4d99cd2055
Add the gossip state for broadcasting the nodes state_id. Implemented the Group0 state broadcaster (based on the gossip) that will broadcast the state id of each node and check the minimal state id for the tombstone GC. When there is a change in the tombstone GC minimal state id, the state broadcaster will update the tombstone GC time for the group0-managed tables. The main component of the change is the newly added `group0_state_id_handler` that keeps track, broadcasts and receives the last group0 state_ids across all nodes and sets the tombstone GC deletion time accordingly: * on each group0 change applied, the state_id handler broadcasts the state_id as a gossip state (only if the value has changed) * the handler checks for the node state ids every refresh period (configurable, 1h by default) * on every check, the handler figures out the lowest state_id (timeuuid), which is state_id that all of the nodes already have * the timestamp of this minimum state_id is then used to set the tombstone GC deletion time * the tombstone GC calculation then uses that deletion time to provide the GC time back to the callers, e.g. when doing the compaction * (as the time for tombstone GC calculation has the 1s granularity we actually deduce 1s from the determined timestamp, because it can happen that there were some newer mutations received in the same second that were not distributed across the nodes yet) This change introduces a new flag to the static schema descriptor (`is_group0_table`) that is being checked for this newly added mode in the tombstone GC. We also add a check (in non-release builds only) on every group0 modification that the table has this flag set. The group0 tombstone GC handling is similar to the "repair" tombstone GC mode in a sense (that the tombstone GC time is determined according to a reconciliation action), however it is not explicitly visible to (nor editable by) the user. And also the tombstone GC calculation is much simpler than the "repair" mode calculation - for example, we always use the whole range (as opposed to the "repair" mode that can have specific repair times set for specific ranges). We use the group0 configuration to determine the set of nodes (both current and previous in case of joint configuration) - we need to make sure that we account for all the group0 nodes (if any node didn't provide the state_id yet, the current check round will be skipped, i.e. no GC will be done until all known nodes provide their state_id timestamp value). Also note that the group0 state_id handling works on all nodes independently, i.e. each node might have its own (possibly different) state depending on the gossip application state propagation. This is however not a problem, as some nodes might be behind, but they will catch up eventually, and this solution has the benefit of being distributed (as opposed to having a central point to handle the state, like for example the topology coordinator that has been considered in the early stages of the design). Fixes: scylladb/scylla#15607 New feature, should not be backported. Closes scylladb/scylladb#20394 * github.com:scylladb/scylladb: raft: add the check for the group0 tables raft: fast tombstone GC for group0-managed tables tombstone_gc: refactor the repair map raft: flag the group0-managed tables gossip: broadcast the group0 state id raft/test: add test for the group0 tombstone GC treewide: code cleanup and refactoring
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 the ScyllaDB open source.
- The developers mailing list is for developers and people interested in following the development of ScyllaDB to discuss technical topics.