e8fb718e4a
The patch series introduces linearisable topology changes using raft protocol. The state machine driven by raft is described in "service: Introduce topology state machine". Some explanations about the implementation can be found in "storage_service: raft topology: implement topology management through raft". The code is not ready for production. There is not much in terms of error handling and integration with the rest of the system is not even started. For full integration request fencing will need to be implemented and token_metadata has to be extended to support not just "pending" nodes but concepts of "read replica set" and "write replica set". The code may be far from be usable, but it is hidden behind the "experimental raft" flag and having it in tree will relieve me from constant rebase burden. * 'raft-topology-v6' of github.com:scylladb/scylla-dev: storage_service: fix indentation from previous patch storage_service: raft topology: implement topology management through raft service: raft: make group0_guard move assignable service: raft: wire up apply() and snapshot transfer for topology in group0 state machine storage_service: raft topology: introduce a function that applies topology cmd to local state machine storage_service: raft topology: introduce a raft monitor and topology coordinator fibers storage_service: raft topology: introduce snapshot transfer code for the topology table raft topology: add RAFT_TOPOLOGY_CMD verb that will be used by topology coordinator to communicated with nodes bootstrapper: Add get_random_bootstrap_tokens function service: raft: add support for topology_change command into raft_group0_client service: raft: introduce topology_change group0 command system_keyspace: add a table to persist topology change state machine's state service: Introduce topology state machine data structures storage_proxy: not consult topology on local table write
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.