fdf61d2f7c
before this change, there are chances that the temporary sstables created for collecting the GC-able data create by a certain compaction can be picked up by another compaction job. this wastes the CPU cycles, adds write amplification, and causes inefficiency. in general, these GC-only SSTables are created with the same run id as those non-GC SSTables, but when a new sstable exhausts input sstable(s), we proactively replace the old main set with a new one so that we can free up the space as soon as possible. so the GC-only SSTables are added to the new main set along with the non-GC SSTables, but since the former have good chance to overlap the latter. these GC-only SSTables are assigned with different run ids. but we fail to register them to the `compaction_manager` when replacing the main sstable set. that's why future compactions pick them up when performing compaction, when the compaction which created them is not yet completed. so, in this change, * to prevent sstables in the transient stage from being picked up by regular compactions, a new interface class is introduced so that the sstable is always added to registration before it is added to sstable set, and removed from registration after it is removed from sstable set. the struct helps to consolidate the regitration related logic in a single place, and helps to make it more obvious that the timespan of an sstable in the registration should cover that in the sstable set. * use a different run_id for the gc sstable run, as it can overlap with the output sstable run. the run_id for the gc sstable run is created only when the gc sstable writer is created. because the gc sstables is not always created for all compactions. please note, all (indirect) callers of `compaction_task_executor::compact_sstables()` passes a non-empty `std::function` to this function, so there is no need to check for empty before calling it. so in this change, the check is dropped. Fixes #14560 Signed-off-by: Kefu Chai <kefu.chai@scylladb.com> Closes #14725
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.