Most other services have their configs, rpair still uses global
db::config.
Add an empty config struct to repair_service to carry db::config options
the repair service needs.
Subsequent patches will populate the struct with options.
The config is created in main.cc as sharded_parameter because all future
options are live-updateable and should capture theirs source from
db::config on correct shard.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The endpoint URL remains intact. Having it next to another toppartitions
endpoint (the /column_family/toppartitions one) is natural.
This endpoint only needs sharded<replica::database>&, grabs it from
http_context and doesn't use any other service. In column_family.cc the
database reference is already available as a parameter. Once more user
of http_context.db is gone.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Closesscylladb/scylladb#28996
The test in question uses several helpers from the backup sute, but it doesn't really need them -- the operations it want to perform can be performed with standard pylib methods. "While at it" also collect some dangling effectively unused local variables from this test (these were apparently left from backup tests this one was copied-and-reworked from)
Enhancing tests, not backporting
Closesscylladb/scylladb#29130
* github.com:scylladb/scylladb:
test/refresh: Simplify refresh invocation
test/refresh: Remove r_servers alias for servers
test/refresh: Replace check_mutation_replicas with a plain CQL SELECT
test/refresh: Inline keyspace/table/data setup in test_refresh_deletes_uploaded_sstables
test/refresh: Prepare indentation for new_test_keyspace in test_refresh_deletes_uploaded_sstables
test/refresh: Decouple test_refresh_deletes_uploaded_sstables from backup tests
test/refresh: Remove unused wait_for_cql_and_get_hosts import
Two issues found in the lister returned by gs_client_wrapper::make_object_lister()
Lister can report EOF too early in case filter is active, another one is potential vector out-of-bounds access
Fixes#29058
The code appeared in 2026.1, worth fixing it there as well
Closesscylladb/scylladb#29059
* github.com:scylladb/scylladb:
sstables: Fix object storage lister not resetting position in batch vector
sstables: Fix object storage lister skipping entries when filter is active
When it deadlocks, groups stop merging and compaction group merge
backlog will run-away.
Also, graceful shutdown will be blocked on it.
Found by flaky unit test
test_merge_chooses_best_replica_with_odd_count, which timed-out in 1
in 100 runs.
Reason for deadlock:
When storage groups are merged, the main compaction group of the new
storage group takes a compaction lock, which is appended to
_compaction_reenablers_for_merging, and released when the merge
completion fiber is done with the whole batch.
If we accumulate more than 1 merge cycle for the fiber, deadlock
occurs. Lock order will be this
Initial state:
cg0: main
cg1: main
cg2: main
cg3: main
After 1st merge:
cg0': main [locked], merging_groups=[cg0.main, cg1.main]
cg1': main [locked], merging_groups=[cg2.main, cg3.main]
After 2nd merge:
cg0'': main [locked], merging_groups=[cg0'.main [locked], cg0.main, cg1.main, cg1'.main [locked], cg2.main, cg3.main]
merge completion fiber will try to stop cg0'.main, which will be
blocked on compaction lock. which is held by the reenabler in
_compaction_reenablers_for_merging, hence deadlock.
The fix is to wait for background merge to finish before we start the
next merge. It's achieved by holding old erm in the background merge,
and doing a topology barrier from the merge finalizing transition.
Background merge is supposed to be a relatively quick operation, it's
stopping compaction groups. So may wait for active requests. It
shouldn't prolong the barrier indefinitely.
Tablet tests which trigger merge need to be adjusted to call the
barrier, otherwise they will be vulnerable to the deadlock.
Fixes SCYLLADB-928
Backport to >= 2025.4 because it's the earliest vulnerable due to f9021777d8.
Closesscylladb/scylladb#29007
* github.com:scylladb/scylladb:
tablets: Fix deadlock in background storage group merge fiber
replica: table: Propagate old erm to storage group merge
test: boost: tablets_test: Save tablet metadata when ACKing split resize decision
storage_service: Extract local_topology_barrier()
This patch series introduces a new documentation for exiting guardrails.
Moreover:
- Warning / failure messages of recently added write CL guardrails (SCYLLADB-259) are rephrased, so all guardrails have similar messages.
- Some new tests are added, to help verify the correctness of the documentation and avoid situations where the documentation and implementation diverge.
Fixes: [SCYLLADB-257](https://scylladb.atlassian.net/browse/SCYLLADB-257)
No backport, just new docs and tests.
[SCYLLADB-257]: https://scylladb.atlassian.net/browse/SCYLLADB-257?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQClosesscylladb/scylladb#29011
* github.com:scylladb/scylladb:
test: add new guardrail tests matching documentation scenarios
test: add metric assertions to guardrail replication strategy tests
test: use regex matching in guardrail replication strategy tests
test: extract ks_opts helper in test_guardrail_replication_strategy
docs: document CQL guardrails
cql: improve write consistency level guardrail messages
This PR enables the node_exporter systemd collector and configures the unit whitelist to include scylla-server.service and systemd-coredump services.
**Motivation**: We currently lack visibility into system-level service states, which is critical for diagnosing stability issues.
This configuration enables two specific use cases:
- Detecting Coredump Loops: We encounter scenarios where ScyllaDB enters a restart loop. To pinpoint SIGSEGV (coredumps) as the root cause, we need to track when the systemd-coredump service becomes active, indicating a dump is being processed.
- Identifying Startup Failures: We need to detect when the scylla-server unit enters a failed state. This is essential for catching unrecoverable errors (e.g., corrupted commitlogs or configuration bugs) that prevent the server from starting.
example of promql queries:
- `node_systemd_unit_state{name=~"systemd-coredump@.*", state="active"} == 1`
- `node_systemd_unit_state{name="scylla-server.service", state="failed"} == 1`
Closes#28402
reader_concurrency_semaphore::signal() guards against available
resources exceeding the initial limit after a signal, which would
indicate a bug such as double-returning resources. It reports the
issue via on_internal_error_noexcept and clamps resources back to
the initial values. However, before this commit there were no tests
that verified this behavior, so bugs like SCYLLADB-1014 went
undetected.
Add a test that artificially signals resources that were never
consumed and verifies that signal() detects the negative leak and
clamps available resources back to the initial limit.
Refs: SCYLLADB-1014
Fixes: SCYLLADB-1031
Closesscylladb/scylladb#28993
Since 7564a56dc8, all tables default to
repair-mode tombstone-gc, which is identical to immediate-mode for RF=1
tables. Consequently the tombstones written by the tests in this test
file are immediately collectible and with some unlucky timing, some of
them can be collected before the end of the test, failing the empty-page
prefix check because the empty pages prefix will be smaller than
expected based on the number of tombstones written.
Disable tombstone-gc to remove this source of flakyness.
Fixes: SCYLLADB-1062
Closesscylladb/scylladb#29077
The test has expectation w.r.t which write makes it to which nodes:
* inserts make it to all nodes
* delete makes it to all-1 (QUORUM) node
However, this was not expressed with CL, and the default CL=ONE allowed
for some nodes missing the writes and this violating the tests
expectations on what data is persent on which nodes. This resulted on
the test being flaky and failing on the data checks.
Use explicit CL for the ingestion to prevent this.
The improvements to the test introduced in
a8dd13731f was of great help in
investigating this: traces are now available and the check happens after
the data was dumped to logs.
Fixes: SCYLLADB-870
Fixes: SCYLLADB-812
Fixes: SCYLLADB-1102
Closesscylladb/scylladb#29128
Introduce an initial and experimental implementation of an alternative log-structured storage engine for key-value tables.
Main flows and components:
* The storage is composed of 32MB files, each file divided to segments of size 128k. We write to them sequentially records that contain a mutation and additional metadata. Records are written to a buffer first and then written to the active segment sequentially in 4k sized blocks.
* The primary index in memory maps keys to their location on disk. It is a B-tree per-table that is ordered by tokens, similar to a memtable.
* On reads we calculate the key and look it up in the primary index, then read the mutation from disk with a single disk IO.
* On writes we write the record to a buffer, wait for it to be written to disk, then update the index with the new location, and free the previous record.
* We track the used space in each segment. When overwriting a record, we increase the free space counter for the segment of the previous record that becomes dead. We store the segments in a histogram by usage.
* The compaction process takes segments with low utilization, reads them and writes the live records to new segments, and frees the old segments.
* Segments are initially "mixed" - we write to the active segment records from all tables and all tablets. The "separator" process rewrites records from mixed segments into new segments that are organized by compaction groups (tablets), and frees the mixed segments. Each write is written to the active segment and to a separator buffer of the compaction group, which is eventually flushed to a new segment in the compaction group.
Currently this mode is experimental and requires an experimental flag to be enabled.
Some things that are not supported yet are strong consistency, tablet migration, tablet split/merge, big mutations, tombstone gc, ttl.
to use, add to config:
```
enable_logstor: true
experimental_features:
- logstor
```
create a table:
```
CREATE TABLE ks.t(pk int PRIMARY KEY, a int, v text) WITH storage_engine = 'logstor';
```
INSERT, SELECT, DELETE work as expected
UPDATE not supported yet
no backport - new feature
Closesscylladb/scylladb#28706
* github.com:scylladb/scylladb:
logstor: trigger separator flush for buffers that hold old segments
docs/dev: add logstor documentation
logstor: recover segments into compaction groups
logstor: range read
logstor: change index to btree by token per table
logstor: move segments to replica::compaction_group
db: update dirty mem limits dynamically
logstor: track memory usage
logstor: logstor stats api
logstor: compaction buffer pool
logstor: separator: flush buffer when full
logstor: hold segment until index updates
logstor: truncate table
logstor: enable/disable compaction per table
logstor: separator buffer pool
test: logstor: add separator and compaction tests
logstor: segment and separator barrier
logstor: separator debt controller
logstor: compaction controller
logstor: recovery: recover mixed segments using separator
logstor: wait for pending reads in compaction
logstor: separator
logstor: compaction groups
logstor: cache files for read
logstor: recovery: initial
logstor: add segment generation
logstor: reserve segments for compaction
logstor: index: buckets
logstor: add buffer header
logstor: add group_id
logstor: record generation
logstor: generation utility
logstor: use RIPEMD-160 for index key
test: add test_logstor.py
api: add logstor compaction trigger endpoint
replica: add logstor to db
schema: add logstor cf property
logstor: initial commit
db: disable tablet balancing with logstor
db: add logstor experimental feature flag
Trie-based sstable indexes are supposed to be (hopefully) a better default than the old BIG indexes.
Make the new format a new default for new clusters by naming ms in the default scylla.yaml.
New functionality. No backport needed.
This PR is basically Michał's one https://github.com/scylladb/scylladb/pull/26377, Jakub's https://github.com/scylladb/scylladb/pull/27332 fixing `sstables_manager::get_highest_supported_format()` and one test fix.
Closesscylladb/scylladb#28960
* github.com:scylladb/scylladb:
db/config: announce ms format as highest supported
db/config: enable `ms` sstable format by default
cluster/dtest/bypass_cache_test: switch from highest_supported_sstable_format to chosen_sstable_format
api/system: add /system/chosen_sstable_version
test/cluster/dtest: reduce num_tokens to 16
take_snapshot return values were unused so drop them. do_refresh was a
thin wrapper around load_new_sstables that added no logic; inline it
directly into the gather expression.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
The goal of test_refresh_deletes_uploaded_sstables is to verify that
sstables are removed from the upload directory after refresh. The replica
check was just a sanity guard; a simple SELECT of all keys is sufficient
and much lighter.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Replace create_dataset() with explicit keyspace creation via new_test_keyspace,
inline CREATE TABLE, and direct cql.run_async inserts — matching the pattern
used in do_test_streaming_scopes. This removes the last dependency on backup
helpers for dataset setup and makes the test self-contained.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Wrap the test body under if True: to pre-indent it, making the subsequent
patch that introduces new_test_keyspace a pure content change with no
whitespace noise.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Replace create_cluster() from object_store/test_backup.py with a plain
manager.servers_add(2) call. The test does not use object storage, so
there is no need to pull in the backup helper along with its config and
logging knobs.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
This PR fixes the Installation page:
- Replaces `http `with `https `in the download command.
- Replaces the Open Source example from the Installation section for CentOS (we overlooked this example before).
Fixes https://github.com/scylladb/scylladb/issues/29087
Fixes https://github.com/scylladb/scylladb/issues/29087
This update affects all supported versions and should be backported as a bug fix.
Closesscylladb/scylladb#29088
* github.com:scylladb/scylladb:
doc: remove the Open Source Example from Installation
doc: replace http with https in the installation instructions
The default 'cassandra' superuser was removed from ScyllaDB, which
broke PGO training. exec_cql.py relied on username/password auth
('cassandra'/'cassandra') to execute setup CQL scripts like auth.cql
and counters.cql.
Switch exec_cql.py to connect via the Unix domain maintenance socket
instead. The maintenance socket bypasses authentication, no credentials
are needed. Additionally, create the 'cassandra' superuser via the
maintenance socket during the populate phase, so that cassandra-stress
keeps working. cassandra-stress hardcodes user=cassandra password=cassandra.
Changes:
- exec_cql.py: replace host/port/username/password arguments with a
single --socket argument; add connect_maintenance_socket() with
wait ready logic
- pgo.py: add maintenance_socket_path() helper; update
populate_auth_conns() and populate_counters() to pass the socket
path to exec_cql.py
Fixes SCYLLADB-1070
Closesscylladb/scylladb#29081
Add tests for RF guardrails (min/max warn/fail, RF=0 bypass,
threshold=-1 disable, ALTER KEYSPACE) and write consistency level
guardrails to cover all scenarios described in guardrails.rst.
Test runtime (dev):
test_guardrail_replication_strategy - 6s
test_guardrail_write_consistency_level - 5s
Refs: SCYLLADB-257
Replace loose substring assertions with regex-based matching against
the exact server message formats. Add regex constants for all
guardrail messages and rewrite create_ks_and_assert_warnings_and_errors()
to verify count and content of warnings and failures.
Refs: SCYLLADB-257
The Web Installer page includes instructions to install the old pre-2025.1 Enterprise versions,
which are no longer supported (since we released 2026.1).
This commit removes those redundant and misleading instructions.
Fixes https://github.com/scylladb/scylladb/issues/29099Closesscylladb/scylladb#29103
This patchset migrates: query_all_directly_granted, query_all,
get_attribute, query_attribute_for_all functions to use cache
instead of doing CQL queries. It also includes some preparatory
work which fixes cache update order and triggering.
Main motivation behind this is to make sure that all calls
from service_level_controller::auth_integration are cached,
which we achieve here.
Alternative implementation could move the whole auth_integration
data into auth cache but since auth_integration manages also lifetime
and contains service levels specific logic such solution would be
too complex for little (if any) gain.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-159
Backport: no, not a bug
Closesscylladb/scylladb#28791
* github.com:scylladb/scylladb:
auth: switch query_attribute_for_all to use cache
auth: switch get_attribute to use cache
auth: cache: add heterogeneous map lookups
auth: switch query_all to use cache
auth: switch query_all_directly_granted to use cache
auth: cache: add ability to go over all roles
raft: service: reload auth cache before service levels
service: raft: move update_service_levels_effective_cache check
`storage_group_of()` sits on the replica-side token lookup hot path, yet it called `tablet_map::get_tablet_id_and_range_side()`, which always computes both the tablet id and the post-split range side — even though most callers only need the storage group id.
The range-side computation is only relevant when a storage group is in tablet splitting mode, but we were paying for it unconditionally on every lookup.
This series fixes that by:
1. Adding `tablet_map::get_tablet_range_side()` so the range side can be computed independently when needed.
2. Adding lazy `select_compaction_group()` overloads that defer the range-side computation until splitting mode is actually active.
3. Switching `storage_group_of()` to use the cheaper `get_tablet_id()` path, only computing the range side on demand.
Improvements. No backport is required.
Closesscylladb/scylladb#28963
* github.com:scylladb/scylladb:
replica/table: avoid computing token range side in storage_group_of() on hot path
replica/compaction_group: add lazy select_compaction_group() overloads
locator/tablets: add tablet_map::get_tablet_range_side()
Factor out ks_opts() to build keyspace options with tablets handling
and use it across all existing replication strategy guardrail tests.
No behavioral changes.
This facilitates further modification of the tests later in this
patch series.
Refs: SCYLLADB-257
After repair, the test does a major to compact all sstables into a
single one, so the results can be simply checked by a select from
mutation_fragments() query. Sometimes off-strategy happens parallel to
this major, so after the major there are still 2 sstables, resulting in
the test failing when checking that the query returns just a single row.
To fix, just use tablets for the test table, tablets don't use
off-strategy anymore.
Fixes: SCYLLADB-940
Closesscylladb/scylladb#29071
Previously the test test_interrupt_view_build_shard_registration stopped
the node ungracefully and used commitlog periodic mode to persist the
view build progress in a not very reliable way.
It can happen that due to timing issues, the view build progress is not
persisted, or some of it is persisted in a different ordering than
expected.
To make the test more reliable we change it to stop the node gracefully,
so the commitlog is persisted in a graceful and consistent way, without
using the periodic mode delay. We need to also change the injection for
the shutdown to not get stuck.
Fixes SCYLLADB-1005
Closesscylladb/scylladb#29008
As reported in SCYLLADB-1013, the directory lister must be closed also when an exception is thrown.
For example, see backtrace below:
```
seastar::on_internal_error(seastar::logger&, std::basic_string_view<char, std::char_traits<char>>) at ./build/release/seastar/./seastar/src/core/on_internal_error.cc:57
directory_lister::~directory_lister() at ./utils/lister.cc:77
replica::table::get_snapshot_details(std::filesystem::__cxx11::path, std::filesystem::__cxx11::path) (.resume) at ./replica/table.cc:4081
std::__n4861::coroutine_handle<seastar::internal::coroutine_traits_base<db::snapshot_ctl::table_snapshot_details>::promise_type>::resume() const at /usr/lib/gcc/x86_64-redhat-linux/15/../../../../include/c++/15/coroutine:247
(inlined by) seastar::internal::coroutine_traits_base<db::snapshot_ctl::table_snapshot_details>::promise_type::run_and_dispose() at ././seastar/include/seastar/core/coroutine.hh:129
seastar::reactor::task_queue::run_tasks() at ./build/release/seastar/./seastar/src/core/reactor.cc:2695
(inlined by) seastar::reactor::task_queue_group::run_tasks() at ./build/release/seastar/./seastar/src/core/reactor.cc:3201
seastar::reactor::task_queue_group::run_some_tasks() at ./build/release/seastar/./seastar/src/core/reactor.cc:3185
(inlined by) seastar::reactor::do_run() at ./build/release/seastar/./seastar/src/core/reactor.cc:3353
seastar::reactor::run() at ./build/release/seastar/./seastar/src/core/reactor.cc:3245
seastar::app_template::run_deprecated(int, char**, std::function<void ()>&&) at ./build/release/seastar/./seastar/src/core/app-template.cc:266
seastar::app_template::run(int, char**, std::function<seastar::future<int> ()>&&) at ./build/release/seastar/./seastar/src/core/app-template.cc:160
scylla_main(int, char**) at ./main.cc:756
```
Fixes: [SCYLLADB-1013](https://scylladb.atlassian.net/browse/SCYLLADB-1013)
* Requires backport to 2026.1 since the leak exists since 004c08f525
[SCYLLADB-1013]: https://scylladb.atlassian.net/browse/SCYLLADB-1013?atlOrigin=eyJpIjoiNWRkNTljNzYxNjVmNDY3MDlhMDU5Y2ZhYzA5YTRkZjUiLCJwIjoiZ2l0aHViLWNvbS1KU1cifQClosesscylladb/scylladb#29084
* github.com:scylladb/scylladb:
test/boost/database_test: add test_snapshot_ctl_details_exception_handling
table: get_snapshot_details: fix indentation inside try block
table: per-snapshot get_snapshot_details: fix typo in comment
table: per-snapshot get_snapshot_details: always close lister using try/catch
table: get_snapshot_details: always close lister using deferred_close
Run keyspace compaction asynchronously in
`test_tombstone_gc_correctness_during_tablet_split` and only await it
after `split_sstable_rewrite` is disabled.
The problem is that `keyspace_compaction()` starts with a flush, and that
flush can take around five seconds. During that window the split
compaction is stopped before major compaction is retried. The stop aborts
the in-flight major compaction attempt, then the split proceeds far enough
to enter the `split_sstable_rewrite` injection point.
At that point the test used to wait synchronously for major compaction to
finish, but major compaction cannot finish yet: when it retries, it needs
the same semaphore that is still effectively tied up behind the blocked
split rewrite. So the test waits for major compaction, while the split
waits for the injection to be released, and the code that would release
that injection never runs.
Starting major compaction as a task breaks that cycle. The test can first
disable `split_sstable_rewrite`, let the split get out of the way, and
only then wait for major compaction to complete.
Fixes https://scylladb.atlassian.net/browse/SCYLLADB-827.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#29066
During decommission, we first mark a topology request as done, then shut
down a node and in the following steps we remove node from the topology.
Thus, finished request does not imply that a node is removed from
the topology.
Due to that, in node_ops_virtual_task::wait, while gathering children
from the whole cluster, we may hit the connection exception - because
a node is still in topology, even though it is down.
Modify the get_children method to ignore the exception and warn
about the failure instead.
Keep token_metadata_ptr in get_children to prevent topology from changing.
Fixes: https://scylladb.atlassian.net/browse/SCYLLADB-867
Needs backports to all versions
Closesscylladb/scylladb#29035
* github.com:scylladb/scylladb:
tasks: fix indentation
tasks: do not fail the wait request if rpc fails
tasks: pass token_metadata_ptr to task_manager::virtual_task::impl::get_children
Document that `SELECT ... WHERE` clause currently accepts only conjunctions
of relations joined by `AND` (`OR` is not supported), and that
parentheses cannot be used to group boolean subexpressions.
Add an unsupported query example and point readers to equivalent `IN`
rewrites when applicable.
This problem has been raised by one of our users in
https://forum.scylladb.com/t/error-parsing-query-or-unsupported-statement/5299,
and while one could infer answer to user's question by looking at the
syntax of the `SELECT ... WHERE`, it's not immediately obvious to
non-advanced users, so clarifying these concepts is justified.
Fixes: SCYLLADB-1116
Closesscylladb/scylladb#29100
A compaction group has a separator buffer that holds the mixed segments
alive until the separator buffer is flushed. A mixed segment can be
freed only after all separator buffers that hold writes from the segment
are flushed.
Typically a separator buffer is flushed when it becomes full. However
it's possible for example that one compaction groups is filled slower
than others and holds many segments.
To fix this we trigger a separator flush periodically for separator
buffers that hold old segments. We track the active segment sequence
number and for each separator buffer the oldest sequence number it
holds.
Fix the logstor recovery to work with compaction groups. When recovering
a segment find its token range and add it to the appropriate compaction
groups. if it doesn't fit in a single compaction group then write each
record to its compaction group's separator buffer.
Change the primary index to be a btree that is ordered by token,
similarly to a memtable, and create a index per-table instead of a
single global index.
Add a segment_set member to replica::compaction_group that manages the
logstor segments that belong to the compaction group, similarly to how
it manages sstables. Add also a separator buffer in each compaction
group.
When writing a mutation to a compaction group, the mutation is written
to the active segment and to the separator buffer of the compaction
group, and when the separator buffer is flushed the segment is added to
the compaction_group's segment set.
when logstor is enabled, update the db dirty memory limits dynamically.
previously the threshold is set to 0.5 of the available memory, so 0.5
goes to memtables and 0.5 to others (cache).
when logstor is enabled, we calculate the available memory excluding
logstor, and divide it evenly between memtables and cache.
