Hello Kudu Jenkins,
I'd like you to reexamine a change. Please visit
http://gerrit.cloudera.org:8080/4363
to look at the new patch set (#16).
Change subject: KUDU-1601. Delete ancient UNDO delta blocks in the background
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KUDU-1601. Delete ancient UNDO delta blocks in the background
This patch adds a maintenance manager background task that deletes
"ancient" UNDO delta blocks, which means blocks that correspond to data
that is considered no longer reachable and a candidate for garbage
collection. The task only deletes entire blocks and so does not provoke
write amplification.
This maintenance task operates in the following way:
1. UpdateStats() for the op returns the maximum potentially gc'able
bytes of undos in the rowset, which is the sum of all undo delta
store sizes up until an initialized one with
max_timestamp > the AHM (ancient history mark).
2. Perform() for the op initializes deltas for some budgeted amount of
time on the tablet. Per rowset it performs a binary search and
initializes undo delta stores until it finds the earliest one with
max_timestamp > AHM. That makes the next UpdateStats() call more
accurate. Then it starts from the oldest and initializes undos within
the budget. Finally, once it's through with its time budget, it
garbage-collects as many undos in the rowset as possible.
To avoid starvation of performance ops, there is a flag that
incorporates some randomness into the scheduler, at the MM level. This
limits the fraction of the time we consider data GC ops higher
priority than performance ops.
This patch includes the following:
* New UNDO delta block GC MM task
* New UNDO delta block GC metrics (at the tablet level only)
* Flags to enable / disable the GC task as well as flags to throttle it
* A few minor improvements in the maintenance manager
* Fixes for a few preexisting clang-tidy lint complaints
Notable implementation details:
* When performing undo delta GC in Tablet::DeleteAncientUndoDeltas(), we
only flush the tablet metadata after making the metadata changes
across all rowsets. This should be safe because we are not actually
modifying any data, we are simply removing references to blocks that
are no longer reachable by new scanners.
Includes the following tests:
* RowSet-level unit test in diskrowset-test
* Tablet-level functional test in tablet_history_gc-test
* Tablet-level concurrency test in mt-tablet-test
* Integration test utilizing the tserver-level MM task in
tablet_history_gc-itest
* Incorporated into RandomizedTabletHistoryGcITest in
tablet_history_gc-itest
Change-Id: I0309bf7acfb6d018860c80f354012c3500da5c68
---
M src/kudu/integration-tests/tablet_history_gc-itest.cc
M src/kudu/master/master.cc
M src/kudu/tablet/delta_tracker.cc
M src/kudu/tablet/delta_tracker.h
M src/kudu/tablet/diskrowset-test.cc
M src/kudu/tablet/diskrowset.cc
M src/kudu/tablet/diskrowset.h
M src/kudu/tablet/memrowset.h
M src/kudu/tablet/mock-rowsets.h
M src/kudu/tablet/mt-tablet-test.cc
M src/kudu/tablet/rowset.h
M src/kudu/tablet/rowset_metadata.cc
M src/kudu/tablet/rowset_metadata.h
M src/kudu/tablet/tablet.cc
M src/kudu/tablet/tablet.h
M src/kudu/tablet/tablet_history_gc-test.cc
M src/kudu/tablet/tablet_metrics.cc
M src/kudu/tablet/tablet_metrics.h
M src/kudu/tablet/tablet_mm_ops.cc
M src/kudu/tablet/tablet_mm_ops.h
M src/kudu/tserver/tablet_server.cc
M src/kudu/util/maintenance_manager-test.cc
M src/kudu/util/maintenance_manager.cc
M src/kudu/util/maintenance_manager.h
24 files changed, 1,256 insertions(+), 126 deletions(-)
git pull ssh://gerrit.cloudera.org:29418/kudu refs/changes/63/4363/16
--
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Gerrit-MessageType: newpatchset
Gerrit-Change-Id: I0309bf7acfb6d018860c80f354012c3500da5c68
Gerrit-PatchSet: 16
Gerrit-Project: kudu
Gerrit-Branch: master
Gerrit-Owner: Mike Percy <[email protected]>
Gerrit-Reviewer: Adar Dembo <[email protected]>
Gerrit-Reviewer: David Ribeiro Alves <[email protected]>
Gerrit-Reviewer: Jean-Daniel Cryans <[email protected]>
Gerrit-Reviewer: Kudu Jenkins
Gerrit-Reviewer: Mike Percy <[email protected]>
Gerrit-Reviewer: Tidy Bot
