[Sheepdog] PATCH S003: Handle master crashing before sending JOIN request

[MORITA Kazutaka]

At Mon, 30 Apr 2012 18:47:54 +0800,
Liu Yuan wrote:
> 
> On Mon, Apr 30, 2012 at 5:23 PM, MORITA Kazutaka
> <morita.kazutaka at gmail.com> wrote:
> > At Sun, 29 Apr 2012 02:05:33 +0800,
> > Liu Yuan wrote:
> >>
> >> No, your patch is completely wrong workaround, not a fix. You just set
> >> every node as 'first node' and all nodes become the master and send the
> >> response to each other.
> >
> > I think you misunderstand Shevek's patch.  IIUC, there is no situation
> > that multiple nodes become the master at the same time with his patch.
> >
> > Shevek's patch is relatively straightforward.  If you think it is
> > hacky, what should be blamed is 'first_node' in the corosync_event
> > structure, which is introduced by me.
> >
> > I like Christoph's version:
> >  http://lists.wpkg.org/pipermail/sheepdog/2012-April/003186.html
> > Yuan, what do you think of it?
> >
> 
> Okay, I think Christoph's patch is easier to understand, I am fine
> with it, but it needs following changes:
> 
> diff --git a/sheep/cluster/corosync.c b/sheep/cluster/corosync.c
> index b22ed87..2d73038 100644
> --- a/sheep/cluster/corosync.c
> +++ b/sheep/cluster/corosync.c
> @@ -37,6 +37,7 @@ static LIST_HEAD(corosync_block_list);
>  static struct cpg_node cpg_nodes[SD_MAX_NODES];
>  static size_t nr_cpg_nodes;
>  static int self_elect;
> +static int join_finished;
> 
>  /* event types which are dispatched in corosync_dispatch() */
>  enum corosync_event_type {
> @@ -378,7 +379,6 @@ static int __corosync_dispatch_one(struct
> corosync_event *cevent)
>  static void __corosync_dispatch(void)
>  {
>  	struct corosync_event *cevent;
> -	static int join_finished;
>  	int done;
> 
>  	while (!list_empty(&corosync_event_list)) {
> @@ -620,27 +620,29 @@ static void cdrv_cpg_confchg(cpg_handle_t handle,
>  		list_add_tail(&cevent->list, &corosync_event_list);
>  	}
> 
> -	/*
> -	 * Exactly one non-master member has seen join events for all other
> -	 * members, because events are ordered.
> -	 */
> -	for (i = 0; i < member_list_entries; i++) {
> -		cevent = find_block_event(COROSYNC_EVENT_TYPE_JOIN,
> -					  &member_sheep[i]);
> -		if (!cevent) {
> -			dprintf("Not promoting because member is not in our "
> -				"event list.\n");
> -			promote = 0;
> +	if (!join_finished) {
> +		/*
> +		 * Exactly one non-master member has seen join events for all other
> +		 * members, because events are ordered.
> +		 */
> +		for (i = 0; i < member_list_entries; i++) {
> +			cevent = find_block_event(COROSYNC_EVENT_TYPE_JOIN,
> +					&member_sheep[i]);
> +			if (!cevent) {
> +				dprintf("Not promoting because member is not in our "
> +						"event list.\n");
> +				promote = 0;
> +				break;
> +			}
>  		}
> -	}
> -
> -	/*
> -	 * If we see the join events for all nodes promote ourself to master
> -	 * right here.
> -	 */
> -	if (promote)
> -		self_elect = 1;
> 
> +		/*
> +		 * If we see the join events for all nodes promote ourself to master
> +		 * right here.
> +		 */
> +		if (promote)
> +			self_elect = 1;
> +	}
>  	__corosync_dispatch();
>  }
> 
> These changes are needed, because only those nodes, that aren't
> join_finished, are legitimate to do self-elect. or we are suffering
> confusing log output like below:

Okay, it makes both code and log message easy to read.

Shevek, can you send the updated patch if you are agree with their
changes?

Thanks,

Kazutaka