Avi Kivity d4c28ee317 Merge 'service_levels: mark v2 migration complete on empty legacy table' from Alex Dathskovsky
During raft-topology upgrade in 2026.1, service_level_controller::migrate_to_v2() returns early when system_distributed.service_levels is empty. This skips the service_level_version = 2 write, so the cluster is never marked as upgraded to service levels v2 even though there is no data to migrate. Subsequent upgrades may then fail the startup check which requires service_level_version == 2.
Remove the early return and let the migration commit the version marker even when there are no legacy service levels rows to copy.

Fixes: https://scylladb.atlassian.net/browse/SCYLLADB-1198

backport: should be backported to all versions that can be upgraded to 2026.2

Closes scylladb/scylladb#29333

* github.com:scylladb/scylladb:
  test/auth_cluster: cover empty legacy table in service level upgrade
  service_levels: mark v2 migration complete on empty legacy table

(cherry picked from commit 95e422db48)

Closes scylladb/scylladb#29352
2026-04-06 17:51:34 +03:00
2026-04-01 04:35:14 +03:00
2025-08-22 09:49:52 +03:00
2025-08-19 13:09:18 +03:00
2025-07-08 10:38:23 +03:00

Scylla

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What is Scylla?

Scylla is the real-time big data database that is API-compatible with Apache Cassandra and Amazon DynamoDB. Scylla embraces a shared-nothing approach that increases throughput and storage capacity to realize order-of-magnitude performance improvements and reduce hardware costs.

For more information, please see the ScyllaDB web site.

Build Prerequisites

Scylla is fairly fussy about its build environment, requiring very recent versions of the C++23 compiler and of many libraries to build. The document HACKING.md includes detailed information on building and developing Scylla, but to get Scylla building quickly on (almost) any build machine, Scylla offers a frozen toolchain, This is a pre-configured Docker image which includes recent versions of all the required compilers, libraries and build tools. Using the frozen toolchain allows you to avoid changing anything in your build machine to meet Scylla's requirements - you just need to meet the frozen toolchain's prerequisites (mostly, Docker or Podman being available).

Building Scylla

Building Scylla with the frozen toolchain dbuild is as easy as:

$ git submodule update --init --force --recursive
$ ./tools/toolchain/dbuild ./configure.py
$ ./tools/toolchain/dbuild ninja build/release/scylla

For further information, please see:

Running Scylla

To start Scylla server, run:

$ ./tools/toolchain/dbuild ./build/release/scylla --workdir tmp --smp 1 --developer-mode 1

This will start a Scylla node with one CPU core allocated to it and data files stored in the tmp directory. The --developer-mode is needed to disable the various checks Scylla performs at startup to ensure the machine is configured for maximum performance (not relevant on development workstations). Please note that you need to run Scylla with dbuild if you built it with the frozen toolchain.

For more run options, run:

$ ./tools/toolchain/dbuild ./build/release/scylla --help

Testing

Build with the latest Seastar Check Reproducible Build clang-nightly

See test.py manual.

Scylla APIs and compatibility

By default, Scylla is compatible with Apache Cassandra and its API - CQL. There is also support for the API of Amazon DynamoDB™, which needs to be enabled and configured in order to be used. For more information on how to enable the DynamoDB™ API in Scylla, and the current compatibility of this feature as well as Scylla-specific extensions, see Alternator and Getting started with Alternator.

Documentation

Documentation can be found here. Seastar documentation can be found here. User documentation can be found here.

Training

Training material and online courses can be found at Scylla University. The courses are free, self-paced and include hands-on examples. They cover a variety of topics including Scylla data modeling, administration, architecture, basic NoSQL concepts, using drivers for application development, Scylla setup, failover, compactions, multi-datacenters and how Scylla integrates with third-party applications.

Contributing to Scylla

If you want to report a bug or submit a pull request or a patch, please read the contribution guidelines.

If you are a developer working on Scylla, please read the developer guidelines.

Contact

  • The community forum and Slack channel are for users to discuss configuration, management, and operations of ScyllaDB.
  • The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.
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