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Posted to reviews@kudu.apache.org by "Todd Lipcon (Code Review)" <ge...@cloudera.org> on 2016/08/13 02:48:34 UTC

[kudu-CR] monotime: use a signed integer for the value 

Hello Mike Percy, Adar Dembo,

I'd like you to do a code review.  Please visit

    http://gerrit.cloudera.org:8080/3963

to review the following change.

Change subject: monotime: use a signed integer for the value
......................................................................

monotime: use a signed integer for the value

MonoTime previously used a uint64_t to store its value. This caused
problems in code patterns like:

  MonoTime gc_point = now;
  now.AddDelta(MonoTime::FromSeconds(-3600));
  if (gc_point.ComesBefore(some_other_time)) {
     ...
  }

In particular, the subtraction from 'gc_point' caused the unsigned
integer to wrap around such that _no_ time came before it.

One solution would have been to avoid the above pattern and only allow
adding positive deltas to a MonoTime. But, an easier one is to just use
a signed integer for the internal representation.

Change-Id: I68ce7b73a9a67becf91863161f0ae769153fe438
---
M src/kudu/util/monotime.h
1 file changed, 1 insertion(+), 1 deletion(-)


  git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/63/3963/1
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Gerrit-MessageType: newchange
Gerrit-Change-Id: I68ce7b73a9a67becf91863161f0ae769153fe438
Gerrit-PatchSet: 1
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: Mike Percy <mp...@apache.org>

[kudu-CR] monotime: use a signed integer for the value

Posted by "Todd Lipcon (Code Review)" <ge...@cloudera.org>.
Todd Lipcon has submitted this change and it was merged.

Change subject: monotime: use a signed integer for the value
......................................................................


monotime: use a signed integer for the value

MonoTime previously used a uint64_t to store its value. This caused
problems in code patterns like:

  MonoTime gc_point = now;
  now.AddDelta(MonoTime::FromSeconds(-3600));
  if (gc_point.ComesBefore(some_other_time)) {
     ...
  }

In particular, the subtraction from 'gc_point' caused the unsigned
integer to wrap around such that _no_ time came before it.

One solution would have been to avoid the above pattern and only allow
adding positive deltas to a MonoTime. But, an easier one is to just use
a signed integer for the internal representation.

Change-Id: I68ce7b73a9a67becf91863161f0ae769153fe438
Reviewed-on: http://gerrit.cloudera.org:8080/3963
Tested-by: Kudu Jenkins
Reviewed-by: Mike Percy <mp...@apache.org>
---
M src/kudu/util/monotime.h
1 file changed, 1 insertion(+), 1 deletion(-)

Approvals:
  Mike Percy: Looks good to me, approved
  Kudu Jenkins: Verified



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To view, visit http://gerrit.cloudera.org:8080/3963
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Gerrit-MessageType: merged
Gerrit-Change-Id: I68ce7b73a9a67becf91863161f0ae769153fe438
Gerrit-PatchSet: 2
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Mike Percy <mp...@apache.org>
Gerrit-Reviewer: Todd Lipcon <to...@apache.org>

[kudu-CR] monotime: use a signed integer for the value

Posted by "Mike Percy (Code Review)" <ge...@cloudera.org>.
Mike Percy has posted comments on this change.

Change subject: monotime: use a signed integer for the value
......................................................................


Patch Set 1: Code-Review+2

lgtm, assuming you did the napkin math and we have plenty of bits to go around

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Gerrit-MessageType: comment
Gerrit-Change-Id: I68ce7b73a9a67becf91863161f0ae769153fe438
Gerrit-PatchSet: 1
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Mike Percy <mp...@apache.org>
Gerrit-HasComments: No

[kudu-CR] monotime: use a signed integer for the value

Posted by "Todd Lipcon (Code Review)" <ge...@cloudera.org>.
Todd Lipcon has posted comments on this change.

Change subject: monotime: use a signed integer for the value
......................................................................


Patch Set 1:

yea, 2^63 microseconds is 292,277.266 years, so I dont think we're in danger of a system's uptime crossing that.

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Gerrit-MessageType: comment
Gerrit-Change-Id: I68ce7b73a9a67becf91863161f0ae769153fe438
Gerrit-PatchSet: 1
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Mike Percy <mp...@apache.org>
Gerrit-Reviewer: Todd Lipcon <to...@apache.org>
Gerrit-HasComments: No

[kudu-CR] monotime: use a signed integer for the value

Posted by "Kudu Jenkins (Code Review)" <ge...@cloudera.org>.
Kudu Jenkins has posted comments on this change.

Change subject: monotime: use a signed integer for the value
......................................................................


Patch Set 1:

Build Started http://104.196.14.100/job/kudu-gerrit/2856/

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Gerrit-MessageType: comment
Gerrit-Change-Id: I68ce7b73a9a67becf91863161f0ae769153fe438
Gerrit-PatchSet: 1
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Todd Lipcon <to...@apache.org>
Gerrit-Reviewer: Adar Dembo <ad...@cloudera.com>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Mike Percy <mp...@apache.org>
Gerrit-HasComments: No