1007ac4956
Before the patch we called `gossiper.remove_endpoint` for IP-s of the left nodes. The problem is that in replace-with-same-ip scenario we called `gossiper.remove_endpoint` for IP which is used by the new, replacing node. The `gossiper.remove_endpoint` method puts the IP into quarantine, which means gossiper will ignore all events about this IP for `quarantine_delay` (one minute by default). If we immediately replace just replaced node with the same IP again, the bootstrap will fail since the gossiper events are blocked for this IP, and we won't be able to resolve an IP for the new host_id. Another problem was that we called gossiper.remove_endpoint method, which doesn't remove an endpoint from `_endpoint_state_map`, only from live and unreachable lists. This means the IP will keep circulating in the gossiper message exchange between cluster nodes until full cluster restart. This patch fixes both of these problems. First, we rely on the fact that when topology coordinator moves the `being_replaced` node to the left state, the IP of the `replacing` node is known to all nodes. This means before removing an IP from the gossiper we can check if this IP is currently used by another node in the current raft topology. This is done by constructing the `used_ips` map based on normal and transition nodes. This map is cached to avoid quadratic behaviour. Second, we call `gossiper.force_remove_endpoint`, not `gossiper.remove_endpoint`. This function removes and IP from `_endpoint_state_map`, as well as from live and unreachable lists. Closes scylladb/scylladb#16820 * github.com:scylladb/scylladb: get_peer_info_for_update: update only required fields in raft topology mode get_peer_info_for_update: introduce set_field lambda storage_service::on_change: fix indent storage_service::on_change: skip handle_state functions in raft topology mode test_replace_different_ip: check old IP is removed from gossiper test_replace: check two replace with same IP one after another storage_service: sync_raft_topology_nodes: force_remove_endpoint for left nodes only if an IP is not used by other nodes
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.