d38f44208a
Several tests in test_select_from_mutation_fragments.py assume that all mutations end up in a single SSTable. This assumption can be violated by background memtable flushes triggered by commitlog disk pressure. Since the Scylla node is taken from a pool, it may carry unflushed data from prior tests that prevents closed segments from being recycled, thereby increasing the commitlog disk usage. A main source of such pressure is keyspace-level flushes from earlier tests in this module, which rotate commitlog segments without flushing system tables (e.g., `system.compaction_history`), leaving closed segments dirty. Additionally, prior tests in the same module may have left unflushed data on the shared test table (`test_table` fixture), keeping commitlog segments dirty on its behalf as well. When commitlog disk usage exceeds its threshold, the system flushes the test table to reclaim those segments, potentially splitting a running test's mutations across multiple SSTables. This was observed in CI, where test_paging failed because its data was split across two SSTables, resulting in more mutation fragments than the hardcoded expected count. This patch fixes the affected tests in two ways: 1. Where possible, tests are reworked to not assume a single SSTable: - test_paging - test_slicing_rows - test_many_partition_scan 2. Where rework is impractical, major compaction is added after writes and before validation to ensure that only one SSTable will exist: - test_smoke - test_count - test_metadata_and_value - test_slicing_range_tombstone_changes Fixes SCYLLADB-1375. Signed-off-by: Nikos Dragazis <nikolaos.dragazis@scylladb.com> Closes scylladb/scylladb#29389
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.