1545ae2d3b
Today, SSTable cleanup skips to the next partition, one at a time, when it finds that the current partition is no longer owned by this node. That's very inefficient because when a cluster is growing in size, existing nodes lose multiple sequential tokens in its owned ranges. Another inefficiency comes from fetching index pages spanning all unowned tokens, which was described in https://github.com/scylladb/scylladb/issues/14317. To solve both problems, cleanup will now use multi range reader, to guarantee that it will only process the owned data and as a result skip unowned data. This results in cleanup scanning an owned range and then fast forwarding to the next one, until it's done with them all. This reduces significantly the amount of data in the index caching, as index will only be invoked at each range boundary instead. Without further ado, before: `INFO 2023-07-01 07:10:26,281 [shard 0] compaction - [Cleanup keyspace2.standard1 701af580-17f7-11ee-8b85-a479a1a77573] Cleaned 1 sstables to [./tmp/1/keyspace2/standard1-b490ee20179f11ee9134afb16b3e10fd/me-3g7a_0s8o_06uww24drzrroaodpv-big-Data.db:level=0]. 2GB to 1GB (~50% of original) in 26248ms = 81MB/s. ~9443072 total partitions merged to 4750028.` after: `INFO 2023-07-01 07:07:52,354 [shard 0] compaction - [Cleanup keyspace2.standard1 199dff90-17f7-11ee-b592-b4f5d81717b9] Cleaned 1 sstables to [./tmp/1/keyspace2/standard1-b490ee20179f11ee9134afb16b3e10fd/me-3g7a_0s4m_5hehd2rejj8w15d2nt-big-Data.db:level=0]. 2GB to 1GB (~50% of original) in 17424ms = 123MB/s. ~9443072 total partitions merged to 4750028.` Fixes #12998. Fixes #14317. Closes #14469 * github.com:scylladb/scylladb: test: Extend cleanup correctness test to cover more cases compaction: Make SSTable cleanup more efficient by fast forwarding to next owned range sstables: Close SSTable reader if index exhaustion is detected in fast forward call sstables: Simplify sstable reader initialization compaction: Extend make_sstable_reader() interface to work with mutation_source test: Extend sstable partition skipping test to cover fast forward using 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.