LogDog: Add Storage-layer data caching.

LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

This switches over "endpoints" Get test to use a memory-backed BigTable
implementation instead of a pure memory intermediate storage instance.
This exercises more of the real production code paths during gets,
including the new caching path.

TBR=nodir@chromium.org
BUG=chromium:657016
TEST=None

Committed: https://github.com/luci/luci-go/commit/36e46653dea3598592b8913583273107c472b540

[dnj, 2016-10-20 18:40:19]

dnj@chromium.org changed reviewers:
+ nodir@chromium.org, vadimsh@chromium.org

[dnj, 2016-10-20 18:40:19]

PTAL. Just throwing this out b/c I have to run for the day, LMK if you have time
to review this and if you have any questions.

[dnj, 2016-10-26 18:22:22]

The CQ bit was checked by dnj@chromium.org

[commit-bot: I haz the power, 2016-10-26 18:22:31]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[dnj, 2016-10-26 18:22:31]

Description was changed from

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

BUG=chromium:657016
TEST=None
==========

to

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

TBR=nodir@chromium.org
BUG=chromium:657016
TEST=None
==========

[commit-bot: I haz the power, 2016-10-26 18:22:32]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-10-26 18:22:32]

No L-G-T-M from a valid reviewer yet. 
CQ run can only be started by full committers or once the patch has
received an L-G-T-M from a full committer.
Even if an L-G-T-M may have been provided, it was from a non-committer,
_not_ a full super star committer.
Committers are members of the group "project-infra-committers".
Note that this has nothing to do with OWNERS files.

[dnj, 2016-10-26 18:24:27]

The CQ bit was unchecked by dnj@chromium.org

[dnj, 2016-10-26 20:26:29]

Description was changed from

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

TBR=nodir@chromium.org
BUG=chromium:657016
TEST=None
==========

to

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

This switches over "endpoints" Get test to use a memory-backed BigTable
implementation instead of a pure memory intermediate storage instance.
This exercises more of the real production code paths during gets,
including the new caching path.

BUG=chromium:657016
TEST=None
==========

[dnj, 2016-10-26 21:46:14]

The CQ bit was checked by dnj@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-26 21:46:22]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-26 22:55:41]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-10-26 22:55:42]

Dry run: Try jobs failed on following builders:
  Luci-go Win Tester on luci.infra.try (JOB_FAILED,
https://luci-milo.appspot.com/swarming/task/321bc7125671df10)

[dnj, 2016-10-27 03:20:10]

The CQ bit was checked by dnj@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2016-10-27 03:20:13]

Dry run: CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-27 03:27:23]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2016-10-27 03:27:24]

Dry run: This issue passed the CQ dry run.

[dnj, 2016-10-27 03:30:13]

Description was changed from

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

This switches over "endpoints" Get test to use a memory-backed BigTable
implementation instead of a pure memory intermediate storage instance.
This exercises more of the real production code paths during gets,
including the new caching path.

BUG=chromium:657016
TEST=None
==========

to

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

This switches over "endpoints" Get test to use a memory-backed BigTable
implementation instead of a pure memory intermediate storage instance.
This exercises more of the real production code paths during gets,
including the new caching path.

TBR=nodir@chromium.org
BUG=chromium:657016
TEST=None
==========

[dnj, 2016-10-27 03:30:19]

The CQ bit was checked by dnj@chromium.org

[commit-bot: I haz the power, 2016-10-27 03:30:24]

CQ is trying da patch. Follow status at
 
https://chromium-cq-status.appspot.com/v2/patch-status/codereview.chromium.or...

[commit-bot: I haz the power, 2016-10-27 03:35:49]

Description was changed from

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

This switches over "endpoints" Get test to use a memory-backed BigTable
implementation instead of a pure memory intermediate storage instance.
This exercises more of the real production code paths during gets,
including the new caching path.

TBR=nodir@chromium.org
BUG=chromium:657016
TEST=None
==========

to

==========
LogDog: Add Storage-layer data caching.

This adds a generic Storage caching system and a memcache implementation
in the Coordinator application.

It also integrates that caching into two Storage subsystems:
- For BigTable-based Storage, the last "Tail" cursor is cached to
  speed up subsequent Tail operations.
- For Archive-based Storage, the log's index is cached to speed up
  subsequent log accesses.

This switches over "endpoints" Get test to use a memory-backed BigTable
implementation instead of a pure memory intermediate storage instance.
This exercises more of the real production code paths during gets,
including the new caching path.

TBR=nodir@chromium.org
BUG=chromium:657016
TEST=None

Committed:
https://github.com/luci/luci-go/commit/36e46653dea3598592b8913583273107c472b540
==========

[commit-bot: I haz the power, 2016-10-27 03:35:50]

Committed patchset #3 (id:40001) as
https://github.com/luci/luci-go/commit/36e46653dea3598592b8913583273107c472b540