bb81dbf65e
Adds write-path guardrails that reject or warn on mutations targeting partitions, rows, or collections that already exceed configured size thresholds, based on SSTable `large_data_record` metadata. ScyllaDB already detects and records large partitions/rows/cells in `system.large_data_records` after compaction, but takes no preventive action on the write path. Once a partition grows past operational limits it causes latency spikes, OOM, and repair failures. These guardrails let operators set hard and soft thresholds so that writes to already-oversized data are rejected (hard) or logged as warnings (soft) before they make the problem worse. - **Intrusive index over SSTable metadata**: A per-table `large_data_record_index` maintains three `boost::intrusive::multiset`s (partitions, rows, cells) using `auto_unlink` hooks directly on `large_data_record`. SSTable destruction automatically removes records from the index — no explicit deregistration needed. - **Virtual dispatch for zero-cost disabled path**: `large_data_guardrail_base` → `noop_large_data_guardrail` / `large_data_guardrail`. Tables without guardrails enabled pay only a virtual call to a no-op. No index is built or maintained for disabled tables. - **Schema storage**: The per-table flag is stored as a scylla_tables column, following the tablets pattern: only write a live cell when enabled, omit entirely when disabled. The CQL feature gate prevents enabling until all nodes are upgraded. - **Write-path integration**: The guardrail check runs in `do_apply` after the frozen mutation is deserialized but before it is applied to the memtable. Hint replay and Paxos learn skip the check via `skip_large_data_guardrails`. Uses existing `large_*_warn_threshold` config options as soft limits and new `large_*_fail_threshold` options as hard limits. Checked dimensions: - Partition size (bytes) - Partition row count - Row size (bytes) - Collection element count Backport is not required Fixes https://scylladb.atlassian.net/browse/SCYLLADB-180 Closes scylladb/scylladb#29733 * github.com:scylladb/scylladb: test/cqlpy: add per-table toggle, LWT exemption, and multi-category tests test/cqlpy: add large collection guardrail tests test/cqlpy: add large row guardrail tests test/cqlpy: add large partition guardrail tests test/boost: add large_data_guardrail unit tests test/cluster: add large data guardrails rolling upgrade test replica: wire large_data_guardrail into the write path schema: add per-table large_data_guardrails_enabled flag db: implement large_data_guardrail db: implement large_data_record_index sstables: add intrusive index hook to large_data_record db: add large_collection_elements_fail_threshold config option db: add large_row_fail_threshold_mb config option db: add rows_count_fail_threshold config option db: add large_partition_fail_threshold_mb config option replica: introduce large_data_exception
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.