f5886b4fdd
This PR exposes vnodes-to-tablets migrations through the task manager API via a virtual task. This allows users to list, query status, and wait on ongoing migrations through a standard interface, consistent with other global operations such as tablet operations and topology requests are already exposed. The virtual task exposes all migrations that are currently in progress. Each migrating keyspace appears as a separate task, identified by a deterministic name-based (v3) UUID derived from the keyspace name. Progress is reported as the number of nodes that have switched to tablets vs. the total. The number increases on the forward path and decreases on rollback. The task is not abortable - rolling back a migration requires a manual procedure. The `wait` API blocks until the migration either completes (returning `done`) or is rolled back (returning `suspended`). Example output: ``` $ scylla nodetool tasks list vnodes_to_tablets_migration task_id type kind scope state sequence_number keyspace table entity shard start_time end_time 1747b573-6cd6-312d-abb1-9b66c1c2d81f vnodes_to_tablets_migration cluster keyspace running 0 ks 0 $ scylla nodetool tasks status 1747b573-6cd6-312d-abb1-9b66c1c2d81f id: 1747b573-6cd6-312d-abb1-9b66c1c2d81f type: vnodes_to_tablets_migration kind: cluster scope: keyspace state: running is_abortable: false start_time: end_time: error: parent_id: none sequence_number: 0 shard: 0 keyspace: ks table: entity: progress_units: nodes progress_total: 3 progress_completed: 0 ``` Fixes SCYLLADB-1150. New feature, no backport needed. Closes scylladb/scylladb#29256 * github.com:scylladb/scylladb: test: cluster: Verify vnodes-to-tablets migration virtual task distributed_loader: Link resharding tasks to migration virtual task distributed_loader: Make table_populator aware of migration rollbacks service: Add virtual task for vnodes-to-tablets migrations storage_service: Guard migration status against uninitialized group0 compaction: Add parent_id to table_resharding_compaction_task_impl storage_service: Add keyspace-level migration status function storage_service: Replace migration status string with enum utils: Add UUID::is_name_based()
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++23 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 API - CQL. 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 ScyllaDB.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.