f488eaebaf
Merged patch set by Botond Dénes: The view update generation process creates two readers. One is used to read the staging sstables, the data which needs view updates to be generated for, and another reader for each processed mutation, which reads the current value (pre-image) of each row in said mutation. The staging reader is created first and is kept alive until all staging data is processed. The pre-image reader is created separately for each processed mutation. The staging reader is not restricted, meaning it does not wait for admission on the relevant reader concurrency semaphore, but it does register its resource usage on it. The pre-image reader however *is* restricted. This creates a situation, where the staging reader possibly consumes all resources from the semaphore, leaving none for the later created pre-image reader, which will not be able to start reading. This will block the view building process meaning that the staging reader will not be destroyed, causing a deadlock. This patch solves this by making the staging reader restricted and making it evictable. To prevent thrashing -- evicting the staging reader after reading only a really small partition -- we only make the staging reader evictable after we have read at least 1MB worth of data from it. test/boost: view_build_test: add test_view_update_generator_buffering test/boost: view_build_test: add test test_view_update_generator_deadlock reader_permit: reader_resources: add operator- and operator+ reader_concurrency_semaphore: add initial_resources() test: cql_test_env: allow overriding database_config mutation_reader: expose new_reader_base_cost db/view: view_updating_consumer: allow passing custom update pusher db/view: view_update_generator: make staging reader evictable db/view: view_updating_consumer: move implementation from table.cc to view.cc database: add make_restricted_range_sstable_reader() Signed-off-by: Botond Dénes <bdenes@scylladb.com> --- db/view/view_updating_consumer.hh | 51 ++++++++++++++++++++++++++++--- db/view/view.cc | 39 +++++++++++++++++------ db/view/view_update_generator.cc | 19 +++++++++--- 3 files changed, 91 insertions(+), 18 deletions(-)
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.
- Packaging documentation on how to build Scylla packages for different Linux distributions.
- 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 in ./docs and on the wiki. There is currently no clear definition of what goes where, so when looking for something be sure to check both. 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 users mailing list 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.