Re: [Qemu-devel] [PATCH RFC v3 24/27] COLO NIC: Implement NIC checkpoint and failover

["Dr. David Alan Gilbert" <dgilbert@redhat.com>]

* zhanghailiang (zhang.zhanghailiang@huawei.com) wrote:
> Signed-off-by: zhanghailiang <zhang.zhanghailiang@huawei.com>
> Signed-off-by: Gao feng <gaofeng@cn.fujitsu.com>
> ---
>  include/net/colo-nic.h |  3 ++-
>  migration/colo.c       | 22 ++++++++++++++++++----
>  net/colo-nic.c         | 19 +++++++++++++++++++
>  3 files changed, 39 insertions(+), 5 deletions(-)
> 
> diff --git a/include/net/colo-nic.h b/include/net/colo-nic.h
> index 67c9807..ddc21cd 100644
> --- a/include/net/colo-nic.h
> +++ b/include/net/colo-nic.h
> @@ -20,5 +20,6 @@ void colo_add_nic_devices(NetClientState *nc);
>  void colo_remove_nic_devices(NetClientState *nc);
>  
>  int colo_proxy_compare(void);
> -
> +int colo_proxy_failover(void);
> +int colo_proxy_checkpoint(void);
>  #endif
> diff --git a/migration/colo.c b/migration/colo.c
> index 579aabf..874971c 100644
> --- a/migration/colo.c
> +++ b/migration/colo.c
> @@ -94,6 +94,11 @@ static void slave_do_failover(void)
>          ;
>      }
>  
> +    if (colo_proxy_failover() != 0) {
> +        error_report("colo proxy failed to do failover");
> +    }
> +    colo_proxy_destroy(COLO_SECONDARY_MODE);

I'm not sure if this is the best thing to do on a secondary failover.
If I understand correctly, when it's running, we have:


-------+
       |                    br0---eth0
       |
 slave +-tun - xt_SECCOLO - br1---eth1
       |
-------+

what I think that colo-proxy-destroy  is doing is rewiring that as:


-------+
       |     +--------------br0---eth0
       |     |
 slave +-tun +              br1---eth1
       |
-------+

but now we've lost the sequence number adjustment data that
was held in xt_SECCOLO and so you are likely to break existing TCP
connections.

Also, I don't think colo-proxy-script is passed a flag to let it
know whether the reason it's doing a slave_uninstall is due to
a failover or a simple shutdown; and so it assumes it has
to do the rewire for a failover.
(Actually the script in the qemu repo is newer than the script in
the colo-proxy repo, that one doesn't have the rewire at all).

Dave

> +
>      colo = NULL;
>  
>      if (!autostart) {
> @@ -115,7 +120,7 @@ static void master_do_failover(void)
>      if (!colo_runstate_is_stopped()) {
>          vm_stop_force_state(RUN_STATE_COLO);
>      }
> -
> +    colo_proxy_destroy(COLO_PRIMARY_MODE);
>      if (s->state != MIG_STATE_ERROR) {
>          migrate_set_state(s, MIG_STATE_COLO, MIG_STATE_COMPLETED);
>      }
> @@ -245,6 +250,11 @@ static int do_colo_transaction(MigrationState *s, QEMUFile *control)
>  
>      qemu_fflush(trans);
>  
> +    ret = colo_proxy_checkpoint();
> +    if (ret < 0) {
> +        goto out;
> +    }
> +
>      ret = colo_ctl_put(s->file, COLO_CHECKPOINT_SEND);
>      if (ret < 0) {
>          goto out;
> @@ -387,8 +397,6 @@ out:
>      qemu_bh_schedule(s->cleanup_bh);
>      qemu_mutex_unlock_iothread();
>  
> -    colo_proxy_destroy(COLO_PRIMARY_MODE);
> -
>      return NULL;
>  }
>  
> @@ -508,6 +516,12 @@ void *colo_process_incoming_checkpoints(void *opaque)
>              goto out;
>          }
>  
> +        ret = colo_proxy_checkpoint();
> +        if (ret < 0) {
> +                goto out;
> +        }
> +        DPRINTF("proxy begin to do checkpoint\n");
> +
>          ret = colo_ctl_get(f, COLO_CHECKPOINT_SEND);
>          if (ret < 0) {
>              goto out;
> @@ -584,6 +598,7 @@ out:
>          * just kill slave
>          */
>          error_report("SVM is going to exit!");
> +        colo_proxy_destroy(COLO_SECONDARY_MODE);
>          exit(1);
>      } else {
>          /* if we went here, means master may dead, we are doing failover */
> @@ -610,6 +625,5 @@ out:
>  
>      loadvm_exit_colo();
>  
> -    colo_proxy_destroy(COLO_SECONDARY_MODE);
>      return NULL;
>  }
> diff --git a/net/colo-nic.c b/net/colo-nic.c
> index 563d661..02a454d 100644
> --- a/net/colo-nic.c
> +++ b/net/colo-nic.c
> @@ -379,6 +379,25 @@ void colo_proxy_destroy(int side)
>      cp_info.index = -1;
>      colo_nic_side = -1;
>  }
> +
> +int colo_proxy_failover(void)
> +{
> +    if (colo_proxy_send(NULL, 0, COLO_FAILOVER) < 0) {
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
> +int colo_proxy_checkpoint(void)
> +{
> +    if (colo_proxy_send(NULL, 0, COLO_CHECKPOINT) < 0) {
> +        return -1;
> +    }
> +
> +    return 0;
> +}
> +
>  /*
>  do checkpoint: return 1
>  error: return -1
> -- 
> 1.7.12.4
> 
> 
--
Dr. David Alan Gilbert / dgilbert@redhat.com / Manchester, UK