Todd Lipcon has posted comments on this change.

Change subject: Simplify OpId/Timestamp assignment and make it atomic
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Patch Set 8:

(2 comments)

need to look in more detail at the changes in consensus/ but some quicker 
questions about the MvccManager design

http://gerrit.cloudera.org:8080/#/c/7221/8/src/kudu/tablet/transactions/transaction_driver.cc
File src/kudu/tablet/transactions/transaction_driver.cc:

Line 267:       prepare_state_ = PREPARED;
it's sketching me out that the state transition to PREPARED happens under this 
lock acquisition for followers but not until down below for leaders. Why can't 
we keep it as it was?


Separate note: I think the big block comment in the header needs to be tweaked 
a bit.


PS8, Line 295:       // Register a dummy transaction with mvcc manager that 
we'll abort later.
instead of using a dummy transaction, would it be possible to register it early 
with the current clock time, as you've done here, and add a new API like 
MvccManager::PushTransactionTimestamp(scoped_txn, new_timestamp) which changes 
the timestamp of the existing entry?

This would avoid an allocation at least and can include an assertion that you 
can only PushTransactionTimestamp to a later timestamp


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Gerrit-MessageType: comment
Gerrit-Change-Id: I2bedcc5c3708d06f48131f34ea14c835867b4800
Gerrit-PatchSet: 8
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: David Ribeiro Alves <[email protected]>
Gerrit-Reviewer: David Ribeiro Alves <[email protected]>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Tidy Bot
Gerrit-Reviewer: Todd Lipcon <[email protected]>
Gerrit-HasComments: Yes

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