c8ee7d4499
Using consistent cluster management and not using schema commitlog ends with a bad configuration throw during bootstrap. Soon, we will make consistent cluster management mandatory. This forces us to also make schema commitlog mandatory, which we do in this patch. A booting node decides to use schema commitlog if at least one of the two statements below is true: - the node has `force_schema_commitlog=true` config, - the node knows that the cluster supports the `SCHEMA_COMMITLOG` cluster feature. The `SCHEMA_COMMITLOG` cluster feature has been added in version 5.1. This patch is supposed to be a part of version 6.0. We don't support a direct upgrade from 5.1 to 6.0 because it skips two versions - 5.2 and 5.4. So, in a supported upgrade we can assume that the version which we upgrade from has schema commitlog. This means that we don't need to check the `SCHEMA_COMMITLOG` feature during an upgrade. The reasoning above also applies to Scylla Enterprise. Version 2024.2 will be based on 6.0. Probably, we will only support an upgrade to 2024.2 from 2024.1, which is based on 5.4. But even if we support an upgrade from 2023.x, this patch won't break anything because 2023.1 is based on 5.2, which has schema commitlog. Upgrades from 2022.x definitely won't be supported. When we populate a new cluster, we can use the `force_schema_commitlog=true` config to use schema commitlog unconditionally. Then, the cluster feature check is irrelevant. This check could fail because we initiate schema commitlog before we learn about the features. The `force_schema_commitlog=true` config is especially useful when we want to use consistent cluster management. Failing feature checks would lead to crashes during initial bootstraps. Moreover, there is no point in creating a new cluster with `consistent_cluster_management=true` and `force_schema_commitlog=false`. It would just cause some initial bootstraps to fail, and after successful restarts, the result would be the same as if we used `force_schema_commitlog=true` from the start. In conclusion, we can unconditionally use schema commitlog without any checks in 6.0 because we can always safely upgrade a cluster and start a new cluster. Apart from making schema commitlog mandatory, this patch adds two changes that are its consequences: - making the unneeded `force_schema_commitlog` config unused, - deprecating the `SCHEMA_COMMITLOG` feature, which is always assumed to be true. Closes scylladb/scylladb#16254
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.