Re: [Qemu-devel] [PATCH V7 10/17] qmp event: Add COLO_EXIT event to notify users while exited COLO

[Markus Armbruster]

Zhang Chen <address@hidden> writes:

> From: zhanghailiang <address@hidden>
>
> If some errors happen during VM's COLO FT stage, it's important to
> notify the users of this event. Together with 'x-colo-lost-heartbeat',
> Users can intervene in COLO's failover work immediately.
> If users don't want to get involved in COLO's failover verdict,
> it is still necessary to notify users that we exited COLO mode.
>
> Signed-off-by: zhanghailiang <address@hidden>
> Signed-off-by: Li Zhijian <address@hidden>
> Signed-off-by: Zhang Chen <address@hidden>
> Reviewed-by: Eric Blake <address@hidden>
> ---
>  migration/colo.c    | 20 ++++++++++++++++++++
>  qapi/migration.json | 37 +++++++++++++++++++++++++++++++++++++
>  2 files changed, 57 insertions(+)
>
> diff --git a/migration/colo.c b/migration/colo.c
> index c083d36..8ca6381 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -28,6 +28,7 @@
>  #include "net/colo-compare.h"
>  #include "net/colo.h"
>  #include "block/block.h"
> +#include "qapi/qapi-events-migration.h"
>  
>  static bool vmstate_loading;
>  static Notifier packets_compare_notifier;
> @@ -514,6 +515,18 @@ out:
>          qemu_fclose(fb);
>      }
>  
> +    /*
> +     * There are only two reasons we can go here, some error happened.
> +     * Or the user triggered failover.
> +     */
> +    if (failover_get_state() == FAILOVER_STATUS_NONE) {
> +        qapi_event_send_colo_exit(COLO_MODE_PRIMARY,
> +                                  COLO_EXIT_REASON_ERROR, NULL);
> +    } else {
> +        qapi_event_send_colo_exit(COLO_MODE_PRIMARY,
> +                                  COLO_EXIT_REASON_REQUEST, NULL);
> +    }

Your comment makes me suspect failover_get_state() can only be
FAILOVER_STATUS_NONE or FAILOVER_STATUS_REQUIRE here.  Is that correct?

If yes, I recommend to add a suitable assertion.

> +
>      /* Hope this not to be too long to wait here */
>      qemu_sem_wait(&s->colo_exit_sem);
>      qemu_sem_destroy(&s->colo_exit_sem);
> @@ -744,6 +757,13 @@ out:
>      if (local_err) {
>          error_report_err(local_err);
>      }
> +    if (failover_get_state() == FAILOVER_STATUS_NONE) {
> +        qapi_event_send_colo_exit(COLO_MODE_SECONDARY,
> +                                  COLO_EXIT_REASON_ERROR, NULL);
> +    } else {
> +        qapi_event_send_colo_exit(COLO_MODE_SECONDARY,
> +                                  COLO_EXIT_REASON_REQUEST, NULL);
> +    }

Same question.

>  
>      if (fb) {
>          qemu_fclose(fb);
> diff --git a/qapi/migration.json b/qapi/migration.json
> index f3974c6..55dae48 100644
> --- a/qapi/migration.json
> +++ b/qapi/migration.json
> @@ -875,6 +875,43 @@
>    'data': [ 'none', 'require', 'active', 'completed', 'relaunch' ] }
>  
>  ##
> +# @COLO_EXIT:
> +#
> +# Emitted when VM finishes COLO mode due to some errors happening or
> +# at the request of users.
> +#
> +# @mode: report COLO mode when COLO exited.
> +#
> +# @reason: describes the reason for the COLO exit.
> +#
> +# Since: 2.13
> +#
> +# Example:
> +#
> +# <- { "timestamp": {"seconds": 2032141960, "microseconds": 417172},
> +#      "event": "COLO_EXIT", "data": {"mode": "primary", "reason": "request" 
> } }
> +#
> +##
> +{ 'event': 'COLO_EXIT',
> +  'data': {'mode': 'COLOMode', 'reason': 'COLOExitReason' } }

'data' duplicates the next patch's ColoStatus, except it lacks
@colo-running.  Factoring out the common part doesn't seem worth the
bother.  Okay as is.

> +
> +##
> +# @COLOExitReason:
> +#
> +# The reason for a COLO exit
> +#
> +# @none: no failover has ever happened.

This can't occur in the COLO_EXIT event, only in the result of
query-colo-status, can it?

Worth spelling that out in the documentation?

> +#
> +# @request: COLO exit is due to an external request
> +#
> +# @error: COLO exit is due to an internal error
> +#
> +# Since: 2.13
> +##
> +{ 'enum': 'COLOExitReason',
> +  'data': [ 'none', 'request', 'error' ] }
> +
> +##
>  # @x-colo-lost-heartbeat:
>  #
>  # Tell qemu that heartbeat is lost, request it to do takeover procedures.