Andrew,
Andrew Beekhof napsal(a):
On Thu, Jun 14, 2012 at 11:19 PM, Jan Friesse<jfriesse@xxxxxxxxxx> wrote:
Let's say we have 2 nodes:
- node 2 is paused
- node 1 create membership (one node)
- node 2 is unpaused
Result is that node 1 downlist is selected, so it means that
from node 2 point of view, node 1 was never down.
This behaviour makes sense to me.
Although ideally node2 wouldn't get a membership event until everyone
agreed whether it was a member or not*.
Is that feasible?
I'm unsure what do you mean. Everyone in this specific case is only node
1 and node 2. When node 2 was paused, node 1 had only chance to create
membership, and this was one node membership. When node 2 was unpaused,
we must "simulate" all events which happened in time of it's pause. This
was, creation of one node membership (only node 2). And after that, we
can process new membership (node 2 + node 1). So I can say that it's
true that everyone else (node 1) agreed that node 2 was not part of
membership and now it is.
Also keep in mind that this patch fixes behavior which is not happening
so often. Usually we have odd number of nodes AND more then 1, so 3, 5,
... and in such situation, this patch doesn't have any effect (because
of test #1).
But maybe I didn't understood requirement. If so, can you please
elaborate little more how do you think membership should look like?
* That or clients might need to be made more tolerant of being kicked
out of the membership list.
With 3 patches I've send, there shouldn't happen that node itself is
kicked from membership (with one exception - localhost rebind what I'm
working on to fix) by other nodes. It's always "other nodes left
membership" on that node and on other nodes it is "that node left
membership".
Regards,
Honza
Patch solves situation by adding additional check for largest
previous membership.
So current tests are:
1) largest (previous #nodes - #nodes know to have left)
2) (then) largest previous membership
3) (and last as a tie-breaker) node with smallest nodeid
Signed-off-by: Jan Friesse<jfriesse@xxxxxxxxxx>
---
services/cpg.c | 17 +++++++++--------
1 files changed, 9 insertions(+), 8 deletions(-)
diff --git a/services/cpg.c b/services/cpg.c
index 7e62260..533f0c9 100644
--- a/services/cpg.c
+++ b/services/cpg.c
@@ -816,16 +816,17 @@ static struct downlist_msg* downlist_master_choose (void)
best_members = best->old_members - best->left_nodes;
cmp_members = cmp->old_members - cmp->left_nodes;
- if (cmp_members< best_members) {
- continue;
- }
- else if (cmp_members> best_members) {
- best = cmp;
- }
- else if (cmp->sender_nodeid< best->sender_nodeid) {
+ if (cmp_members> best_members) {
best = cmp;
+ } else if (cmp_members == best_members) {
+ if (cmp->old_members> best->old_members) {
+ best = cmp;
+ } else if (cmp->old_members == best->old_members) {
+ if (cmp->sender_nodeid< best->sender_nodeid) {
+ best = cmp;
+ }
+ }
}
-
}
assert (best != NULL);
--
1.7.1
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