9edf0709e6
In this commit we enhance token_metadata with a pointer to the new host_id-based generic_token_metadata specialisation (token_metadata2). The idea is that in the following commits we'll go over all token_metadata modifications and make the corresponding modifications to its new host_id-based alternative. The pointer to token_metadata2 is stored in the generic_token_metadata::_new_value field. The pointer can be mutable, immutable, or absent altogether (std::monostate). It's mutable if this generic_token_metadata owns it, meaning it was created using the generic_token_metadata(config cfg) constructor. It's immutable if the generic_token_metadata(lw_shared_ptr<const token_metadata2> new_value); constructor was used. This means this old token_metadata is a wrapper for new token_metadata and we can only use the get_new() method on it. The field _new_value is empty for the new host_id-based token_metadata version. The generic_token_metadata(std::unique_ptr<token_metadata_impl<NodeId>> impl, token_metadata2 new_value); constructor is used for clone methods. We clone both versions, and we need to pass a cloned token_metadata2 into constructor. There are two overloads of get_new, for mutable and immutable generic_token_metadata. Both of them throws an exception if they can't get the appropriate pointer. There is also a get_new_strong method, which returns an immutable owning pointer. This is convenient since a lot of API's want an owning pointer. We can't make the get_new/get_new_strong API simpler and use get_new_strong everywhere since it mutate the original generic_token_metadata by incrementing the reference counter and this causes raises when it's passed between shards in replicate_to_all_cores.
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.