict(opts, backing_options, &local_err);
> +            if (local_err) {
> +                goto out;
> +            }
> +
> +            ptr = qemu_opt_get(opts, GLUSTER_OPT_HOST);
> +            if (!ptr) {
> +                error_setg(&local_err, "please provide 'host' in hostinfo.%d 
> ",
> +                           i);
> +                goto out;
> +            }
> +            gsconf->u.tcp.host = g_strdup(ptr);
> +            ptr = qemu_opt_get(opts, GLUSTER_OPT_PORT);
> +            gsconf->u.tcp.port = qemu_opt_get_number(opts, GLUSTER_OPT_PORT,
> +                                               GLUSTER_DEFAULT_PORT);
> +            gsconf->u.tcp.has_port = true;
> +            qemu_opts_del(opts);
> +        } else {
> +            /* create opts info from runtime_unix_opts list */
> +            opts = qemu_opts_create(&runtime_unix_opts, NULL, 0, 
> &error_abort);
> +            qemu_opts_absorb_qdict(opts, backing_options, &local_err);
> +            if (local_err) {
> +                goto out;
> +            }
> +
> +            ptr = qemu_opt_get(opts, GLUSTER_OPT_SOCKET);
> +            if (!ptr) {
> +                error_setg(&local_err, "please provide 'socket' in 
> hostinfo.%d ",
> +                           i);
> +                goto out;
> +            }
> +            gsconf->u.q_unix.socket = g_strdup(ptr);
> +            qemu_opts_del(opts);
> +        }
> +
> +        if (gconf->server == NULL) {
> +            gconf->server = g_new0(GlusterServerList, 1);
> +            gconf->server->value = gsconf;
> +            curr = gconf->server;
> +        } else {
> +            curr->next = g_new0(GlusterServerList, 1);
> +            curr->next->value = gsconf;
> +            curr = curr->next;
> +        }
> +
> +        qdict_del(backing_options, str);
> +        g_free(str);
> +        str = NULL;
> +    }
> +
> +    return 0;
> +
> +out:
> +    if (local_err) {
> +        error_propagate(errp, local_err);
> +    }

error_propagate() does the right thing when its second argument is
null.  Please drop the conditional.

> +    qemu_opts_del(opts);
> +    if (str) {
> +        qdict_del(backing_options, str);
> +        g_free(str);
> +    }
> +    errno = EINVAL;
> +    return -errno;
> +}
> +
> +static struct glfs *qemu_gluster_init(BlockdevOptionsGluster *gconf,
> +                                      const char *filename,
> +                                      QDict *options, Error **errp)
> +{
> +    int ret;
> +    if (filename) {
> +        ret = qemu_gluster_parse_uri(gconf, filename);
> +        if (ret < 0) {
> +            error_setg(errp, "Usage: 
> file=gluster[+transport]://[host[:port]]/"
> +                             "volume/path[?socket=...]");

Not an error message.

> +            errno = -ret;
> +            return NULL;
> +        }
> +    } else {
> +        ret = qemu_gluster_parse_json(gconf, options, errp);
> +        if (ret < 0) {
> +            error_append_hint(errp, "Usage: "
> +                             "-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.transport=unix,"
> +                             "file.server.1.socket=/var/run/glusterd.socket 
> ...");
> +            errno = -ret;
> +            return NULL;
> +        }
> +
> +    }
> +
> +    return qemu_gluster_glfs_init(gconf, errp);
> +}
> +
>  static void qemu_gluster_complete_aio(void *opaque)
>  {
>      GlusterAIOCB *acb = (GlusterAIOCB *)opaque;
> @@ -383,7 +648,7 @@ static int qemu_gluster_open(BlockDriverState *bs,  QDict 
> *options,
>      gconf = g_new0(BlockdevOptionsGluster, 1);
>      gconf->debug_level = s->debug_level;
>      gconf->has_debug_level = true;
> -    s->glfs = qemu_gluster_init(gconf, filename, errp);
> +    s->glfs = qemu_gluster_init(gconf, filename, options, errp);
>      if (!s->glfs) {
>          ret = -errno;
>          goto out;
> @@ -454,7 +719,7 @@ static int qemu_gluster_reopen_prepare(BDRVReopenState 
> *state,
>      gconf = g_new0(BlockdevOptionsGluster, 1);
>      gconf->debug_level = s->debug_level;
>      gconf->has_debug_level = true;
> -    reop_s->glfs = qemu_gluster_init(gconf, state->bs->filename, errp);
> +    reop_s->glfs = qemu_gluster_init(gconf, state->bs->filename, NULL, errp);
>      if (reop_s->glfs == NULL) {
>          ret = -errno;
>          goto exit;
> @@ -601,7 +866,7 @@ static int qemu_gluster_create(const char *filename,
>      }
>      gconf->has_debug_level = true;
>  
> -    glfs = qemu_gluster_init(gconf, filename, errp);
> +    glfs = qemu_gluster_init(gconf, filename, NULL, errp);
>      if (!glfs) {
>          ret = -errno;
>          goto out;
> @@ -981,7 +1246,7 @@ static BlockDriver bdrv_gluster = {
>      .format_name                  = "gluster",
>      .protocol_name                = "gluster",
>      .instance_size                = sizeof(BDRVGlusterState),
> -    .bdrv_needs_filename          = true,
> +    .bdrv_needs_filename          = false,
>      .bdrv_file_open               = qemu_gluster_open,
>      .bdrv_reopen_prepare          = qemu_gluster_reopen_prepare,
>      .bdrv_reopen_commit           = qemu_gluster_reopen_commit,
> @@ -1009,7 +1274,7 @@ static BlockDriver bdrv_gluster_tcp = {
>      .format_name                  = "gluster",
>      .protocol_name                = "gluster+tcp",
>      .instance_size                = sizeof(BDRVGlusterState),
> -    .bdrv_needs_filename          = true,
> +    .bdrv_needs_filename          = false,
>      .bdrv_file_open               = qemu_gluster_open,
>      .bdrv_reopen_prepare          = qemu_gluster_reopen_prepare,
>      .bdrv_reopen_commit           = qemu_gluster_reopen_commit,
> diff --git a/qapi/block-core.json b/qapi/block-core.json
> index d7b5c76..5557f1c 100644
> --- a/qapi/block-core.json
> +++ b/qapi/block-core.json
> @@ -2137,7 +2137,7 @@
>  { 'struct': 'BlockdevOptionsGluster',
>    'data': { 'volume': 'str',
>              'path': 'str',
> -            'server': 'GlusterServer',
> +            'server': ['GlusterServer'],
>              '*debug_level': 'int' } }
>  
>  ##