ffdd47c2b1
Added support to track and limit the memory usage by sstable components. A reclaimable component of an SSTable is one from which memory can be reclaimed. SSTables and their managers now track such reclaimable memory and limit the component memory usage accordingly. A new configuration variable defines the memory reclaim threshold. If the total memory of the reclaimable components exceeds this limit, memory will be reclaimed to keep the usage under the limit. This PR considers only the bloom filters as reclaimable and adds support to track and limit them as required. The feature can be manually verified by doing the following : 1. run a single-node single-shard 1GB cluster 2. create a table with bloom-filter-false-positive-chance of 0.001 (to intentionally cause large bloom filter) 3. populate with tiny partitions 4. watch the bloom filter metrics get capped at 100MB The default value of the `components_memory_reclaim_threshold` config variable which controls the reclamation process is `.1`. This can also be reduced further during manual tests to easily hit the threshold and verify the feature. Fixes #17747 Closes scylladb/scylladb#17771 * github.com:scylladb/scylladb: test_bloom_filter.py: disable reclaiming memory from components sstable_datafile_test: add tests to verify auto reclamation of components test/lib: allow overriding available memory via test_env_config sstables_manager: support reclaiming memory from components sstables_manager: store available memory size sstables_manager: add variable to track component memory usage db/config: add a new variable to limit memory used by table components sstable_datafile_test: add testcase to verify reclamation from sstables sstables: support reclaiming memory from components
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.