568f20396a
The test_create_index_synchronous_updates test in test_secondary_index_properties.py was intermittently failing with 'assert found_wanted_trace' because the expected trace event 'Forcing ... view update to be synchronous' was missing from the trace events returned by get_query_trace(). Root cause: trace events are written asynchronously to system_traces.events. The Python driver's populate() method considers a trace complete once the session row in system_traces.sessions has duration IS NOT NULL, then reads events exactly once. Since the session row and event rows are written as separate mutations with no transactional guarantee, the driver can read an incomplete set of events. Evidence from the failed CI run logs: - The entire test (CREATE TABLE through DROP TABLE) completed in ~300ms (01:38:54,859 - 01:38:55,157) - The INSERT with tracing happened in a ~50ms window between the second CREATE INDEX completing (01:38:55,108) and DROP TABLE starting (01:38:55,157) - The 'Forcing ... synchronous' trace message is generated during the INSERT write path (db/view/view.cc:2061), so it was produced, but not yet flushed to system_traces.events when the driver read them - This matches the known limitation documented in test/alternator/ test_tracing.py: 'we have no way to know whether the tracing events returned is the entire trace' Fix: replace the single-shot trace.events read with a retry loop that directly queries system_traces.events until the expected event appears (with a 30s timeout). Use ConsistencyLevel.ONE since system_traces has RF=2 and cqlpy tests run on a single-node cluster. The same race condition pattern exists in test_mv_synchronous_updates in test_materialized_view.py (which this test was modeled after), so the same fix is proactively applied there as well. Fixes SCYLLADB-1314 Closes scylladb/scylladb#29374
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.