The namespace usage in this directory is very inconsistent, with files
and classes scattered in:
* global namespace
* namespace compaction
* namespace sstables
With cases, where all three used in the same file. This code used to
live in sstables/ and some of it still retains namespace sstables as a
heritage of that time. The mismatch between the dir (future module) and
the namespace used is confusing, so finish the migration and move all
code in compaction/ to namespace compaction too.
This patch, although large, is mechanic and only the following kind of
changes are made:
* replace namespace sstable {} with namespace compaction {}
* add namespace compaction {}
* drop/add sstables::
* drop/add compaction::
* move around forward-declarations so they are in the correct namespace
context
This refactoring revealed some awkward leftover coupling between
sstables and compaction, in sstables/sstable_set.cc, where the
make_sstable_set() methods of compaction strategies are implemented.
This will allow upcoming work to gently produce a sstable set for
each compaction group view. Example: repaired and unrepaired.
Locking strategy for compaction's sstable selection:
Since sstable retrieval path became futurized, tasks in compaction
manager will now hold the write lock (compaction_state::lock)
when retrieving the sstable list, feeding them into compaction
strategy, and finally registering selected sstables as compacting.
The last step prevents another concurrent task from picking the
same sstable. Previously, all those steps were atomic, but
we have seen stall in that area in large installations, so
futurization of that area would come sooner or later.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Since table_state is a view to a compaction group, it makes sense
to rename it as so.
With upcoming incremental repair, each replica::compaction_group
will be actually two compaction groups, so there will be two
views for each replica::compaction_group.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Add documentation to clarify the purpose and behavior of
make_interpose_consumer() in the compaction_strategy_impl class. This
method is crucial for building layered processing pipelines but its
semantics were previously undocumented.
The added documentation explains how:
- It decorates end consumers with additional processing steps
- It enables construction of processing pipelines
- The original consumer's semantics are preserved
This improves code maintainability by making the pipeline construction
pattern more apparent to developers.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#21336
This change adds the missing Cassandra compaction option unchecked_tombstone_compaction.
Setting this option to true causes the compaction to ignore tombstone_threshold,
and decide whether to do a compaction only on the value of tombstone_compaction_interval
When off-strategy is disabled, data segregation is not postponed,
meaning that getting partition estimate right is important to
decrease filter's false positives. With streaming, we don't
have min and max timestamps at destination, well, we could have
extended the RPC verb to send them, but turns out we can deduce
easily the amount of windows using default TTL. Given partitioner
random nature, it's not absurd to assume that a given range being
streamed may overlap with all windows, meaning that each range
will yield one sstable for each window when segregating incoming
data. Today, we assume the worst of 100 windows (which is the
max amount of sstables the input data can be segregated into)
due to the lack of metadata for estimating the window count.
But given that users are recommended to target a max of ~20
windows, it means partition estimate is being downsized 5x more
than needed. Let's improve it by using default TTL when
estimating window count, so even on absence of timestamp
metadata, the partition estimation won't be way off.
Fixes#15704.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
After "repair: Get rid of the gc_grace_seconds", the sstable's schema (mode,
gc period if applicable, etc) is used to estimate the amount of droppable
data (or determine full expiration = max_deletion_time < gc_before).
It could happen that the user switched from timeout to repair mode, but
sstables will still use the old mode, despite the user asked for a new one.
Another example is when you play with value of grace period, to prevent
data resurrection if repair won't be able to run in a timely manner.
The problem persists until all sstables using old GC settings are recompacted
or node is restarted.
To fix this, we have to feed latest schema into sstable procedures used
for expiration purposes.
Fixes#15643.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#15746
Now everything is prepared for the switch, let's do it.
Now let's wait for ICS to enjoy the set of changes.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Split compaction_strategy_impl constructor into methods that will
be reused for validation.
Add additional checks providing that options' values are legal.
Add compaction_strategy_impl::validate_min_max_threshold method
that will be used to validate min and max threshold values
for different compaction methods.
In that level no io_priority_class-es exist. Instead, all the IO happens
in the context of current sched-group. File API no longer accepts prio
class argument (and makes io_intent arg mandatory to impls).
So the change consists of
- removing all usage of io_priority_class
- patching file_impl's inheritants to updated API
- priority manager goes away altogether
- IO bandwidth update is performed on respective sched group
- tune-up scylla-gdb.py io_queues command
The first change is huge and was made semi-autimatically by:
- grep io_priority_class | default_priority_class
- remove all calls, found methods' args and class' fields
Patching file_impl-s is smaller, but also mechanical:
- replace io_priority_class& argument with io_intent* one
- pass intent to lower file (if applicatble)
Dropping the priority manager is:
- git-rm .cc and .hh
- sed out all the #include-s
- fix configure.py and cmakefile
The scylla-gdb.py update is a bit hairry -- it needs to use task queues
list for IO classes names and shares, but to detect it should it checks
for the "commitlog" group is present.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Closes#13963
So it can be used in the next patch that will refactor
compaction_state out of class compaction_manager.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
once compaction_strategy is made staless, the state must be retrieved
in notify_completion() through table_state.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Today, compaction_backlog_tracker is managed in each compaction_strategy
implementation. So every compaction strategy is managing its own
tracker and providing a reference to it through get_backlog_tracker().
But this prevents each group from having its own tracker, because
there's only a single compaction_strategy instance per table.
To remove this limitation, compaction_strategy impl will no longer
manage trackers but will instead provide an interface for trackers
to be created, such that each compaction group will be allowed to
have its own tracker, which will be managed by compaction manager.
On compaction strategy change, table will update each group with
the new tracker, which is created using the previously introduced
ompaction_group_sstable_set_updater.
Now table's backlog will be the sum of all compaction_group backlogs.
The normalization factor is applied on the sum, so we don't have
to adjust each individual backlog to any factor.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Pass the tombstone_gc_state from the compaction_strategy
to sstables get_gc_before_* functions using the table state
to get to the tombstone_gc_state.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
We should separate the scheduling groups used for major compaction
from the the regular compaction scheduling group so that
the latter can be affected by the backlog tracker in case
backlog accumulates during a long running major compaction.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Then caller can decide whether to copy or move candidate set into the
function. cleanup_sstables_compaction_task can move candidates as
it's no longer needed once it retrieves all descriptors.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Today, all compaction strategies will clean up their files using the
incremental approach of one sstable being rewritten at a time.
Turns out that's not the best approach performance wise. Let's take
STCS for example. As cleanup finishes rewriting one file, the output
file is placed into the sstable set. Regular now can compact that
file with another that was already there (e.g. produced by flush after
cleanup started). Inefficient compactions like this can keep happening
as cleanup incrementally places output file into the candidate list
for regular.
This method will allow strategies to clean up their files in batches.
For example, STCS can clean up all files in smallest tiers in single
round, allowing the output data to be added at once. So next compaction
rounds can be more efficient in terms of writeamp. Another benefit is
that deduplication and GC can happen more efficiently.
The drawback is the space requirement, as we no longer compact one file
a a time. However, the impact is minimized by cleaning up the smallest
tier first. With leveled strategy for example, even though 90% of data
is in highest level, the space requirement is not a problem because
we can apply the incremental compaction on its behalf. The same applies
to ICS. With STCS, the requirement is the size of the tier being
compacted, but that's already expected by its users anyway.
By the time being, all strategies have it unimplemented. so they still
use the old behavior where files are rewritten on at a time.
This will allow us to incrementally implement the cleanup method for
all compaction strategies.
Refs #10097.
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
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]
This strategy method was introduced unnecessarily. We assume it was
going to be needed, but turns out it was never needed, not even
for ICS. Also it's built on a wrong assumption as an output
sstable run being generated can never be compacted in parallel
as the non-overlapping requirement can be easily broken.
LCS for example can allow parallel compaction on different runs
(levels) but correctness cannto be guaranteed with same runs
are compacted in parallel.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Last method in compaction_strategy using table. From now on,
compaction strategy no longer works directly with table.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
From now on, get_major_compaction_job() will use table_state instead of
a plain reference to table.
Signed-off-by: Raphael S. Carvalho <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>
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>
