Re: [infinispan-dev] An observation about total order and consistency
Hi Mircea,
if I recall correctly currently (with 2PC) the commit is sent
asynchronously (without waiting to gather acks). If this is correct,
then the transaction originator can return from a commit on a
transaction T before other nodes have actually applied T's updates.
Therefore, the second assert:
assert cache(1).get(k).equals(v); //might fail!
may fail as well using 2PC. Or am I missing something?
Cheers,
Paolo
On 3/7/12 1:44 AM, Mircea Markus wrote:
With total order and sync replication it is possible for the
following:
tm.begin()
cache(0).put(k,v);
tm.commit();
assert cache(0).get(k).equals(v); //always passes
assert cache(1).get(k).equals(v); //might fail!
//..but
eventually(cache(1).get(k).equals(v)) //this will always pass
In other words, after a transaction is completed, you are only guaranteed to see its
results on the originator node. On replicas the value is only eventually made available.
Whilst this is fine for embedded caches, as in practice the replication would happen
between different JVMs, this is still relevant for:
- hotrod: a client might tx-write on a node and read from the other
- tests
Cheers
Mircea
--
Mircea Markus
twitter.com/mirceamarkus
Sr. Software Engineer, Infinispan
http://www.infinispan.org
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