Re: [Qemu-devel] [PATCH V7 11/17] qapi: Add new command to query colo status

[Markus Armbruster <armbru@redhat.com>]

Zhang Chen <zhangckid@gmail.com> writes:

> Libvirt or other high level software can use this command query colo status.
> You can test this command like that:
> {'execute':'query-colo-status'}
>
> Signed-off-by: Zhang Chen <zhangckid@gmail.com>
> ---
>  migration/colo.c    | 34 ++++++++++++++++++++++++++++++++++
>  qapi/migration.json | 33 +++++++++++++++++++++++++++++++++
>  2 files changed, 67 insertions(+)
>
> diff --git a/migration/colo.c b/migration/colo.c
> index 8ca6381..314344c 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -29,6 +29,7 @@
>  #include "net/colo.h"
>  #include "block/block.h"
>  #include "qapi/qapi-events-migration.h"
> +#include "qapi/qmp/qerror.h"
>  
>  static bool vmstate_loading;
>  static Notifier packets_compare_notifier;
> @@ -237,6 +238,39 @@ void qmp_xen_colo_do_checkpoint(Error **errp)
>  #endif
>  }
>  
> +COLOStatus *qmp_query_colo_status(Error **errp)
> +{
> +    int state;
> +    COLOStatus *s = g_new0(COLOStatus, 1);
> +
> +    if (get_colo_mode() == COLO_MODE_UNKNOWN) {
> +        error_setg(errp, QERR_FEATURE_DISABLED, "colo");
> +        s->colo_running = false;
> +        goto out;
> +    } else if (get_colo_mode() == COLO_MODE_PRIMARY) {
> +         state = migrate_get_current()->state;
> +    } else {
> +         state = migration_incoming_get_current()->state;
> +    }

Indentation's off, as patchew pointed out.  Perhaps the maintainer could
fix that for you.

> +    s->colo_running = state == MIGRATION_STATUS_COLO;
> +
> +out:
> +    s->mode = get_colo_mode();

I'm okay with this.

If you need to respin anyway, consider whether you like this better:

       s->mode = get_colo_mode();
       switch (s->mode) {
       case COLO_MODE_UNKNOWN:
           error_setg(errp, "COLO is disabled");
           state = MIGRATION_STATUS_NONE;
           break;
       case COLO_MODE_PRIMARY:
           state = migrate_get_current()->state;
           break;
       case COLO_MODE_SECONDARY:
           state = migration_incoming_get_current()->state;
           break;
       default:
           abort();
       }
       s->colo_running = state == MIGRATION_STATUS_COLO;

Aside: we should really finish off the QERR_ macros.

> +
> +    switch (failover_get_state()) {
> +    case FAILOVER_STATUS_NONE:
> +        s->reason = COLO_EXIT_REASON_NONE;
> +        break;
> +    case FAILOVER_STATUS_REQUIRE:
> +        s->reason = COLO_EXIT_REASON_REQUEST;
> +        break;
> +    default:
> +        s->reason = COLO_EXIT_REASON_ERROR;
> +    }
> +
> +    return s;
> +}
> +
>  static void colo_send_message(QEMUFile *f, COLOMessage msg,
>                                Error **errp)
>  {
> diff --git a/qapi/migration.json b/qapi/migration.json
> index 55dae48..13589ba 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -1220,3 +1220,36 @@
>  # Since: 2.9
>  ##
>  { 'command': 'xen-colo-do-checkpoint' }
> +
> +##
> +# @COLOStatus:
> +#
> +# The result format for 'query-colo-status'.
> +#
> +# @mode: which COLO mode the VM was in when it exited.

Pardon my COLO-ignorance...

What does "when it exited" mean?

What's the value of @mode before "it exited"?

> +# @colo-running: true if COLO is running.

If COLO is running, has "it exited", yet?

> +#
> +# @reason: describes the reason for the COLO exit.

What's the value of @reason before a "COLO exit"?

Remember, while a COLO_EXIT event is tied to an exit, a
query-colo-status can be executed at any time, in particular before any
"COLO exit".

> +#
> +# Since: 2.13
> +##
> +{ 'struct': 'COLOStatus',
> +  'data': { 'mode': 'COLOMode', 'colo-running': 'bool', 'reason': 'COLOExitReason' } }
> +
> +##
> +# @query-colo-status:
> +#
> +# Query COLO status while the vm is running.
> +#
> +# Returns: A @COLOStatus object showing the status.
> +#
> +# Example:
> +#
> +# -> { "execute": "query-colo-status" }
> +# <- { "return": { "mode": "primary", "colo-running": true, "reason": "request" } }
> +#
> +# Since: 2.13
> +##
> +{ 'command': 'query-colo-status',
> +  'returns': 'COLOStatus' }

Almost ready :)