b39cc01bb3
according to the document "nodetool cleanup" > Triggers removal of data that the node no longer owns currently, scylla performs cleanup by rewriting the sstables. but commitlog segments may still contain the mutations to the tables which are dropped during sstable rewriting. when scylla server restarts, the dirty mutations are replayed to the memtable. if any of these dirty mutations changes the tables cleaned up. the stale data are reapplied. this would lead to data resurrection. so, in this change we following the same model of major compaction: 1. force new active segment, 2. flush all tables 3. perform cleanup using compaction, which rewrites the sstables of specified tables because we already `flush()` all tables in `cleanup_keyspace_compaction_task_impl::run()`, there is no need to call `flush()` again, in `table::perform_cleanup_compaction()`, so the `flush()` call is dropped in this function, and the tests using this function are updated to call `flush()` manually to preserve the existing behavior. there are two callers of `cleanup_keyspace_compaction_task_impl`, * one is `storage_service::sstable_cleanup_fiber()`, which listens for the events fired by topology_state_machine, which is in turn driven by, for instance, "/storage_service/cleanup_all" API. which cleanup all keyspaces in one after another. * another is "/storage_service/keyspace_cleanup", which cleans up the specified keyspace. in the first use case, we can force a new active segment for a single time, so another parameter to the ctor of `cleanup_keyspace_compaction_task_impl` is introduced to specify if the `db.flush_all_tables()` call should be skiped. please note, there are two possible optimizations, 1. force new active segment only if the mutations in it touches the tables being cleaned up 2. after forcing new active segment, only flush the (mem)tables mutated by the non-active segments but let's leave them for following-up changes. this change is a minimal fix for data resurrection issue. Fixes #16757 Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
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.