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For correctness sstable cleanup has to run between (some) topology changes. Sometimes even a failed topology change may require running the cleanup. The series introduces automatic sstable cleanup step to the topology change coordinator. Unlike other operations it is not represented as a global transition state, but done by each node independently which allows cleanup to run without locking the topology state machine so tablet code can run in parallel with the cleanup. It is done by having a cleanup state flag for each node in the topology. The flag is a tri state: "clean" - the node is clean, "needed" - cleanup is needed (but not running), "running" - cleanup is running. No topology operation can proceed if there is a node in "running" state, but some operation can proceed even if there are nodes in "needed" state. If the coordinator needs to perform a topology operation that cannot run while there are nodes that need cleanup the coordinator will start one automatically and continue only after cleanup completes. There is also a possibility to kick cleanup manually through the new RAFT API call. * 'cleanup-needed-v8' of https://github.com/gleb-cloudius/scylla: test: add test for automatic cleanup procedure test: add test for topology requests queue management storage_service: topology coordinator: add error injection point to be able to pause the topology coordinator storage_service: topology coordinator: add logging to removenode and decommission storage_service: topology_coordinator: introduce cleanup REST API integrated with the topology coordinator storage_service: topology coordinator: manage cluster cleanup as part of the topology management storage_service: topology coordinator: provide a version of get_excluded_nodes that does not need node_to_work_on as a parameter test: use servers_see_each_other when needed test: add servers_see_each_other helper storage_service: topology coordinator: make topology coordinator lifecycle subscriber system_keyspace: raft topology: load ignore nodes parameter together with removenode topology request storage_service: topology coordinator: introduce sstable cleanup fiber storage_proxy: allow to wait for all ongoing writes storage_service: topology coordinator: mark nodes as needing cleanup when required storage_service: add mark_nodes_as_cleanup_needed function vnode_effective_replication_map: add get_all_pending_nodes() function vnode_effective_replication_map: pre calculate dirty endpoints during topology change raft topology: add cleanup state to the topology state machine
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.