415c83fa67
before this change, scylla's CMake-based system consumes Seastar library by including it directly. but this failed to address the needs of linking against Seastar shared libraries in Debug and Dev builds, while linking against the static libraries in other builds. because Seastar uses `BUILD_SHARED_LIBS` CMake variable to determine if it builds shared libraries. and we cannot assign different values to this CMake variable based on current configure type -- CMake does not support. see https://gitlab.kitware.com/cmake/cmake/-/issues/19467 in order to address this problem, we have a couple possible solutions: - to enable Seastar to build both shared and static libraries in a pass. without sacrificing the performance, we have to build all object files twice: once with -fPIC, once without. in order to accompolish this goal, we need to develop a machinary to populate the same settings to these two builds. this would complicate the design of Seastar's building system further. - to build Seastar libraries twice in scylla, we could use the ExternalProject module to implement this. but it'd be complicate to extract the compile options, and link options previously populated by Seastar's targets with CMake -- we would have to replicate all of them in scylla. this is out of the question. - to build Seastar libraries twice before building scylla, and let scylla to consume them using CMake config files or .pc files. this is a compromise. it enables scylla to drive the build of Seastar libraries and to consume the compile options and link options. the downside is: * the generated compilation database (compile_commands.json) does not include the commands building Seastar anymore. * the building system of scylla does not have finer graind control on the building process of seastar. for instance, we cannot specify the build dependency to a certain seastar library, and just build it instead of building the whole seastar project. turns out the last approach is the best one we can have at this moment. this is also the approach used by the existing `configure.py`. in this change, we - add FindSeastar.cmake to * detect the preconfigured Seastar builds, and * extract the build options from .pc files * expose library targets to be consumed by parent project - add Seastar as an external project, so we can build it from the parent project. BUILD_AWAYS is set to ensure that Seastar is rebuilt, as scylla developers are expected to modify Seastar occasionally. since the change in Seastar's SOURCE_DIR is not detectable via the ExternalProject, we have to rebuild it. this is atypical compared to standard ExternalProject usage: - Seastar's build system should already be configured at this point. - We maintain separate project variants for each configuration type. Benefits of this approach: - Allows the parent project to consume the compile options exposed by .pc file. as the compile options vary from one config to another. - Allows application of config-specific settings - Enables building Seastar within the parent project's build system - Facilitates linking of artifacts with the external project target, establishing proper dependencies between them - preserve the existing machinery of including Seastar only when building without multi-config generator. this allows users who don't use mult-config generator to build Seastar in-the-tree. the typical use case is the CI workflows performing the static analysis. we will update `configure.py` to merge the compilation database of scylla and seastar. Refs scylladb/scylladb#2717 Signed-off-by: Kefu Chai <kefu.chai@scylladb.com>
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.