c59985c38b
Queries are stored and passed around as sstring/std::string_view. While normally they are small enough to not cause problems, as the `test_cdc_large_values.TestLargeColumnsWithCDC.test_single_column_blob_max_size_with_cdc_preimage_full_postimage[unprepared_statements]` demonstrates, queries can be arbitrarily large, putting heavy strain on Scylla internals via large allocations, in the extreme case causing denial of service. This PR attempts to alleviate this by using fragmented storage for queries: read query as fragmented string from the input stream in `transport/server.cc`, propagate it as such to `query_processor::prepare()` and also store it as such in `cql3::cql_statement::raw_cql_statement`. Also avoid linearizing raw values during in the CQL expression tree: switch `cql3::expr::untyped_constant::raw_text` to fragmented storage. For this to be possible, some infrastructure code had to be made fragmented storage friendly: ascii/utf8 validation, hashers, from_hex and importantly: `abstract_type::from_string()`. Unfortunately, the query still has to be linearized for parsing itself, as ANTLR -- although allows for custom InputStream implementation -- plays pointer arithmetics games with the pointers obtained from them, so fragmented input cannot be used. Still, this PR limits the places where the query is linearized to the following: * Parsing * Audit * Logs and error messages So the normal query paths for queries that actually can get arbitrarily large (UPDATE and INSERT) should only linearize the query temporarily for parsing. Fixes #10779 Improvement, no backport Closes scylladb/scylladb#28619 * github.com:scylladb/scylladb: tracing: add_query(): change query param to utils::chunked_string cql3: store raw query string in utils::chunked_string serializer: add serializer<utils::chunked_string> utils/reusable_buffer: add get_linearized_view(managed_bytes_view) cql3/expr: use utils::chunked_string for untyped_constant::raw_text types: abstract_type::from_string() switch to fragmented buffers (implementation) types: abstract_type::from_string() switch to fragmented buffers (interface) types: use write_fragmented from utils/fragment_range.hh types: timestamp_from_string(): don't assume std::string_view is null-terminated types/duration: don't assume std::string_view is null-terminated utils/hashers: add calculate(managed_bytes_view) overload utils/ascii: add validate(managed_bytes_view) overload utils: add managed_bytes_fwd.hh utils: add chunked_string utils: add managed_bytes_basic_view::byte_iterator
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.