081f30d149
Support for splitting tablet storage is added. Until now, tablet storage was composed of a single compaction group, i.e. a group of sstables eligible to be compacted together. For splitting, tablet storage can now be composed of multiple compaction groups, main, left and right. Main group stores sstables that require splitting, whereas left and right groups store sstables that were already split according to the tablet's token range. After table storage is put in splitting mode, new writes will only go to either left or right group, depending on the token. When all main groups completed splitting their sstables, then coordinator can proceed with tablet metadata changes. The coordination part is not implemented yet. Only the storage part. The former will come next and will be wired into the latter. Missing: - splitting monitor (verify whether coordinator asked for splitting and acts accordingly) (will come next) Closes scylladb/scylladb#16158 * github.com:scylladb/scylladb: replica: Introduce storage group splitting replica: Add storage_group::memtable_count() replica: Add compaction_group::empty() replica: Rename compaction_group_manager to storage_group_manager replica: Introduce concept of storage group compaction: Add splitting compaction task to manager compaction: Prepare rewrite_sstables_compaction_task_executor to be reused for splitting compaction: remove scrub-specific code from rewrite_sstables_compaction_task_executor replica: Allow uncompacted SSTables to be moved into a new set compaction: Add splitting compaction flat_mutation_reader: Allow interposer consumers to be stacked mutation_writer: Introduce token-group-based mutation segregator locator: Introduce tablet_map::get_tablet_id_and_range_side(token)
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 APIs - CQL and Thrift. 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.