44c605e59c
This patch increases the compatibility with DynamoDB Streams by integrating the DynamoDB's event type rules (described in https://github.com/scylladb/scylladb/issues/6918) into Alternator. The main changes are: - introduce a new flag `alternator_streams_strict_compatibility`, meant as a guard of performance-intensive operations that increase the compatibility with DynamoDB Streams. If enabled, Alternator always performs a RBW before a data-modifying operation, and propagates its result to CDC. Then, the old item is compared to the new one, to determine the mutation type (INSERT vs MODIFY). This option is a no-op for tables with disabled Alternator Streams, - reduce splitting of simple Alternator mutations, - correctly distinguish event types described in #6918, except for item deletes. Deleting a missing item with DeleteItem, BatchWriteItem, or a missing field with UpdateItem still emit REMOVEs. To summarize, the emitted events of the data manipulation operations should be as follows: - DeleteItem/BatchWriteItem.DeleteItem of existing item: REMOVE (OK) - DeleteItem of nonexistent item: nothing (OK) - BatchWriteItem.DeleteItem of nonexistent item: nothing (OK) - PutItem/UpdateItem/BatchWriteItem.PutItem of existing and not equal item: MODIFY (OK) - PutItem/UpdateItem/BatchWriteItem.PutItem of existing and equal item: nothing (OK) - PutItem/UpdateItem/BatchWriteItem.PutItem of nonexistent item: INSERT (OK) No backport is necessary. Refs https://github.com/scylladb/scylladb/pull/26149 Refs https://github.com/scylladb/scylladb/pull/26396 Refs https://github.com/scylladb/scylladb/issues/26382 Fixes https://github.com/scylladb/scylladb/issues/6918 Closes scylladb/scylladb#26121 * github.com:scylladb/scylladb: test/alternator: Enable the tests failing because of #6918 alternator, cdc: Don't emit events for no-op removes alternator, cdc: Don't emit an event for equal items alternator/streams, cdc: Differentiate item replace and item update in CDC alternator: Change the return type of rmw_operation_return config: Add alternator_streams_strict_compatibility flag cdc: Don't split a row marker away from row cells
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.