809ddd7f79
This refactoring is a follow-up for https://github.com/scylladb/scylladb/pull/13376, move per keyspace data structures related to topology changes from `token_metadata` to `erm`. We move `pending_endpoints` and `read_endpoints`, along with their computation logic, from `token_metadata` to `vnode_effective_replication_map`. The `vnode_effective_replication_map` seems more appropriate for them since it contains functionally similar `replication_map` and we will be able to reuse `pending_endpoints/read_endpoints` across keyspaces sharing the same `factory_key`. At present, `pending_endpoints` and `read_endpoints` are updated in the `update_pending_ranges` function. The update logic comprises two parts - preparing data common to all keyspaces/replication_strategies, and calculating the `migration_info` for specific keyspaces. In this PR we introduce a new `topology_change_info` structure to hold the first part's data and create an `update_topology_change_info` function to update it. This structure will be used in `vnode_effective_replication_map` to compute `pending_endpoints` and `read_endpoints`. This enables the reuse of `topology_change_info` across all keyspaces, unlike the current `update_pending_ranges` implementation, which is another benefit of this refactoring. The PR also optimises `replication_map` memory usage for the case `natural_endpoints_depend_on_token == false`. We store endpoints list only once with special key instead of duplicating them for each `vnode` token. The original `update_pending_ranges` remains unchanged during the PR commits, and will be removed entirely upon transitioning to the new implementation. Closes #13715 * github.com:scylladb/scylladb: token_metadata_test: add a test for everywhere strategy token_metadata_test: check read_endpoints when bootstrapping first node token_metadata_test: refactor tests, extract create_erm token_metadata: drop has_pending_ranges and migration_info effective_replication_map: add has_pending_ranges token_metadata: drop update_pending_ranges effective_replication_map: use new get_pending_endpoints and get_endpoints_for_reading token_metadata_test.cc: create token_metadata and replication_strategy as shared pointers vnode_effective_replication_map: get_pending_endpoints and get_endpoints_for_reading calculate_effective_replication_map: compute pending_endpoints and read_endpoints vnode_erm: optimize replication_map vnode_erm::get_range_addresses: use sorted_tokens abstract_replication_strategy.hh: de-virtualize natural_endpoints_depend_on_token sequenced_set: add extract_vector method effective_replication_map: clone_endpoints_gently -> clone_data_gently vnode_erm: gentle destruction of _pending_endpoints and _read_endpoints stall_free.hh: add clear_gently for rvalues stall_free.hh: relax Container requirement token_metadata: add pending_endpoints and read_endpoints to vnode_effective_replication_map token_metadata: introduce topology_change_info token_metadata: replace set_topology_transition_state with set_read_new
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.