Hi Adrian,
Thank you for the work =). Please see inline some comments.
Cheers,
Pedro
On 24-09-2012 09:35, Adrian Nistor wrote:
Hi Paolo,
the pending transactions were indeed a problem but this was solved by
issues ISPN-2306 [1] and ISPN-2312 [2].
Regarding point 1.5, this was implemented in
StateConsumerImpl.applyTransactions(..) and
StatePorviderImpl.getTransactionsForSegments(..). There was indeed a
missing piece that was corrected by ISPN-2306 (the lookedupEntries
field was not populated for transferred transactions, this is solved
by re-executing prepare on the new node).
ISPN-2312 also solves an issue with acquiring locks by these
transferred transactions, now we should be ok.
Regarding point 1.7, if the data is not available yet on a new owner
the write skew check will not detect any issue on this node indeed but
the check will fail on the other owners and cause a rollback on all
nodes anyway, so we should be safe here.
I'm not sure if this works fine when the number of owners is equals to
1. Isn't it possible a node send the prepapre right after the
Rebalance_Start to the joiner (the new owner)? If the joiner does not
have the data, it cannot perform a true write skew check. Am I missing
something?
Is the NBST alternative you mentioned applicable to TO only? We are
very interested to hear about you plans even if they are in an early
stage.
About the NBST for the TO, I have to block transactions that are writing
in keys of incoming segments. I didn't find any work around for this issue.
Thanks,
Adrian
[1] ISPN-2306 Remove the code that resends PrepareCommands
[https://issues.jboss.org/browse/ISPN-2306]
[2] ISPN-2312 TransactionTable does not compute minViewId correctly
after NBST was introduced [https://issues.jboss.org/browse/ISPN-2312]
On 09/14/20 12 07:51 PM, Paolo Romano wrote:
Hi all,
with Pedro we have been reasoning on the integration of TO-based
replication protocols, and a few questions popped out.
We may be missing something here, but it seems that the current NBST
implementation is still not providing support for pending
transactions, namely transactions that are prepared but not yet
committed at the time in which the node receives a state transfer
request. We have tried to figure out how you plan to do this by
checking the design document:
https://community.jboss.org/wiki/Non-BlockingStateTransferV2
but we still have some doubts. The relevant extract seems to be the
following:
1.3 For new segments, it asks one of the current owners (the
donor) for the transactions and locks.
1.4 The donor only replies with the transactions and locks after
it has installed the new toplogy. We need this to make sure a proper
pending CH is also installed on the donor and request forwarding to
the new pending owners is in place (forwarding is explained in
request handling section).
1.5 The transactions and locks are applied on acceptor.
1.6 The acceptor requests new data segments from donor
asynchronously.
1.7 Unblock all incoming commands. We are now prepared to
process commands although some data segments are still flowing in.
In point 1.7, you say that you can already process commands for data
segments that a node has not received yet. However, if the command
is, say, a prepare for a key in a missing data segment and the
transaction is requesting a validation (write-skew check), you would
still need to block as you need the most updated data version to
validate it. Are we getting it right?
Also, it seems that point 1.5 has not been coded yet. We are asking
this, as these functionalities are likely to be useful also for the
NBST version used by TO-based replication protocols. Thus, it'd
probably be better to wait for these parts to be stable and re-use
them, instead than implementing them from scratch and end-up possibly
with conflicting/incompatible implementations. When do you plan to
have this functionality implemented?
Finally, I wanted to point out that Roberto and Sebastiano have been
thinking about an alternative version of the NBST, which should
further reduce the blocking time of transactions. They're currently
still at the design stage, and are working to prepare a document that
we would like to share with you to get feedback/comments etc. We plan
to have a draft of the algorithm by Sept. 20.
Cheers,
Paolo
PS: I'll be travelling starting tomorrow and during next week, so I
may not be responding to emails very quickly.
On 7/25/12 12:16 PM, Dan Berindei wrote:
Sounds good to me, we should have a little more breathing room after
the NBST alpha to look at the state transfer integration.
Cheers
Dan
On Tue, Jul 24, 2012 at 6:08 PM, Mircea Markus
<mircea.mar...@jboss.com <mailto:mircea.mar...@jboss.com>> wrote:
Hi guys,
I've just had a chat with the CloudTM team(CC) around the
integration of TOB/TOA[1] into Infinispan. Here are some points:
- the TOB and TOA code has been reviewed in detail by us. The
only part missing is the state transfer integration
- there's not a lot of sense in integrating TOB/TOM over the
existing state transfer as we would not back port that to 5.1
and it would be dropped in 5.2
- CloudTM would rebase the TOB/TOA work on top of the alpha
NBST[2](ATM planned at the end of next week/3 Aug) and we'll
integrate that
- first releases of the TOB/TOA would be marked as experimental
in 5.2
How does that sound?
Cheers,
Mircea
[1] TOA used to be referred to as TOM (M from multicast). In
JGroups terminology that's an Anycast, so we decided to be
consistent with that and use TOAnycast.
[2] https://community.jboss.org/wiki/Non-blockingStateTransfer
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