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This PR enables **LWT (Lightweight Transactions)** support for tablet-based tables by leveraging **colocated tables**.
Currently, storing Paxos state in system tables causes two major issues:
* **Loss of Paxos state during tablet migration or base table rebuilds**
* When a tablet is migrated or the base table is rebuilt, system tables don't retain Paxos state.
* This breaks LWT correctness in certain scenarios.
* Failing test cases demonstrating this:
* test_lwt_state_is_preserved_on_tablet_migration
* test_lwt_state_is_preserved_on_rebuild
* **Shard misalignment and performance overhead**
* Tablets may be placed on arbitrary shards by the tablet balancer.
* Accessing Paxos state in system tables could require a shard jump, degrading performance.
We move Paxos state into a dedicated Paxos table, colocated with the base table:
* Each base table gets its own Paxos state table.
* This table is lazily created on the first LWT operation.
* Its tablets are colocated with those of the base table, ensuring:
* Co-migration during tablet movement
* Co-rebuilding with the base table
* Shard alignment for local access to Paxos state
Some reasoning for why this is sufficient to preserve LWT correctness is discussed in [2].
This PR addresses two issues from the "Why doesn't it work for tablets" section in [1]:
* Tablet migration vs LWT correctness
* Paxos table sharding
Other issues ("bounce to shard" and "locking for intranode_migration") have already been resolved in previous PRs.
References
[1] - [LWT over tablets design](https://docs.google.com/document/d/1CPm0N9XFUcZ8zILpTkfP5O4EtlwGsXg_TU4-1m7dTuM/edit?tab=t.0#heading=h.goufx7gx24yu)
[2] - [LWT: Paxos state and tablet balancer](https://docs.google.com/document/d/1-xubDo612GGgguc0khCj5ukmMGgLGCLWLIeG6GtHTY4/edit?tab=t.0)
[3] - [Colocated tables PR](https://github.com/scylladb/scylladb/pull/22906#issuecomment-3027123886)
[4] - [Possible LWT consistency violations after a topology change](https://github.com/scylladb/scylladb/issues/5251)
Backport: not needed because this is a new feature.
Closes scylladb/scylladb#24819
* github.com:scylladb/scylladb:
create_keyspace: fix warning for tablets
docs: fix lwt.rst
docs: fix tablets.rst
alternator: enable LWT
random_failures: enable execute_lwt_transaction
test_tablets_lwt: add test_paxos_state_table_permissions
test_tablets_lwt: add test_lwt_for_tablets_is_not_supported_without_raft
test_tablets_lwt: test timeout creating paxos state table
test_tablets_lwt: add test_lwt_concurrent_base_table_recreation
test_tablets_lwt: add test_lwt_state_is_preserved_on_rebuild
test_tablets_lwt: migrate test_lwt_support_with_tablets
test_tablets_lwt: add test_lwt_state_is_preserved_on_tablet_migration
test_tablets_lwt: add simple test for LWT
check_internal_table_permissions: handle Paxos state tables
client_state: extract check_internal_table_permissions
paxos_store: handle base table removal
database: get_base_table_for_tablet_colocation: handle paxos state table
paxos_state: use node_local_only mode to access paxos state
query_options: add node_local_only mode
storage_proxy: handle node_local_only in query
storage_proxy: handle node_local_only in mutate
storage_proxy: introduce node_local_only flag
abstract_replication_strategy: remove unused using
storage_proxy: add coordinator_mutate_options
storage_proxy: rename create_write_response_handler -> make_write_response_handler
storage_proxy: simplify mutate_prepare
paxos_state: lazily create paxos state table
migration_manager: add timeout to start_group0_operation and announce
paxos_store: use non-internal queries
qp: make make_internal_options public
paxos_store: conditional cf_id filter
paxos_store: coroutinize
feature_service: add LWT_WITH_TABLETS feature
paxos_state: inline system_keyspace functions into paxos_store
paxos_state: extract state access functions into paxos_store
Scylla in-source tests.
For details on how to run the tests, see docs/dev/testing.md
Shared C++ utils, libraries are in lib/, for Python - pylib/
alternator - Python tests which connect to a single server and use the DynamoDB API unit, boost, raft - unit tests in C++ cqlpy - Python tests which connect to a single server and use CQL topology* - tests that set up clusters and add/remove nodes cql - approval tests that use CQL and pre-recorded output rest_api - tests for Scylla REST API Port 9000 scylla-gdb - tests for scylla-gdb.py helper script nodetool - tests for C++ implementation of nodetool
If you can use an existing folder, consider adding your test to it. New folders should be used for new large categories/subsystems, or when the test environment is significantly different from some existing suite, e.g. you plan to start scylladb with different configuration, and you intend to add many tests and would like them to reuse an existing Scylla cluster (clusters can be reused for tests within the same folder).
To add a new folder, create a new directory, and then
copy & edit its suite.ini.