TWCS tables require partition estimation adjustment as incoming streaming data can be segregated into the time windows.
Turns out we had two problems in this area that leads to suboptimal bloom filters.
1) With off-strategy enabled, data segregation is postponed, but partition estimation was adjusted as if segregation wasn't postponed. Solved by not adjusting estimation if segregation is postponed.
2) With off-strategy disabled, data segregation is not postponed, but streaming didn't feed any metadata into partition estimation procedure, meaning it had to assume the max windows input data can be segregated into (100). Solved by using schema's default TTL for a precise estimation of window count.
For the future, we want to dynamically size filters (see https://github.com/scylladb/scylladb/issues/2024), especially for TWCS that might have SSTables that are left uncompacted until they're fully expired, meaning that the system won't heal itself in a timely manner through compaction on a SSTable that had partition estimation really wrong.
Fixes https://github.com/scylladb/scylladb/issues/15704.
Closesscylladb/scylladb#15938
* github.com:scylladb/scylladb:
streaming: Improve partition estimation with TWCS
streaming: Don't adjust partition estimate if segregation is postponed
(cherry picked from commit 64d1d5cf62)
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#16671
Having values of the duration type is not allowed for clustering
columns, because duration can't be ordered. This is correctly validated
when creating a table but do not validated when we alter the type.
Fixes#12913Closesscylladb/scylladb#16022
(cherry picked from commit bd73536b33)
The implementation of "SELECT TOJSON(t)" or "SELECT JSON t" for a column
of type "time" forgot to put the time string in quotes. The result was
invalid JSON. This is patch is a one-liner fixing this bug.
This patch also removes the "xfail" marker from one xfailing test
for this issue which now starts to pass. We also add a second test for
this issue - the existing test was for "SELECT TOJSON(t)", and the second
test shows that "SELECT JSON t" had exactly the same bug - and both are
fixed by the same patch.
We also had a test translated from Cassandra which exposed this bug,
but that test continues to fail because of other bugs, so we just
need to update the xfail string.
The patch also fixes one C++ test, test/boost/json_cql_query_test.cc,
which enshrined the *wrong* behavior - JSON output that isn't even
valid JSON - and had to be fixed. Unlike the Python tests, the C++ test
can't be run against Cassandra, and doesn't even run a JSON parser
on the output, which explains how it came to enshrine wrong output
instead of helping to discover the bug.
Fixes#7988
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closesscylladb/scylladb#16121
(cherry picked from commit 8d040325ab)
reconcilable_result_builder passes range tombstone changes to _rt_assembler
using table schema, not query schema.
This means that a tombstone with bounds (a; b), where a < b in query schema
but a > b in table schema, will not be emitted from mutation_query.
This is a very serious bug, because it means that such tombstones in reverse
queries are not reconciled with data from other replicas.
If *any* queried replica has a row, but not the range tombstone which deleted
the row, the reconciled result will contain the deleted row.
In particular, range deletes performed while a replica is down will not
later be visible to reverse queries which select this replica, regardless of the
consistency level.
As far as I can see, this doesn't result in any persistent data loss.
Only in that some data might appear resurrected to reverse queries,
until the relevant range tombstone is fully repaired.
This series fixes the bug and adds a minimal reproducer test.
Fixes#10598Closesscylladb/scylladb#16003
* github.com:scylladb/scylladb:
mutation_query_test: test that range tombstones are sent in reverse queries
mutation_query: properly send range tombstones in reverse queries
(cherry picked from commit 65e42e4166)
There are two tests, test_read_all and test_read_with_partition_row_limits, which asserts on every page as well
as at the end that there are no misses whatsoever. This is incorrect, because it is possible that on a given page, not all shards participate and thus there won't be a saved reader on every shard. On the subsequent page, a shard without a reader may produce a miss. This is fine. Refine the asserts, to check that we have only as much misses, as many
shards we have without readers on them.
Fixes: https://github.com/scylladb/scylladb/issues/14087Closesscylladb/scylladb#15806
* github.com:scylladb/scylladb:
test/boost/multishard_mutation_query_test: fix querier cache misses expectations
test/lib/test_utils: add require_* variants for all comparators
(cherry picked from commit 457d170078)
When populating system keyspace the sstable_directory forgets to create upload/ subdir in the tables' datadir because of the way it's invoked from distributed loader. For non-system keyspaces directories are created in table::init_storage() which is self-contained and just creates the whole layout regardless of what.
This PR makes system keyspace's tables use table::init_storage() as well so that the datadir layout is the same for all on-disk tables.
Test included.
fixes: #15708closes: scylladb/scylla-manager#3603Closesscylladb/scylladb#15723
* github.com:scylladb/scylladb:
test: Add test for datadir/ layout
sstable_directory: Indentation fix after previous patch
db,sstables: Move storage init for system keyspace to table creation
(cherry picked from commit 7f81957437)
This PR contains several refactoring, related to truncation records handling in `system_keyspace`, `commitlog_replayer` and `table` clases:
* drop map_reduce from `commitlog_replayer`, it's sufficient to load truncation records from the null shard;
* add a check that `table::_truncated_at` is properly initialized before it's accessed;
* move its initialization after `init_non_system_keyspaces`
Closesscylladb/scylladb#15583
* github.com:scylladb/scylladb:
system_keyspace: drop truncation_record
system_keyspace: remove get_truncated_at method
table: get_truncation_time: check _truncated_at is initialized
database: add_column_family: initialize truncation_time for new tables
database: add_column_family: rename readonly parameter to is_new
system_keyspace: move load_truncation_times into distributed_loader::populate_keyspace
commitlog_replayer: refactor commitlog_replayer::impl::init
system_keyspace: drop redundant typedef
system_keyspace: drop redundant save_truncation_record overload
table: rename cache_truncation_record -> set_truncation_time
system_keyspace: get_truncated_position -> get_truncated_positions
The estimation assumes that size of other components are irrelevant,
when estimating the number of partitions for each output sstable.
The sstables are split according to the data file size, therefore
size of other files are irrelevant for the estimation.
With certain data models, like single-row partitions containing small
values, the index could be even larger than data.
For example, assume index is as large as data, then the estimation
would say that 2x more sstables will be generated, and as a result,
each sstable are underestimated to have 2x less keys.
Fix it by only accounting size of data file.
Fixes#15726.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#15727
Currently, when the test is executed too quickly, the timestamp
insterted into the 'my_table' table might be the same as the
timestamp used in the SELECT statement for comparison. However,
the statement only selects rows where the inserted timestamp
is strictly lower than current timestamp. As a result, when this
comparison fails, we may skip executing the following comparison,
which uses a user-defined function, due to which the statement
is supposed to fail with an error. Instead, the select statement
simply returns no rows and the test case fails.
To fix this, simply use the less or equal operator instead
of using the strictly less operator for comparing timestamps.
Fixes#15616Closesscylladb/scylladb#15699
The logger is not thread safe, so a multithreaded test can concurrently
write into the log, yielding unreadable XMLs.
Example:
boost/sstable_directory_test: failed to parse XML output '/scylladir/testlog/x86_64/release/xml/boost.sstable_directory_test.sstable_directory_shared_sstables_reshard_correctly.3.xunit.xml': not well-formed (invalid token): line 1, column 1351
The critical (today's unprotected) section is in boost/test/utils/xml_printer.hpp:
```
inline std::ostream&
operator<<( custom_printer<cdata> const& p, const_string value )
{
*p << BOOST_TEST_L( "<![CDATA[" );
print_escaped_cdata( *p, value );
return *p << BOOST_TEST_L( "]]>" );
}
```
The problem is not restricted to xml, but the unreadable xml file caused
the test to fail when trying to parse it, to present a summary.
New thread-safe variants of BOOST_REQUIRE and BOOST_REQUIRE_EQUAL are
introduced to help multithreaded tests. We'll start patching tests of
sstable_directory_test that will call BOOST_REQUIRE* from multiple
threads. Later, we can expand its usage to other tests.
Fixes#15654.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Closesscylladb/scylladb#15655
Consider the following code snippet:
```c++
future<> foo() {
semaphore.consume(1024);
}
future<> bar() {
return _allocating_section([&] {
foo();
});
}
```
If the consumed memory triggers the OOM kill limit, the semaphore will throw `std::bad_alloc`. The allocating section will catch this, bump std reserves and retry the lambda. Bumping the reserves will not do anything to prevent the next call to `consume()` from triggering the kill limit. So this cycle will repeat until std reserves are so large that ensuring the reserve fails. At this point LSA gives up and re-throws the `std::bad_alloc`. Beyond the useless time spent on code that is doomed to fail, this also results in expensive LSA compaction and eviction of the cache (while trying to ensure reserves).
Prevent this situation by throwing a distinct exception type which is derived from `std::bad_alloc`. Allocating section will not retry on seeing this exception.
A test reproducing the bug is also added.
Fixes: #15278Closesscylladb/scylladb#15581
* github.com:scylladb/scylladb:
test/boost/row_cache_test: add test_cache_reader_semaphore_oom_kill
utils/logalloc: handle utils::memory_limit_reached in with_reclaiming_disabled()
reader_concurrency_semaphore: use utils::memory_limit_reached exception
utils: add memory_limit_reached exception
We want to make table::_truncated_at optional, so that in
get_truncation_time we can assert that it is initialized.
For existing tables this initialisation will happen in
load_truncation_times function, and for new tables we
want to initialize it in add_column_family like we do
with mark_ready_for_writes.
Now add_column_family function has parameter 'readonly', which is
set by the callers to false if we are creating a fresh new table
and not loading it from sstables. In this commit we rename this
parameter to is_new and invert the passed values.
This will allow us in the next commit to initialize _truncated_at field
for new tables.
All `sstable_set_impl` subclasses/implementations already keep a `schema_ptr` so we can make `sstable_set_impl::make_incremental_selector` function return both the selector and the schema that's being used by it.
That way, we can use the returned schema in `sstable_set::make_incremental_selector` function instead of `sstable_set::_schema` field which makes the field unused and allows us to remove it alltogether and reduce the memory footprint of `sstable_set` objects.
Closesscylladb/scylladb#15570
* github.com:scylladb/scylladb:
sstable_set: Remove unused _schema field
sstable_set_impl: Return also schema from make_incremental_selector
Also rephase the messages a bit so they are more uniform.
The goal of this change is to make semaphore mismatches easier to
diagnose, by including the table name and the permit name in the
printout.
While at it, add a test for semaphore mismatch, it didn't have one.
Refs: #15485Closesscylladb/scylladb#15508
Tracing is one of two global service left out there with its starting and stopping being pretty hairy. In order to de-globalize it and keep its start-stop under control the existing start-stop sequence is worth cleaning. This PR
* removes create_ , start_ and stop_ wrappers to un-hide the global tracing_instance thing
* renames tracing::stop() to shutdown() as it's in fact shutdown
* coroutinizes start/shutdown/stop while at it
Squeezed parts from #14156 that don't reorder start-stop calls
Closesscylladb/scylladb#15611
* github.com:scylladb/scylladb:
main: Capture local tracing reference to stop tracing
tracing: Pack testing code
tracing: Remove stop_tracing() wrapper
tracing: Remove start_tracing() wrapper
tracing: Remove create_tracing() wrapper
tracing: Make shutdown() re-entrable
tracing: Coroutinize start/shutdown/stop
tracing: Rename helper's stop() to shutdown()
The test does (among other things) the following:
1. Create a cache reader with buffer of size 1 and fill the buffer.
2. Update the cache.
3. Check that the reader produces the first mutation as seen before
the update (because the buffer fill should have snapshotted the first
mutation), and produces other mutation as seen after the update.
However, the test is not guaranteed to stop after the update succeeds.
Even during a successful update, an allocation might have failed
(and been retried by an allocation_section), which will cause the
body of with_allocation_failures to run again. On subsequent runs
the last check (the "3." above) fails, because the first mutation
is snapshotted already with the new version.
Fix that.
Closesscylladb/scylladb#15634
There's a finally-chain stopping tracing out there, now it can just use
the deferred stop call and that's it
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
Check that the cache reader reacts correctly to semaphore's OOM kill
attempt, letting the read to fail, instead of going berserk, trying to
reserve more-and-more memory, until the reserve cannot be satisfied.
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>
That's needed for upcoming changes that will allow ICS to efficiently
retrieve sstable runs.
Next patch will remove candidates from compaction_strategy's interface
to retrieve candidates using this one instead.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
sstable_run may reject insertion of a sstable if it's going
to break the disjoint invariant of the run, but it's important
that the caller is aware of it, so it can act on it like
generating a new run id for the sstable so it can be inserted
in another run. the tag is important to avoid unknown
problems in this area.
Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com>
Currently the datadir is ignored.
Use it to construct the table's base path.
Fixesscylladb/scylladb#15418Closesscylladb/scylladb#15480
* github.com:scylladb/scylladb:
distributed_loader: populate_keyspace: access cf by ref
distributed_loader: table_populator: use datadir for base_path
distributed_loader: populate_keyspace: issue table mark_ready_for_writes after all datadirs are processed
distributed_loader: populate_keyspace: fixup indentation
distributed_loader: populate_keyspace: iterate over datadirs in the inner loop
test: sstable_directory_test: add test_multiple_data_dirs
table: init_storage: create upload and staging subdirs on all datadirs
in this series, we rename s3 credential related variable and option names so they are more consistent with AWS's official document. this should help with the maintainability.
Closesscylladb/scylladb#15529
* github.com:scylladb/scylladb:
main.cc: rename aws option
utils/s3/creds: rename aws_config member variables
- s/aws_key/aws_access_key_id/
- s/aws_secret/aws_secret_access_key/
- s/aws_token/aws_session_token/
rename them to more popular names, these names are also used by
boto's API. this should improve the readability and consistency.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Currently, mark_ready_for_writes is called too early,
after the first data dir is processed, then the next
datadir will hit an assert in `table::mark_ready_for_writes`.
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Add a basic regression test that starts the cql test env
with multiple data directories.
It fails without the previous patch:
table: init_storage: create upload and staging subdirs on all datadirs
Signed-off-by: Benny Halevy <bhalevy@scylladb.com>
Table properties validation is performed on statement execution.
Thus, when one attempts to create a table with invalid options,
an incorrect command gets committed in Raft. But then its
application fails, leading to a raft machine being stopped.
Check table properties when create and alter statements are prepared.
Fixes: #14710.
Closesscylladb/scylladb#15091
* github.com:scylladb/scylladb:
cql3: statements: delete execute override
cql3: statements: call check_restricted_table_properties in prepare
cql3: statements: pass data_dictionary::database to check_restricted_table_properties
Off-strategy suffers with a 100% space overhead, as it adopted
a sort of all or nothing approach. Meaning all input sstables,
living in maintenance set, are kept alive until they're all
reshaped according to the strategy criteria.
Input sstables in off-strategy are very likely to be mostly disjoint,
so it can greatly benefit from incremental compaction.
The incremental compaction approach is not only good for
decreasing disk usage, but also memory usage (as metadata of
input and output live in memory), and file desc count, which
takes memory away from OS.
Turns out that this approach also greatly simplifies the
off-strategy impl in compaction manager, as it no longer have
to maintain new unused sstables and mark them for
deletion on failure, and also unlink intermediary sstables
used between reshape rounds.
Fixes https://github.com/scylladb/scylladb/issues/14992.
Closesscylladb/scylladb#15400
* github.com:scylladb/scylladb:
test: Verify that off-strategy can do incremental compaction
compaction: Clear pending_replacement list when tombstone GC is disabled
compaction: Enable incremental compaction on off-strategy
compaction: Extend reshape type to allow for incremental compaction
compaction: Move reshape_compaction in the source
compaction: Enable incremental compaction only if replacer callback is engaged
The S3 uploading sink needs to collect buffers internally before sending them out, because the minimal upload-able part size is 5Mb. When the necessary amount of bytes is accumulated, the part uploading fibers starts in the background. On flush the sink waits for all the fibers to complete and handles failure of any.
Uploading parallelism is nowadays limited by the means of the http client max-connections parameter. However, when a part uploading fibers waits for it connection it keeps the 5Mb+ buffers on the request's body, so even though the number of uploading parts is limited, the number of _waiting_ parts is effectively not.
This PR adds a shard-wide limiter on the number of background buffers S3 clients (and theirs http clients) may use.
Closesscylladb/scylladb#15497
* github.com:scylladb/scylladb:
s3::client: Track memory in client uploads
code: Configure s3 clients' memory usage
s3::client: Construct client with shared semaphore
sstables::storage_manager: Introduce config
Table properties validation is performed on statement execution.
Thus, when one attempts to create a table with invalid options,
an incorrect command gets committed in Raft. But then its
application fails, leading to a raft machine being stopped.
Check table properties when create and alter statements are prepared.
The error is no longer returned as an exceptional future, but it
is thrown. Adjust the tests accordingly.
when accessing AWS resources, uses are allowed to long-term security
credentials, they can also the temporary credentials. but if the latter
are used, we have to pass a session token along with the keys.
see also https://docs.aws.amazon.com/IAM/latest/UserGuide/id_credentials_temp_use-resources.html
so, if we want to programatically get authenticated, we need to
set the "x-amz-security-token" header,
see
https://docs.aws.amazon.com/AmazonS3/latest/userguide/RESTAuthentication.html#UsingTemporarySecurityCredentials
so, in this change, we
1. add another member named `token` in `s3::endpoint_config::aws_config`
for storing "AWS_SESSION_TOKEN".
2. populate the setting from "object_storage.yaml" and
"$AWS_SESSION_TOKEN" environment variable.
3. set "x-amz-security-token" header if
`s3::endpoint_config::aws_config::token` is not empty.
this should allow us to test s3 client and s3 object store backend
with S3 bucket, with the temporary credentials.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#15486
Sstables in transitional states are marked with the respective 'status' in the registry. Currently there are two of such -- 'creating' and 'removing'. And the 'sealed' status for sstables in use.
On boot the distributed loader tries to garbage collect the dangling sstables. For filesystem storage it's done with the help of temorary sstables' dirs and pending deletion logs. For s3-backed sstables, the garbage collection means fetching all non-sealed entries and removing the corresponding objects from the storage.
Test included (last patch)
fixes#13024Closesscylladb/scylladb#15318
* github.com:scylladb/scylladb:
test: Extend object_store test to validate GC works
sstable_directory: Garbage collect S3 sstables on reboot
sstable_directory: Pass storage to garbage_collect()
sstable_directory: Create storage instance too
This sets the real limits on the memory semaphore.
- scylla sets it to 1% of total memory, 10Mb min, 100Mb max
- tests set it to 16Mb
- perf test sets it to all available memory
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
The semaphore will be used to cap memory consumption by client. This
patch makes sure the reference to a semaphore exists as an argument to
client's constructor, not more than that.
In scylla binary, the semaphore sits on storage_manager. In tests the
semaphore is some local object. For now the semaphore is unused and is
initialized locked as this patch just pushes the needed argument all the
way around, next patches will make use of it.
Signed-off-by: Pavel Emelyanov <xemul@scylladb.com>
When performing a schema change through group 0, extend the schema mutations with a version that's persisted and then used by the nodes in the cluster in place of the old schema digest, which becomes horribly slow as we perform more and more schema changes (#7620).
If the change is a table create or alter, also extend the mutations with a version for this table to be used for `schema::version()`s instead of having each node calculate a hash which is susceptible to bugs (#13957).
When performing a schema change in Raft RECOVERY mode we also extend schema mutations which forces nodes to revert to the old way of calculating schema versions when necessary.
We can only introduce these extensions if all of the cluster understands them, so protect this code by a new cluster/schema feature, `GROUP0_SCHEMA_VERSIONING`.
Fixes: #7620Fixes: #13957Closesscylladb/scylladb#15331
* github.com:scylladb/scylladb:
test: add test for group 0 schema versioning
test/pylib: log_browsing: fix type hint
feature_service: enable `GROUP0_SCHEMA_VERSIONING` in Raft mode
schema_tables: don't delete `version` cell from `scylla_tables` mutations from group 0
migration_manager: add `committed_by_group0` flag to `system.scylla_tables` mutations
schema_tables: use schema version from group 0 if present
migration_manager: store `group0_schema_version` in `scylla_local` during schema changes
migration_manager: migration_request handler: assume `canonical_mutation` support
system_keyspace: make `get/set_scylla_local_param` public
feature_service: add `GROUP0_SCHEMA_VERSIONING` feature
schema_tables: refactor `scylla_tables(schema_features)`
migration_manager: add `std::move` to avoid a copy
schema_tables: remove default value for `reload` in `merge_schema`
schema_tables: pass `reload` flag when calling `merge_schema` cross-shard
system_keyspace: fix outdated comment
when compiling the tests with -Wsign-compare, the compiler complains like:
```
/home/kefu/.local/bin/clang++ -DBOOST_ALL_DYN_LINK -DBOOST_NO_CXX98_FUNCTION_BASE -DDEBUG -DDEBUG_LSA_SANITIZER -DFMT_DEPRECATED_OSTREAM -DFMT_SHARED -DSANITIZE -DSCYLLA_BUILD_MODE=debug -DSCYLLA_ENABLE_ERROR_INJECTION -DSEASTAR_API_LEVEL=7 -DSEASTAR_BROKEN_SOURCE_LOCATION -DSEASTAR_DEBUG -DSEASTAR_DEBUG_SHARED_PTR -DSEASTAR_DEFAULT_ALLOCATOR -DSEASTAR_LOGGER_TYPE_STDOUT -DSEASTAR_SCHEDULING_GROUPS_COUNT=16 -DSEASTAR_SHUFFLE_TASK_QUEUE -DSEASTAR_TESTING_MAIN -DSEASTAR_TYPE_ERASE_MORE -DXXH_PRIVATE_API -I/home/kefu/dev/scylladb -I/home/kefu/dev/scylladb/build/cmake/gen -I/home/kefu/dev/scylladb/seastar/include -I/home/kefu/dev/scylladb/build/cmake/seastar/gen/include -isystem /home/kefu/dev/scylladb/build/cmake/rust -Wall -Werror -Wextra -Wno-error=deprecated-declarations -Wimplicit-fallthrough -Wno-c++11-narrowing -Wno-mismatched-tags -Wno-overloaded-virtual -Wno-unsupported-friend -Wno-unused-parameter -Wno-missing-field-initializers -Wno-deprecated-copy -Wno-ignored-qualifiers -march=westmere -Og -g -gz -std=gnu++20 -fvisibility=hidden -U_FORTIFY_SOURCE -DSEASTAR_SSTRING -Wno-error=unused-result "-Wno-error=#warnings" -fstack-clash-protection -fsanitize=address -fsanitize=undefined -fno-sanitize=vptr -MD -MT test/boost/CMakeFiles/tablets_test.dir/tablets_test.cc.o -MF test/boost/CMakeFiles/tablets_test.dir/tablets_test.cc.o.d -o test/boost/CMakeFiles/tablets_test.dir/tablets_test.cc.o -c /home/kefu/dev/scylladb/test/boost/tablets_test.cc
/home/kefu/dev/scylladb/test/boost/tablets_test.cc:1335:53: error: comparison of integers of different signs: 'int' and 'size_t' (aka 'unsigned long') [-Werror,-Wsign-compare]
for (int log2_tablets = 0; log2_tablets < tablet_count_bits; ++log2_tablets) {
~~~~~~~~~~~~ ^ ~~~~~~~~~~~~~~~~~
```
in this case, it should be safe to use an signed int as the loop
variable to be compared with `tablet_count_bits`, but let's just
appease the compiler so we can enable the warning option project-wide
to prevent any potential issues caused by signed-unsigned comparision.
Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
Closesscylladb/scylladb#15449
As promised in earlier commits:
Fixes: #7620Fixes: #13957
Also modify two test cases in `schema_change_test` which depend on
the digest calculation method in their checks. Details are explained in
the comments.
Load balancer will recognize decommissioning nodes and will
move tablet replicas away from such nodes with highest priority.
Topology changes have now an extra step called "tablet draining" which
calls the load balancer. The step will execute tablet migration track
as long as there are nodes which require draining. It will not do regular
load balancing.
If load balancer is unable to find new tablet replicas, because RF
cannot be met or availability is at risk due to insufficient node
distribution in racks, it will throw an exception. Currently, topology
change will retry in a loop. We should make this error cause topology
change to be aborted. There is no infrastructure for
aborts yet, so this is not implemented.
Closes#15197
* github.com:scylladb/scylladb:
tablets, raft topology: Add support for decommission with tablets
tablet_allocator: Compute load sketch lazily
tablet_allocator: Set node id correctly
tablet_allocator: Make migration_plan a class
tablets: Implement cleanup step
storage_service, tablets: Prevent stale RPCs from running beyond their stage
locator: Introduce tablet_metadata_guard
locator, replica: Add a way to wait for table's effective_replication_map change
storage_service, tablets: Extract do_tablet_operation() from stream_tablet()
raft topology: Add break in the final case clause
raft topology: Fix SIGSEGV when trace-level logging is enabled
raft topology: Set node state in topology
raft topology: Always set host id in topology
Load balancer will recognize decommissioning nodes and will
move tablet replicas away from such nodes with highest priority.
Topology changes have now an extra step called "tablet draining" which
calls the load balancer. The step will execute tablet migration track
as long as there are nodes which require draining. It will not do regular
load balancing.
If load balancer is unable to find new tablet replicas, because RF
cannot be met or availability is at risk due to insufficient node
distribution in racks, it will throw an exception. Currently, topology
change will retry in a loop. We should make this error cause topology
change to be paused so that admin becomes aware of the problem and
issues an abort on the topology change. There is no infrastructure for
aborts yet, so this is not implemented.
