98139a8716
PR #17771 introduced a threshold for the total memory used by all bloom filters across SSTables. When the total usage surpasses the threshold, the largest bloom filter will be removed from memory, bringing the total usage back under the threshold. This PR adds support for reloading such reclaimed bloom filters back into memory when memory becomes available (i.e., within the 10% of available memory earmarked for the reclaimable components). The SSTables manager now maintains a list of all SSTables whose bloom filter was removed from memory and attempts to reload them when an SSTable, whose bloom filter is still in memory, gets deleted. The manager reloads from the smallest to the largest bloom filter to maximize the number of filters being reloaded into memory. Backported from https://github.com/scylladb/scylladb/pull/18186 to 5.4. Closes scylladb/scylladb#18660 * github.com:scylladb/scylladb: sstable_datafile_test: add testcase to test reclaim during reload sstable_datafile_test: add test to verify auto reload of reclaimed components sstables_manager: reload previously reclaimed components when memory is available sstables_manager: start a fiber to reload components sstable_directory_test: fix generation in sstable_directory_test_table_scan_incomplete_sstables sstable_datafile_test: add test to verify reclaimed components reload sstables: support reloading reclaimed components sstables_manager: add new intrusive set to track the reclaimed sstables sstable: add link and comparator class to support new instrusive set sstable: renamed intrusive list link type sstable: track memory reclaimed from components per sstable sstable: rename local variable in sstable::total_reclaimable_memory_size
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.