_estimated_remaining_tasks gets updated via get_next_non_expired_sstables ->
get_compaction_candidates, but otherwise if we return earlier from
get_sstables_for_compaction, it does not get updated and may go out of sync.
Refs #10418
(to be closed when the fix reaches branch-4.6)
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Closes#10419
This continues the work in a69d98c3d0,
by implementing the cleanup method in TWCS to make it bucket aware.
Till now, the default impl was used which cleanups on file at a
time, starting from the smallest.
The cleanup strategy for TWCS is simple. It's simply calling the
size tiered cleanup method for each bucket, so there will be
one job for each tier in each window.
The next strategies to receive this improvement are LCS and ICS
(the latter one being only available in enterprise).
Refs #10097.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
For compaction to be able to purge expired data, like tombstones, a
sstable set snapshot is set in the compaction descriptor.
That's a decision that belongs to task type. For example, all regular
compaction enable GC, whereas scrub for example doesn't for safety
reasons.
The problem is that the decision is being made by every instantiation
of compaction_descriptor in the strategies, which is both unnecessary
and also adds lots of boilerplate to the code, making it hard to
understand and work with.
As sstable set snapshot is an implementation detail, a new method
is being added to compaction_descriptor to make the intention
clearer, making the interface easier to understand.
can_purge_tombstones, used previously by rewrite task only, is being
reused for communicating GC intention into task::compact_sstables().
The boilerplate was a pain when adding a new strategy method for
the ongoing work on cleanup, described by issue #10097.
Another benefit is that we'll now only create a set snapshot when
compaction will really run. Before, it could happen that the snapshot
would be discarded if the compaction attempt had to be postponed,
which is a waste of cpu cycles.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Instead of lengthy blurbs, switch to single-line, machine-readable
standardized (https://spdx.dev) license identifiers. The Linux kernel
switched long ago, so there is strong precedent.
Three cases are handled: AGPL-only, Apache-only, and dual licensed.
For the latter case, I chose (AGPL-3.0-or-later and Apache-2.0),
reasoning that our changes are extensive enough to apply our license.
The changes we applied mechanically with a script, except to
licenses/README.md.
Closes#9937
Currently, when TWCS reshape finds a bucket containing more than 32
files, it will blindly resize that bucket to 32.
That's very bad because it doesn't take into consideration that
compaction efficiency depends on relative sizes of files being
compacted together, meaning that a huge file can be compacted with
a tiny one, producing lots of write amplification.
To solve this problem, STCS reshape logic will now be reused in
each time bucket. So only similar-sized files are compacted together
and the time bucket will be considered reshaped once its size tiers
are properly compacted, according to the reshape mode.
Fixes#9938.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20220117205000.121614-1-raphaelsc@scylladb.com>
The gc_grace_seconds is a very fragile and broken design inherited from
Cassandra. Deleted data can be resurrected if cluster wide repair is not
performed within gc_grace_seconds. This design pushes the job of making
the database consistency to the user. In practice, it is very hard to
guarantee repair is performed within gc_grace_seconds all the time. For
example, repair workload has the lowest priority in the system which can
be slowed down by the higher priority workload, so that there is no
guarantee when a repair can finish. A gc_grace_seconds value that is
used to work might not work after data volume grows in a cluster. Users
might want to avoid running repair during a specific period where
latency is the top priority for their business.
To solve this problem, an automatic mechanism to protect data
resurrection is proposed and implemented. The main idea is to remove the
tombstone only after the range that covers the tombstone is repaired.
In this patch, a new table option tombstone_gc is added. The option is
used to configure tombstone gc mode. For example:
1) GC a tombstone after gc_grace_seconds
cqlsh> ALTER TABLE ks.cf WITH tombstone_gc = {'mode':'timeout'} ;
This is the default mode. If no tombstone_gc option is specified by the
user. The old gc_grace_seconds based gc will be used.
2) Never GC a tombstone
cqlsh> ALTER TABLE ks.cf WITH tombstone_gc = {'mode':'disabled'};
3) GC a tombstone immediately
cqlsh> ALTER TABLE ks.cf WITH tombstone_gc = {'mode':'immediate'};
4) GC a tombstone after repair
cqlsh> ALTER TABLE ks.cf WITH tombstone_gc = {'mode':'repair'};
In addition to the 'mode' option, another option 'propagation_delay_in_seconds'
is added. It defines the max time a write could possibly delay before it
eventually arrives at a node.
A new gossip feature TOMBSTONE_GC_OPTIONS is added. The new tombstone_gc
option can only be used after the whole cluster supports the new
feature. A mixed cluster works with no problem.
Tests: compaction_test.py, ninja test
Fixes#3560
[avi: resolve conflicts vs data_dictionary]
Once current window is sealed, TWCS is supposed to compact all its
sstables into one. If there's ongoing compaction, it can happen that
sstables are missed and therefore past windows will contain more than
one sstable. Additionally, it could happen that major doesn't happen
at all if under heavy load. All these problems are fixed by serializing
major on past window and also postponing it if manager refuses to run
the job now.
Fixes#9553.
Reviewed-by: Benny Halevy <bhalevy@scylladb.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
STCS option can be retrieved from class member, as newest_bucket()
is no longer a static function. let's get rid of it.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
When reshaping TWCS table in relaxed mode, which is the case for
offstrategy and boot, disjoint tolerance is too strict, which can
lead those processes to do more work than needed.
Let's increase the tolerance to max threshold, which will limit the
amount of sstables opened in compaction to a reasonable amount.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20211130132538.56285-1-raphaelsc@scylladb.com>
From now on, get_sstables_for_compaction() will use table_state.
With table_state, we avoid layer violations like strategy using
manager and also makes testing easier.
Compaction unit tests were temporarily disabled to avoid a giant
commit which is hard to parse.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
It's much more efficient to have a separate compaction task that consists
completely from expired sstables and make sure it gets a unique "weight" than
mixing expired sstables with non-expired sstables adding an unpredictable
latency to an eviction event of an expired sstable.
This change also improves the visibility of eviction events because now
they are always going to appear in the log as compactions that compact into
an empty set.
Fixes#9533
Signed-off-by: Vlad Zolotarov <vladz@scylladb.com>
Closes#9534
With 062436829c,
we return all input sstables in strict mode
if they are dosjoint even if they don't need reshaping at all.
This leads to an infinite reshape loop when uploading sstables
with TWCS.
The optimization for disjoint sstables is worth it
also in relaxed mode, so this change first makes sorting of the input
sstables by first_key order independent of reshape_mode,
and then it add a check for sstable_set_overlapping_count
before trimming either the multi_window vector or
any single_window bucket such that we don't trim the list
if the candidates are disjoint.
Adjust twcs_reshape_with_disjoint_set_test accordingly.
And also add some debug logging in
time_window_compaction_strategy::get_reshaping_job
so one can figure out what's going on there.
Test: unit(dev)
DTest: cdc_snapshot_operation.py:CDCSnapshotOperationTest.test_create_snapshot_with_collection_list_with_base_rows_delete_type
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Message-Id: <20211025071828.509082-1-bhalevy@scylladb.com>
TWCS can reshape at most 32 sstables spanning multiple windows, in a
single compaction round. Which sstables are compacted together, when
there are more than 32 sstables, is random.
If sstables with overlapping windows are compacted together, then
write amplification can be reduced because we may be able to push
all the data to a window W in a single compaction round, so we'll
not have to perform another compaction round later in W, to reduce
its number of files. This is also very good to reduce the amount
of transient file descriptors opened, because TWCS reshape
first reshapes all sstables spanning multiple windows, so if
all windows temporarily grow large in number of files, then
there's a risk which file descriptors can be exhausted.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Reviewed-by: Benny Halevy <bhalevy@scylladb.com>
Message-Id: <20211013203046.233540-3-raphaelsc@scylladb.com>
After a4053dbb72, data segregation is postponed to offstrategy, so reshape
procedure is called with disjoint sstables which belong to different
windows, so let's extend the optimization for disjoint sstables which
span more than one window. In this way, write amplification is reduced
for offstrategy compaction, as all disjoint sstables will be compacted
at once.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20211013203046.233540-2-raphaelsc@scylladb.com>
the name compaction_options is confusing as it overlaps in meaning
with compaction_descriptor. hard to reason what are the exact
difference between them, without digging into the implementation.
compaction_options is intended to only carry options specific to
a give compaction type, like a mode for scrub, so let's rename
it to compaction_type_options to make it clearer for the
readers.
[avi: adjust for scrub changes]
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210908003934.152054-1-raphaelsc@scylladb.com>
Since compaction is layered on top of sstables, let's move all compaction code
into a new top-level directory.
This change will give me extra motivation to remove all layer violations, like
sstable calling compaction-specific code, and compaction entanglement with
other components like table and storage service.
Next steps:
- remove all layer violations
- move compaction code in sstables namespace into a new one for compaction.
- move compaction unit tests into its own file
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20210707194058.87060-1-raphaelsc@scylladb.com>
