txnbuf: Add write count budget, size budget.

txnbuf: Add write count budget, size budget.

Add a "maximum number of datastore writes" budget to the transaction
buffer. Rework the size budget to remove preemptive child transaction
failures and directly derive budget from the parent.

BUG=

Committed: https://github.com/luci/gae/commit/1ad17ed9115aa1e9414475e6bd60da943705f02b

[dnj, 2016-03-09 00:57:44]

dnj@chromium.org changed reviewers:
+ iannucci@chromium.org

[dnj, 2016-03-09 00:57:45]

PTAL

[iannucci, 2016-03-09 01:02:55]

lgtm

[iannucci, 2016-03-09 01:03:06]

The CQ bit was checked by iannucci@chromium.org

[commit-bot: I haz the power, 2016-03-09 01:03:08]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1776833002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1776833002/1

[commit-bot: I haz the power, 2016-03-09 01:08:06]

Description was changed from

==========
txnbuf: Add write count budget, size budget.

Add a "maximum number of datastore writes" budget to the transaction
buffer. Rework the size budget to remove preemptive child transaction
failures and directly derive budget from the parent.

BUG=
==========

to

==========
txnbuf: Add write count budget, size budget.

Add a "maximum number of datastore writes" budget to the transaction
buffer. Rework the size budget to remove preemptive child transaction
failures and directly derive budget from the parent.

BUG=

Committed:
https://github.com/luci/gae/commit/1ad17ed9115aa1e9414475e6bd60da943705f02b
==========

[commit-bot: I haz the power, 2016-03-09 01:08:07]

Committed patchset #1 (id:1) as
https://github.com/luci/gae/commit/1ad17ed9115aa1e9414475e6bd60da943705f02b