Column names containing hyphens must be double-quoted. Also fix
the PRIMARY KEY reference from 'customer_id' (non-existent) to
'cust_id' (the actual column).
There are several reasons we want to do that.
One is that it will give us more flexibility in distributing the
load. We can subdivide tablets at any token, and achieve more
evenly-sized tablets. In particular, we can isolate large partitions
into separate tablets.
We can also split and merge incrementally individual tablets.
Currently, we do it for the whole table or nothing, which makes
splits and merges take longer and cause wide swings of the count.
This is not implemented in this PR yet, we still split/merge the whole table.
Another reason is vnode to tablets migration. We now could construct a
tablet map which matches exactly the vnode boundaries, so migration
can happen transparently from CQL-coordinator point of view.
Tablet count is still a power-of-two by default for newly created tables.
It may be different if tablet map is created by non-standard means,
or if per-table tablet option "pow2_count" is set to "false".
build/release/scylla perf-tablets:
Memory footprint for 131k tablets increased from 56 MiB to 58.1 MiB (+3.5%)
Before:
```
Generating tablet metadata
Total tablet count: 131072
Size of tablet_metadata in memory: 57456 KiB
Copied in 0.014346 [ms]
Cleared in 0.002698 [ms]
Saved in 1234.685303 [ms]
Read in 445.577881 [ms]
Read mutations in 299.596313 [ms] 128 mutations
Read required hosts in 247.482742 [ms]
Size of canonical mutations: 33.945053 [MiB]
Disk space used by system.tablets: 1.456761 [MiB]
Tablet metadata reload:
full 407.69ms
partial 2.65ms
```
After:
```
Generating tablet metadata
Total tablet count: 131072
Size of tablet_metadata in memory: 59504 KiB
Copied in 0.032475 [ms]
Cleared in 0.002965 [ms]
Saved in 1093.877441 [ms]
Read in 387.027100 [ms]
Read mutations in 255.752121 [ms] 128 mutations
Read required hosts in 211.202805 [ms]
Size of canonical mutations: 33.954453 [MiB]
Disk space used by system.tablets: 1.450162 [MiB]
Tablet metadata reload:
full 354.50ms
partial 2.19ms
```
Closesscylladb/scylladb#28459
* github.com:scylladb/scylladb:
test: boost: tablets: Add test for merge with arbitrary tablet count
tablets, database: Advertise 'arbitrary' layout in snapshot manifest
tablets: Introduce pow2_count per-table tablet option
tablets: Prepare for non-power-of-two tablet count
tablets: Implement merged tablet_map constructor on top of for_each_sibling_tablets()
tablets: Prepare resize_decision to hold data in decisions
tablets: table: Make storage_group handle arbitrary merge boundaries
tablets: Make stats update post-merge work with arbitrary merge boundaries
locator: tablets: Support arbitrary tablet boundaries
locator: tablets: Introduce tablet_map::get_split_token()
dht: Introduce get_uniform_tokens()
By default it's true, in which case tablet count of the table is
rounded up to a power of two. This option allows lifting this, in
which case the count can be arbitrary. This will allow testing the
logic of arbitrary tablet count.
RF change of tablet keyspace starts tablet rebuilds. Even if any of
the rebuilds is rolled back (because pending replica was excluded),
rf change request finishes successfully. Yet, we are left with not
enough replicas. Then, a next new rf change request handler would
generate a rebuild of two replicas of the same tablet. Such a transition
would not be applied, as we don't allow many pending replicas.
An exception would be thrown and the request would be retried infinitely,
blocking the topology coordinator.
Throw and fail rf change request if there is not enough replicas.
The request should be retried later, after the issue is fixed
by the mechanism introduced in previous changes.
Currently, repair-mode tombstone-gc cannot be used on tables with RF=1. We want to make repair-mode the default for all tablet tables (and more, see https://github.com/scylladb/scylladb/issues/22814), but currently a keyspace created with RF=1 and later altered to RF>1 will end up using timeout-mode tombstone gc. This is because the repair-mode tombstone-gc code relies on repair history to determine the gc-before time for keys/ranges. RF=1 tables cannot run repairs so they will have empty repair history and consequently won't be able to purge tombstones.
This PR solves this by keeping a registry of RF=1 tables and consulting this registry when creating `tombstone_gc_state` objects. If the table is RF=1, tombstone-gc will work as if the table used immediate-mode tombstone-gc. The registry is updated on each replication update. As soon as the table is not RF=1 anymore, the tombstone-gc reverts to the natural repair-mode behaviour.
After this PR, tombstone-gc defaults to repair-mode for all tables, regardless of RF and tablets/vnodes.
Fixes: SCYLLADB-106.
New feature, no backport required.
Closesscylladb/scylladb#22945
* github.com:scylladb/scylladb:
test/{boost,cluster}: add test for tombstone gc mode=repair with RF=1
tombstone_gc: allow use of repair-mode for RF=1 tables
replica/table: update rf=1 table registry in shared tombstone-gc state
tombstone_gc: tombstone_gc_before_getter: consider RF when getting gc before time
tombstone_gc: unpack per_table_history_maps
tombstone_gc: extract _group0_gc_time from per_table_history_map
tombstone_gc: drop tombstone_gc_state(nullptr) ctor and operator bool()
test/lib/random_schema: use timeout-mode tombstone_gc
tombstone_gc_options: add C++ friendly constructor
test: move away from tombstone_gc_state(nullptr) ctor
treewide: move away from tombstone_gc_state(nullptr) ctor
sstable: move away from tombstone_gc_mode::operator bool()
replica/table: add get_tombstone_gc_state()
compaction: use tombstone_gc_state with value semantics
db/row_cache: use tombstone_gc_state with value semantics
tombstone_gc: introduce tombstone_gc_state::for_tests()
Modify the methods which calculate the default gc mode as well as that
which validates whether repair-mode can be used at all, so both accepts
use of repair-mode on RF=1 tables.
This de-facto changes the default tombstone-gc to repair-mode for all
tables. Documentation is updated accordingly.
Some tests need adjusting:
* cqlpy/test_select_from_mutation_fragments.py: disable GC for some test
cases because this patch makes tombstones they write subject to GC
when using defaults.
* test/cluster/test_mv.py::test_mv_tombstone_gc_not_inherited used
repair-mode as a non-default for the base table and expected the MV to
revert to default. Another mode has to be used as the non-default
(immediate).
* test/cqlpy/test_tools.py::test_scylla_sstable_dump_schema: don't
compare tombstone_gc schema extension when comparing dumped schema vs.
original. The tool's schema loader doesn't have access to the keyspace
definition so it will come up with different defaults for
tombstone-gc.
* test/boost/row_cache_test.cc::test_populating_cache_with_expired_and_nonexpired_tombstones
sets tombstone expiry assuming the tombstone-gc timeout-mode default.
Change the CREATE TABLE statement to set the expected mode.
Introduced a new max_tablet_count tablet option that caps the maximum number of tablets a table can have. This feature is designed primarily for backup and restore workflows.
During backup, when load balancing is disabled for snapshot consistency, the current tablet count is recorded in the backup manifest.
During restore, max_tablet_count is set to this recorded value, ensuring the restored table's tablet count never exceeds the original snapshot's tablet distribution.
This guarantee enables efficient file-based SSTable streaming during restore, as each SSTable remains fully contained within a single tablet boundary.
Closesscylladb/scylladb#28450
Add user-facing documentation for the new CQL per-row TTL feature,
in docs/cql/cql-extensions.md.
Also mention (and link) the new alternative TTL feature in a few
relevant documents about the old (per-write) TTL, about CDC,
and about the CREATE TABLE and ALTER TABLE commands.
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
This parameter was not mentioned at all anywhere in the documentation.
Add an explanation of this parameter: why we need it, what is the
default and how it can be changed.
Closesscylladb/scylladb#28132
Mark rf_rack_valid_keyspaces option as deprecated. User should
use enforce_rack_list option instead.
The option can still be used and it does not change it's behavior.
Docs is updated accordingly.
Allow creating materialized views and secondary indexes in a tablets keyspace only if it's RF-rack-valid, and enforce RF-rack-validity while the keyspace has views by restricting some operations:
* Altering a keyspace's RF if it would make the keyspace RF-rack-invalid
* Adding a node in a new rack
* Removing / Decommissioning the last node in a rack
Previously the config option `rf_rack_valid_keyspaces` was required for creating views. We now remove this restriction - it's not needed because we always maintain RF-rack-validity for keyspaces with views.
The restrictions are relevant only for keyspaces with numerical RF. Keyspace with rack-list-based RF are always RF-rack-valid.
Fixesscylladb/scylladb#23345
Fixes https://github.com/scylladb/scylladb/issues/26820
backport to relevant versions for materialized views with tablets since it depends on rf-rack validity
Closesscylladb/scylladb#26354
* github.com:scylladb/scylladb:
docs: update RF-rack restrictions
cql3: don't apply RF-rack restrictions on vector indexes
cql3: add warning when creating mv/index with tablets about rf-rack
service/tablet_allocator: always allow tablet merge of tables with views
locator: extend rf-rack validation for rack lists
test: test rf-rack validity when creating keyspace during node ops
locator: fix rf-rack validation during node join/remove
test: test topology restrictions for views with tablets
test: add test_topology_ops_with_rf_rack_valid
topology coordinator: restrict node join/remove to preserve RF-rack validity
topology coordinator: add validation to node remove
locator: extend rf-rack validation functions
view: change validate_view_keyspace to allow MVs if RF=Racks
db: enforce rf-rack-validity for keyspaces with views
replica/db: add enforce_rf_rack_validity_for_keyspace helper
db: remove enforce parameter from check_rf_rack_validity
test: adjust test to not break rf-rack validity
The doc about DDL statements claims that an `ALTER KEYSPACE` will fail
in the presence of an ongoing global topology operation.
This limitation was specifically referring to RF changes, which Scylla
implements as global topology requests (`keyspace_rf_change`), and it
was true when it was first introduced (1b913dd880) because there was
no global topology request queue at that time, so only one ongoing
global request was allowed in the cluster.
This limitation was lifted with the introduction of the global topology
request queue (6489308ebc), and it was re-introduced again very
recently (2e7ba1f8ce) in a slightly different form; it now applies only
to RF changes (not to any request type) and only those that affect the
same keyspace. None of these two changes were ever reflected in the doc.
Synchronize the doc with the current state.
Fixes#27776.
Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com>
Closesscylladb/scylladb#27786
Update the documentation about restrictions to tablets keyspaces related
to RF-rack.
* MV/SI require the keyspace to be RF-rack-valid
* topology operations are restricted if a keyspace has views to preserve
RF-rack-validity
Currently some things are not supported for colocated tables: it's not
possible to repair a colocated table, and due to this it's also not
possible to use the tombstone_gc=repair mode on a colocated table.
Extend the documentation to explain what colocated tables are and
document these restrictions.
Fixesscylladb/scylladb#27261Closesscylladb/scylladb#27516
This commit fixes the information about object storage:
- Object storage configuration is no longer marked as experimental.
- Redundant information has been removed from the description.
- Information related to object storage for SStabels has been removed
as the feature is not working.
Fixes https://github.com/scylladb/scylladb/issues/26985Closesscylladb/scylladb#26987
This patch series re-enables support for speculative retry values `0` and `100`. These values have been supported some time ago, before [schema: fix issue 21825: add validation for PERCENTILE values in speculative_retry configuration. #21879
](https://github.com/scylladb/scylladb/pull/21879). When that PR prevented using invalid `101PERCENTILE` values, valid `100PERCENTILE` and `0PERCENTILE` value were prevented too.
Reproduction steps from [[Bug]: drop schema and all tables after apply speculative_retry = '99.99PERCENTILE' #26369](https://github.com/scylladb/scylladb/issues/26369) are unable to reproduce the issue after the fix. A test is added to make sure the inclusive border values `0` and `100` are supported.
Documentation is updated to give more information to the users. It now states that these border values are inclusive, and also that the precision, with automatic rounding, is 1 decimal digit.
Fixes#26369
This is a bug fix. If at any time a client tries to use value >= 99.5 and < 100, the raft error will happen. Backport is needed. The code which introduced inconsistency is introduced in 2025.2, so no backporting to 2025.1.
Closesscylladb/scylladb#26909
* github.com:scylladb/scylladb:
test: cqlpy: add test case for non-numeric PERCENTILE value
schema: speculative_retry: update exception type for sstring ops
docs: cql: ddl.rst: update speculative-retry-options
test: cqlpy: add test for valid speculative_retry values
schema: speculative_retry: allow 0 and 100 PERCENTILE values
Clarify how the value of `XPERCENTILE` is handled:
- Values 0 and 100 are supported
- The percentile value is rounded to the nearest 0.1 (1 decimal place)
Refs #26369
Auto-exands numeric RF in CREATE/ALTER KEYSPACE statements for
new DCs specified in the statement.
Doesn't auto-expand existing options, as the rack choice may not be in
line with current replica placement. This requires co-locating tablet
replicas, and tracking of co-location state, which is not implemented yet.
Signed-off-by: Tomasz Grabiec <tgrabiec@scylladb.com>
We want to add strongly consistent tables as an option. We will have
two kind of strongly consistent tables: globally consistent and locally
consistent. The former means that requests from all DCs will be globally
linearisable while the later - only requests to the same DCs will be
linearisable. To allow configuring all the possibilities the patch
adds new parameter to a keyspace definition "consistency" that can be
configured to be `eventual`, `global` or `local`. Non eventual setting
is supported for tablets enabled keyspaces only. Since we want to start
with implementing local consistency configuring global consistency will
result in an error for now.
This patch updates the create keyspace statement docs. It explains how
the `replication` option in the create keyspace statement is now optional,
and behaves the same as if we specified an empty set as following:
`WITH replication = {}`.
An example with no `replication` option specified has also been added.
Refs #25145
Update create-keyspace-statement section of ddl.rst since replication factor is no longer mandatory.
Add an example for keyspace creation without specifying replication factor.
Add an example for keyspace creation without specifying both `class` and replication factor.
Refs: #16028
Update create-keyspace-statement section of ddl.rst since `class` is no longer mandatory.
Add an example for keyspace creation without specifying `class`.
Refs: #16029
This commit removes the Non-Reserved CQL Keywords and Reserved CQL Keywords pages-keyword
as that content is already covered on the Appendices page.
Redirections are added to avoid 404s for the removed pages.
In addition, the Appendices page title is extended with "Reserved CQL Keywords and Types"
to help users understand what those appendices are about.
Fixes https://github.com/scylladb/scylladb/issues/24319Closesscylladb/scylladb#24320
This commit increases the maximum length of names for keyspaces, tables, materialized views, and indexes from 48 to 192 bytes.
The previous 48-bytes limit was inherited from Cassandra 3 for compatibility. However, this validation was removed in Cassandra 4 and 5 (see CASSANDRA-20389)
and some usage scenarios (such as some feature store workflows generating long table names) now depend on this relaxed constraint.
This change brings ScyllaDB's behavior in line with modern Cassandra versions and better supports these use cases.
The new limit of 192 bytes is derived from underlying filesystem limitations to prevent runtime errors when creating directories for table data.
When a new table is created, ScyllaDB generates a directory for its SSTables. The directory name is constructed from the table name, a dash, and a 32-character UUID.
For a CDC-enabled table, an associated log table is also created, which has the suffix `_scylla_cdc_log` appended to its name.
The directory name for this log table becomes the longest possible representation.
Additionally we reserve 15 bytes for future use, allowing for potential future extensions without breaking existing schemas.
To guarantee that directory creation never fails due to exceeding filesystem name limits, the maximum name length is calculated as follows:
255 bytes (common filesystem limit for a path component)
- 32 bytes (for the 32-character UUID string)
- 1 byte (for the '-' separator)
- 15 bytes (for the '_scylla_cdc_log' suffix)
- 15 bytes (reserved for future use)
----------
= 192 bytes (Maximum allowed name length)
This calculation is similar in principle to the one proposed for Cassandra to fix related directory creation failures (see apache/cassandra/pull/4038).
This patch also updates/adds all associated tests to validate the new 192-byte limit.
The documentation has been updated accordingly.
Current protocol extension that sends tablet info to drivers only does
that if the driver selects a non-replica coordinator for a routable
request. It works well if some node on the replica list is replaced by
other node, or if some replicas are removed from the list. Driver will
at some point send a request to stale replica, and receive new list in
response.
The issue is with extending the list with new replicas. In that case old
replicas are all still correct, so driver will not select any wrong
replica, and will not receive the new list. As far as I know that only
scenario where this could happen is RF increase.
It could be to some degree worked around in the drivers, but it would
add significant complexity (definitely more than any other invalidations
we introduced) while still not being ideal solution. This scenario
should be rare enough, and the consequences of not handling it minor
enough (new replicas not being used as coordinators) that it does not
warrant driver-side solution. Instead this commit adds info about this
to documentation, advising users to restart applications after replica
lists are extended.
It is worth noting that if new tablet feedback protocol extension is
implemented then this problem goes away. See issue #21664.
Closesscylladb/scylladb#23447
We introduce a new term in the glossary: RF-rack-valid keyspace.
We also highlight in our user documentation that all keyspaces
must remain RF-rack-valid throughout their lifetime, and failing
to guarantee that may result in data inconsistencies or other
issues. We base that information on our experience with materialized
views in keyspaces using tablets, even though they remain
an experimental feature.
Along with the new term, we introduce a new configuration option
called `rf_rack_valid_keyspaces`, which, when enabled, will enforce
preserving all keyspaces RF-rack-valid. That functionality will be
implemented in upcoming commits. For now, we materialize the
restriction in form of a named requirement: a function verifying
that the passed keyspace is RF-rack-valid.
The option is disabled by default. That will change once we adjust
the existing tests to the new semantics. Once that is done, the option
will first be enabled by default, and then it will be removed.
Fixesscylladb/scylladb#20356
This commit adds a link to the Limitations section on the Tablets page
to the CQL pag, the tablets option.
This is actually the place where the user will need the information:
when creating a keyspace.
In addition, I've reorganized the section for better readability
(otherwise, the section about limitations was easy to miss)
and moved the section up on the page.
Note that I've removed the updated content from the `_common` folder
(which I deleted) to the .rst page - we no longer split OSS and Enterprise,
so there's no need to keep using the `scylladb_include_flag` directive
to include OSS- and Ent-specific content.
Fixes https://github.com/scylladb/scylladb/issues/22892
Fixes https://github.com/scylladb/scylladb/issues/22940Closesscylladb/scylladb#22939
Use the keyspace initial_tablets for min_tablet_count, if the latter
isn't set, then take the maximum of the option-based tablet counts:
- min_tablet_count
- and expected_data_size_in_gb / target_tablet_size
- min_per_shard_tablet_count (via
calculate_initial_tablets_from_topology)
If none of the hints produce a positive tablet_count,
fall back to calculate_initial_tablets_from_topology * initial_scale.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Per-table hints should be used instead.
Note: the warning is produced by check_against_restricted_replication_strategies
which is called also from alter_keyspace_statement.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Unlike with vnodes, each tablet is served only by a single
shard, and it is associated with a memtable that, when
flushed, it creates sstables which token-range is confined
to the tablet owning them.
On one hand, this allows for far better agility and elasticity
since migration of tablets between nodes or shards does not
require rewriting most if not all of the sstables, as required
with vnodes (at the cleanup phase).
Having too few tablets might limit performance due not
being served by all shards or by imbalance between shards
caused by quantization. The number of tabelts per table has to be
a power of 2 with the current design, and when divided by the
number of shards, some shards will serve N tablets, while others
may serve N+1, and when N is small N+1/N may be significantly
larger than 1. For example, with N=1, some shards will serve
2 tablet replicas and some will serve only 1, causing an imbalance
of 100%.
Now, simply allocating a lot more tablets for each table may
theoretically address this problem, but practically:
a. Each tablet has memory overhead and having too many tablets
in the system with many tables and many tablets for each of them
may overwhelm the system's and cause out-of-memory errors.
b. Too-small tablets cause a proliferation of small sstables
that are less efficient to acces, have higher metadata overhead
(due to per-sstable overhead), and might exhaust the system's
open file-descriptors limitations.
The options introduced in this change can help the user tune
the system in two ways:
1. Sizing the table to prevent unnecessary tablet splits
and migrations. This can be done when the table is created,
or later on, using ALTER TABLE.
2. Controlling min_per_shard_tablet_count to improve
tablet balancing, for hot tables.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Add a paragraph documenting the decision to deprecate
the COMPACT STORAGE feature, and instruct the user
how to enable the feature despite that.
Note that we don't have an official migration strategy
for users like `DROP COMPACT STORAGE`, which is not
implemented at this time (See #3882).
Fixes#16375
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
ICS is a compaction strategy that inherits size tiered properties --
therefore it's write optimized too -- but fixes its space overhead of
100% due to input files being only released on completion. That's
achieved with the concept of sstable run (similar in concept to LCS
levels) which breaks a large sstable into fixed-size chunks (1G by
default), known as run fragments. ICS picks similar-sized runs
for compaction, and fragments of those runs can be released
incrementally as they're compacted, reducing the space overhead
to about (number_of_input_runs * 1G). This allows user to increase
storage density of nodes (from 50% to ~80%), reducing the cost of
ownership.
NOTE: test_system_schema_version_is_stable adjusted to account for batchlog
using IncrementalCompactionStrategy
contains:
compaction/: added incremental_compaction_strategy.cc (.hh), incremental_backlog_tracker.cc (.hh)
compaction/CMakeLists.txt: include ICS cc files
configure.py: changes for ICS files, includes test
db/legacy_schema_migrator.cc / db/schema_tables.cc: fallback to ICS when strategy is not supported
db/system_keyspace: pick ICS for some system tables
schema/schema.hh: ICS becomes default
test/boost: Add incremental_compaction_test.cc
test/boost/sstable_compaction_test.cc: ICS related changes
test/cqlpy/test_compaction_strategy_validation.py: ICS related changes
docs/architecture/compaction/compaction-strategies.rst: changes to ICS section
docs/cql/compaction.rst: changes to ICS section
docs/cql/ddl.rst: adds reference to ICS options
docs/getting-started/system-requirements.rst: updates sentence mentioning ICS
docs/kb/compaction.rst: changes to ICS section
docs/kb/garbage-collection-ics.rst: add file
docs/kb/index.rst: add reference to <garbage-collection-ics>
docs/operating-scylla/procedures/tips/production-readiness.rst: add ICS section
some relevant commits throughout the ICS history:
commit 434b97699b39c570d0d849d372bf64f418e5c692
Merge: 105586f747 30250749b8
Author: Paweł Dziepak <pdziepak@scylladb.com>
Date: Tue Mar 12 12:14:23 2019 +0000
Merge "Introduce Incremental Compaction Strategy (ICS)" from Raphael
"
Introduce new compaction strategy which is essentially like size tiered
but will work with the existing incremental compaction. Thus incremental
compaction strategy.
It works like size tiered, but each element composing a tier is a sstable
run, meaning that the compaction strategy will look for N similar-sized
sstable runs to compact, not just individual sstables.
Parameters:
* "sstable_size_in_mb": defines the maximum sstable (fragment) size
composing
a sstable run, which impacts directly the disk space requirement which is
improved with incremental compaction.
The lower the value the lower the space requirement for compaction because
fragments involved will be released more frequently.
* all others available in size tiered compaction strategy
HOWTO
=====
To change an existing table to use it, do:
ALTER TABLE mykeyspace.mytable WITH compaction =
{'class' : 'IncrementalCompactionStrategy'};
Set fragment size:
ALTER TABLE mykeyspace.mytable WITH compaction =
{'class' : 'IncrementalCompactionStrategy', 'sstable_size_in_mb' : 1000 }
"
commit 94ef3cd29a196bedbbeb8707e20fe78a197f30a1
Merge: dca89ce7a5 e08ef3e1a3
Author: Avi Kivity <avi@scylladb.com>
Date: Tue Sep 8 11:31:52 2020 +0300
Merge "Add feature to limit space amplification in Incremental Compaction" from Raphael
"
A new option, space_amplification_goal (SAG), is being added to ICS. This option
will allow ICS user to set a goal on the space amplification (SA). It's not
supposed to be an upper bound on the space amplification, but rather, a goal.
This new option will be disabled by default as it doesn't benefit write-only
(no overwrites) workloads and could hurt severely the write performance.
The strategy is free to delay triggering this new behavior, in order to
increase overall compaction efficiency.
The graph below shows how this feature works in practice for different values
of space_amplification_goal:
https://user-images.githubusercontent.com/1409139/89347544-60b7b980-d681-11ea-87ab-e2fdc3ecb9f0.png
When strategy finds space amplification crossed space_amplification_goal, it
will work on reducing the SA by doing a cross-tier compaction on the two
largest tiers. This feature works only on the two largest tiers, because taking
into account others, could hurt the compaction efficiency which is based on
the fact that the more similar-sized sstables are compacted together the higher
the compaction efficiency will be.
With SAG enabled, min_threshold only plays an important role on the smallest
tiers, given that the second-largest tier could be compacted into the largest
tier for a space_amplification_goal value < 2.
By making the options space_amplification_goal and min_threshold independent,
user will be able to tune write amplification and space amplification, based on
the needs. The lower the space_amplification_goal the higher the write
amplification, but by increasing the min threshold, the write amplification
can be decreased to a desired amount.
"
commit 7d90911c5fb3fa891ad64a62147c3a6ca26d61b1
Author: Raphael S. Carvalho <raphaelsc@scylladb.com>
Date: Sat Oct 16 13:41:46 2021 -0300
compaction: ICS: Add garbage collection
Today, ICS lacks an approach to persist expired tombstones in a timely manner,
which is a problem because accumulation of tombstones are known to affecting
latency considerably.
For an expired tombstone to be purged, it has to reach the top of the LSM tree
and hope that older overlapping data wasn't introduced at the bottom.
The condition are there and must be satisfied to avoid data resurrection.
STCS, today, has an inefficient garbage collection approach because it only
picks a single sstable, which satisfies the tombstone density threshold and
file staleness. That's a problem because overlapping data either on same tier
or smaller tiers will prevent tombstones from being purged. Also, nothing is
done to push the tombstones to the top of the tree, for the conditions to be
eventually satisfied.
Due to incremental compaction, ICS can more easily have an effecient GC by
doing cross-tier compaction of relevant tiers.
The trigger will be file staleness and tombstone density, which threshold
values can be configured by tombstone_compaction_interval and
tombstone_threshold, respectively.
If ICS finds a tier which meets both conditions, then that tier and the
larger[1] *and* closest-in-size[2] tier will be compacted together.
[1]: A larger tier is picked because we want tombstones to eventually reach the
top of the tree.
[2]: It also has to be the closest-in-size tier as the smaller the size
difference the higher the efficiency of the compaction. We want to minimize
write amplification as much as possible.
The staleness condition is there to prevent the same file from being picked
over and over again in a short interval.
With this approach, ICS will be continuously working to purge garbage while
not hurting overall efficiency on a steady state, as same-tier compactions are
prioritized.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Message-Id: <20211016164146.38010-1-raphaelsc@scylladb.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#22063
Although `crc_check_chance` is accepted as a configuration option in ScyllaDB,
the value is currently ignored during runtime. This change makes this behavior
explicit in the documentation to prevent potential user misunderstandings.
Changes:
- Explicitly document that the option is currently a no-op
- Provide clear guidance on the current implementation
- Prevent confusion about the option's actual functionality
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#21794
ScyllaDB doesn't support custom compressors. The available compressors
are the only available ones, not the default ones.
Adjust the text to reflect this.
Closesscylladb/scylladb#20225
This commit extracts the information about the default for tables in keyspace creation
to a separate file in the _common folder. The file is then included using
the scylladb_include_flag directive.
The purpose of this commit is to make it possible to include a different file
in the scylla-enterprise repo - with a different default.
Refs https://github.com/scylladb/scylla-enterprise/issues/4585Closesscylladb/scylladb#20181
This commit removes the information that tablets are an experimental feature
from the CREATE KEYSPACE section.
In addition, it removes the notes and cautions that are redundant when
a feature is GA, especially the information and warnings about the future
plans.
Fixes https://github.com/scylladb/scylladb/issues/18670Closesscylladb/scylladb#19063
This change supports changing replication factor in tablets-enabled keyspaces.
This covers both increasing and decreasing the number of tablets replicas through
first building topology mutations (`alter_keyspace_statement.cc`) and then
tablets/topology/schema mutations (`topology_coordinator.cc`).
For the limitations of the current solution, please see the docs changes attached to this PR.
Fixes: #16129Closesscylladb/scylladb#16723
* github.com:scylladb/scylladb:
test: Do not check tablets mutations on nodes that don't have them
test: Fix the way tablets RF-change test parses mutation_fragments
test/tablets: Unmark RF-changing test with xfail
docs: document ALTER KEYSPACE with tablets
Return response only when tablets are reallocated
cql-pytest: Verify RF is changes by at most 1 when tablets on
cql3/alter_keyspace_statement: Do not allow for change of RF by more than 1
Reject ALTER with 'replication_factor' tag
Implement ALTER tablets KEYSPACE statement support
Parameterize migration_manager::announce by type to allow executing different raft commands
Introduce TABLET_KEYSPACE event to differentiate processing path of a vnode vs tablets ks
Extend system.topology with 3 new columns to store data required to process alter ks global topo req
Allow query_processor to check if global topo queue is empty
Introduce new global topo `keyspace_rf_change` req
New raft cmd for both schema & topo changes
Add storage service to query processor
tablets: tests for adding/removing replicas
tablet_allocator: make load_balancer_stats_manager configurable by name
