Re: [infinispan-dev] ISPN-263 and handling partitions
On 4/19/13 11:04 AM, Pedro Ruivo wrote:
I have another suggestion that can allow all the partitions to
process write commands.
I think we can rely on the primary owners to decide which partition
has the write permission on a key. For example, if the primary owner
of key1 is on partition_1, then the partition_1 has the only
partition that can update key1. All the remaining partitions only
have read access over key1.
This is problematic, as it doesn't take primary / minority partitions
into account. E.g if we have {A,B,C,D,E,F,G} and key1 is present on A
(primary owner) and G (backup owner), and the cluster splits into
{A,B,C,D} and {E,F,G}, then key1 might be on A (primary) and D (new
backup), but also on E (new primary) and G (old backup). Both partitions
would allow modifications to key1.
Also, if key1 was not present in the {E,F,G} partition, and some client
created it, nothing would prevent that, as we don't know the the other
partition's existence.
The problem with this approach is that we have to keep the
consistent hash before the partition occurs.
Yes, the issue is that you can *never* determine if a partition
occurred, or if some member(s) crashed, so in the above case a hard and
fast rule of the primary partition have at 4 or more members make sense
for a primary partition approach.
--
Bela Ban, JGroups lead (http://www.jgroups.org)