[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[Todd Lipcon (Code Review)]

Todd Lipcon has submitted this change and it was merged. ( 
http://gerrit.cloudera.org:8080/8964 )

Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..

[mvcc] Fix watermark advancement in the absence of committed transactions

MvccSnapshot's 'none_committed_at_or_after_' (ncaoa) watermark
indicates the point after which no transactions are committed.
This is used to cull redo deltas that cannot contain any
committed transactions under a snapshot, thus reducing work when
applying deltas.

By definition, this watermark is never supposed to be lower than
the 'all_committed_before_' watermark. If this invariant is broken
delta selection might be wrong by skipping whole delta files.

Normally the ncaoa watermark is advanced when transactions are
marked as committed, in which case this is done correctly. However
there is problem when the 'all_committed_before_' watermark
is advanced and there are no committed or in flight transactions.
In this case the ncaoa watermark might be left behind, manifesting
as incorrect delta application/skipping or even crashes.

This patch includes a fix and a very directed test that makes sure
it is correct. A follow up patch includes a new test in fuzz-itest
that would trigger a crash without the fix.

Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Reviewed-on: http://gerrit.cloudera.org:8080/8964
Tested-by: David Ribeiro Alves 
Reviewed-by: Todd Lipcon 
---
M src/kudu/tablet/mvcc-test.cc
M src/kudu/tablet/mvcc.cc
M src/kudu/tablet/mvcc.h
3 files changed, 50 insertions(+), 1 deletion(-)

Approvals:
  David Ribeiro Alves: Verified
  Todd Lipcon: Looks good to me, approved

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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: merged
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 3
Gerrit-Owner: David Ribeiro Alves 
Gerrit-Reviewer: David Ribeiro Alves 
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Todd Lipcon 

[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[Todd Lipcon (Code Review)]

Todd Lipcon has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/8964 )

Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..


Patch Set 2: Code-Review+2


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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 2
Gerrit-Owner: David Ribeiro Alves 
Gerrit-Reviewer: David Ribeiro Alves 
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Todd Lipcon 
Gerrit-Comment-Date: Tue, 09 Jan 2018 20:14:01 +
Gerrit-HasComments: No

[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[David Ribeiro Alves (Code Review)]

David Ribeiro Alves has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/8964 )

Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..


Patch Set 2: Verified+1

Unrelated failure: "RaftConsensusITest.TestReplicaBehaviorViaRPC"


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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 2
Gerrit-Owner: David Ribeiro Alves 
Gerrit-Reviewer: David Ribeiro Alves 
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Todd Lipcon 
Gerrit-Comment-Date: Tue, 09 Jan 2018 08:32:59 +
Gerrit-HasComments: No

[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[David Ribeiro Alves (Code Review)]

David Ribeiro Alves has removed a vote on this change.

Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..


Removed Verified-1 by Kudu Jenkins (120)
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: deleteVote
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 2
Gerrit-Owner: David Ribeiro Alves 
Gerrit-Reviewer: David Ribeiro Alves 
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Todd Lipcon 

[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[David Ribeiro Alves (Code Review)]

David Ribeiro Alves has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/8964 )

Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..


Patch Set 1:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/8964/1//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/8964/1//COMMIT_MSG@9
PS1, Line 9: ncaof
> this abbreviation doesn't seem to match the first letters of those words :)
Done


http://gerrit.cloudera.org:8080/#/c/8964/1/src/kudu/tablet/mvcc-test.cc
File src/kudu/tablet/mvcc-test.cc:

http://gerrit.cloudera.org:8080/#/c/8964/1/src/kudu/tablet/mvcc-test.cc@745
PS1, Line 745: // In this case we'll advance safe/clean time but not the 
'none_committed_at_or_after_',
 : // meaning this watermark remains lower than safe/clean time.
 : /
> i'm confused by this comment for this test... are you describing the test's
right, my bad. fixed



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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 1
Gerrit-Owner: David Ribeiro Alves 
Gerrit-Reviewer: David Ribeiro Alves 
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Todd Lipcon 
Gerrit-Comment-Date: Tue, 09 Jan 2018 01:32:49 +
Gerrit-HasComments: Yes

[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[David Ribeiro Alves (Code Review)]

Hello Kudu Jenkins, Todd Lipcon,

I'd like you to reexamine a change. Please visit

http://gerrit.cloudera.org:8080/8964

to look at the new patch set (#2).

Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..

[mvcc] Fix watermark advancement in the absence of committed transactions

MvccSnapshot's 'none_committed_at_or_after_' (ncaoa) watermark
indicates the point after which no transactions are committed.
This is used to cull redo deltas that cannot contain any
committed transactions under a snapshot, thus reducing work when
applying deltas.

By definition, this watermark is never supposed to be lower than
the 'all_committed_before_' watermark. If this invariant is broken
delta selection might be wrong by skipping whole delta files.

Normally the ncaoa watermark is advanced when transactions are
marked as committed, in which case this is done correctly. However
there is problem when the 'all_committed_before_' watermark
is advanced and there are no committed or in flight transactions.
In this case the ncaoa watermark might be left behind, manifesting
as incorrect delta application/skipping or even crashes.

This patch includes a fix and a very directed test that makes sure
it is correct. A follow up patch includes a new test in fuzz-itest
that would trigger a crash without the fix.

Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
---
M src/kudu/tablet/mvcc-test.cc
M src/kudu/tablet/mvcc.cc
M src/kudu/tablet/mvcc.h
3 files changed, 50 insertions(+), 1 deletion(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/64/8964/2
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newpatchset
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 2
Gerrit-Owner: David Ribeiro Alves 
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Todd Lipcon 

[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[Todd Lipcon (Code Review)]

Todd Lipcon has posted comments on this change. ( 
http://gerrit.cloudera.org:8080/8964 )

Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..


Patch Set 1:

(2 comments)

http://gerrit.cloudera.org:8080/#/c/8964/1//COMMIT_MSG
Commit Message:

http://gerrit.cloudera.org:8080/#/c/8964/1//COMMIT_MSG@9
PS1, Line 9: ncaof
this abbreviation doesn't seem to match the first letters of those words :)


http://gerrit.cloudera.org:8080/#/c/8964/1/src/kudu/tablet/mvcc-test.cc
File src/kudu/tablet/mvcc-test.cc:

http://gerrit.cloudera.org:8080/#/c/8964/1/src/kudu/tablet/mvcc-test.cc@745
PS1, Line 745: // In this case we'll advance safe/clean time but not the 
'none_committed_at_or_after_',
 : // meaning this watermark remains lower than safe/clean time.
 : /
i'm confused by this comment for this test... are you describing the test's 
status when it was failing?



--
To view, visit http://gerrit.cloudera.org:8080/8964
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: comment
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 1
Gerrit-Owner: David Ribeiro Alves 
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Todd Lipcon 
Gerrit-Comment-Date: Tue, 09 Jan 2018 00:03:10 +
Gerrit-HasComments: Yes

[kudu-CR] [mvcc] Fix watermark advancement in the absence of committed transactions

[David Ribeiro Alves (Code Review)]

David Ribeiro Alves has uploaded this change for review. ( 
http://gerrit.cloudera.org:8080/8964


Change subject: [mvcc] Fix watermark advancement in the absence of committed 
transactions
..

[mvcc] Fix watermark advancement in the absence of committed transactions

MvccSnapshot's 'none_committed_at_or_after_' (ncaof) watermark
indicates the point after which no transactions are committed.
This is used to cull redo deltas that cannot contain any
committed transactions under a snapshot, thus reducing work when
applying deltas.

By definition, this watermark is never supposed to be lower than
the 'all_committed_before_' watermark. If this invariant is broken
delta selection might be wrong by skipping whole delta files.

Normally the ncaof watermark is advanced when transactions are
marked as committed, in which case this is done correctly. However
there is problem when the 'all_committed_before_' watermark
is advanced and there are no committed or in flight transactions.
In this case the ncaof watermark might be left behind, manifesting
as incorrect delta application/skipping or even crashes.

This patch includes a fix and a very directed test that makes sure
it is correct. A follow up patch includes a new test in fuzz-itest
that would trigger a crash without the fix.

Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
---
M src/kudu/tablet/mvcc-test.cc
M src/kudu/tablet/mvcc.cc
M src/kudu/tablet/mvcc.h
3 files changed, 48 insertions(+), 1 deletion(-)



  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/64/8964/1
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Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-MessageType: newchange
Gerrit-Change-Id: Icf94ea289204adf2eed797c3623cdea1b11b09db
Gerrit-Change-Number: 8964
Gerrit-PatchSet: 1
Gerrit-Owner: David Ribeiro Alves