284dd21ef7
Rewrite operations are scrub, cleanup and upgrade. Race can happen because 'selection of sstables' and 'mark sstables as compacting' are decoupled. So any deferring point in between can lead to a parallel compaction picking the same files. After commit2cf0c4bbf, files are marked as compacting before rewrite starts, but it didn't take into account the commitc84217adwhich moved retrieval of candidates to a deferring thread, before rewrite_sstables() is even called. Scrub isn't affected by this because it uses a coarse grained approach where whole operation is run with compaction disabled, which isn't good because regular compaction cannot run until its completion. From now on, selection of files and marking them as compacting will be serialized by running them with compaction disabled. Now cleanup will also retrieve sstables with compaction disabled, meaning it will no longer leave uncleaned files behind, which is important to avoid data resurrection if node regains ownership of data in uncleaned files. Fixes #8168. Refs #8155. [backport notes: - minor conflict around run_with_compaction_disabled() - bumped into our old friend https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95111, so I had to use std::ref() on local copy of lambda - with the yielding part of candidate retrieval now happening in rewrite_sstables(), task registration is moved to after run_with_ compaction_disabled() call, so the latter won't incorrectly try to stop the task that called it, which triggers an assert in debug mode. ] Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com> Message-Id: <20211129133107.53011-1-raphaelsc@scylladb.com> (cherry picked from commit80a1ebf0f3) Signed-off-by: Raphael S. Carvalho <raphaelsc@scylladb.com> Closes #10963
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 users mailing list 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.