d33bb6ea00
Fix the persistent flakiness in `test_incremental_repair_race_window_promotes_unrepaired_data` (SCYLLADB-1478, reopened). After restarting servers[1], the topology coordinator can initiate a **residual re-repair** when it sees tablets stuck in the `repair` stage. This re-repair flushes memtables on all replicas and marks post-repair data as repaired, contaminating the test state and masking the compaction-merge bug the test is designed to detect. The assertion then fails on the *next* retry because the previous attempt's re-repair left behind repaired sstables containing post-repair keys. 1. **Propagating `current_key` through the exception** — correctly advanced the key counter on retry, but the contaminated tablet metadata from the prior re-repair (repaired sstables with post-repair keys) was still present, causing assertion failures on the next attempt. 2. **DROP TABLE + CREATE TABLE between retries** — the tablet metadata (sstables_repaired_at, repair stage) is tied to the tablet identity, and recreating the table in the same keyspace still showed residual state issues. Instead of trying to clean up contaminated state, each retry creates a **completely fresh keyspace** (unique name via `create_new_test_keyspace`). This gives entirely new tablets with no residual repair metadata from prior attempts. Combined with broader detection of coordinator changes and residual re-repairs, the test reliably retries before any contamination can cause false failures. The detection is now comprehensive: - **Broadened coordinator check**: any coordinator change (`new_coord != coord`), not just migration to servers[1] - **Re-repair detection** at three points: post-restart, during the compaction poll, and after injection release — grep for `"Initiating tablet repair host="` in the coordinator log 1. **`test: extract _setup_table_for_race_window helper`** — pure code-movement refactor that extracts keyspace+table+data+repair1+data+flush into a reusable helper. Easily verifiable as a no-op behavioral change. 2. **`test: fix race window test flakiness from residual re-repair`** — the actual fix: broadened detection logic + re-repair grep at 3 points + fresh-keyspace retry on exception. Passed 1000 consecutive runs with the fix applied. Without the fix, about 2% flakiness was observed in debug mode. Fixes: SCYLLADB-1478 So far, we haven't observed flakiness of this test on branches, so not backporting yet. Will backport if seen. Closes scylladb/scylladb#29721 * github.com:scylladb/scylladb: test: fix race window test flakiness from residual re-repair test: extract _setup_table_for_race_window helper for race window test
Scylla
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:
- Developer documentation for more information on building Scylla.
- Build documentation on how to build Scylla binaries, tests, and packages.
- Docker image build documentation for information on how to build Docker images.
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
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.