247b84715a
Recently, some users have seen "Key size too large" errors in various places. Cassandra and Scylla impose a 64KB length limit on keys, and we have known about bugs in this area for a long time - and even had some translated Cassandra unit tests that cover some of them. But these tests did not cover all the corner cases and left us with partial and fragmented knowledge of this problem, spread over many test files and many issues. In this patch, we add a single test file, test/cql-pytest/test_key_length.py which attempts to rigourously explore the various bugs we have with CQL key length limits. These test aim to reproduce all known bugs in this area: * Refs #3017 - CQL layer accepts set values too large to be written to an sstable * Refs #10366 - Enforce Key-length limits during SELECT * Refs #12247 - Better error reporting for oversized keys during INSERT * Refs #16772 - Key length should be limited to exactly 65535, not less The following less interesting bug is already covered by many tests so I decided not to test it again: * Refs #7745 - Length of map keys and set items are incorrectly limited to 64K in unprepared CQL There's also a situation in materialized views and secondary indexes, where a column that was _not_ a key, now becomes a key, and a length limit needs to be enforced on it. We already have good test coverage for this (in test/cql-pytest/test_secondary_index.py and in test/cql-pytest/test_materialized_view.py), and we have an issue: * Refs #8627 - Cleanly reject updates with indexed values where value > 64k All 16 tests added here pass on Cassandra 5 except one that fails on https://issues.apache.org/jira/browse/CASSANDRA-19270, but 11 of the tests currently fail on Scylla (6 on #12247, 2 on #10366, 3 on #16772). It is possible that our decision in #16772 will not be to fix Scylla to match Cassandra but rather to declare that strict compatibility isn't needed in this case or even that Cassandra is wrong. But even then, having these tests which demonstrate the behavior of both Cassandra and Scylla will be important. Signed-off-by: Nadav Har'El <nyh@scylladb.com> Closes scylladb/scylladb#16779
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++20 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 the ScyllaDB open source.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.