022add117e
The test test/cluster/test_ttl_row.py::test_row_ttl_scheduling_group wants to verify that the new CQL per-row TTL feature does all its work (expiration scanning, deletion of expired items) on all nodes in the "streaming" scheduling group, not in the statement scheduling group. As originally written, the test couldn't require that it uses exactly zero time in the statement scheduling group - because some things do happen there - specifically the ALTER TABLE request we use to enable TTL. So the test checked that the time in the "wrong" group is less than 0.2 of the total time, not zero. But in one CI run, we got to exactly 0.2 and the test failed. Running this test locally, I see the margin is pretty narrow: The test almost always fails if I set the threshold ratio to 0.1. The solution in this patch is to move the ALTER TABLE work to a different scheduling group (by using an additional service level). After doing that the CPU usage in sl:default goes down to exactly zero - not close to zero but exactly zero. However, it seems that there is always some rare background work in sl:default and debug builds it can come out more than 0ms (e.g., in one test we saw 1ms), so we keep checking that sl:default is much lower than sl:stream - not exactly zero. Incidentally, I converted the serial loop adding the 200 rows in the test's setup to a parallel loop, to make the test setup slightly faster. I also added to the test a sanity check that the scheduling group sl:default that we are measuring that TTL does zero work in, is actually the scheduling group that normal writes work in (to avoid the risk of having a test that verifies that some irrelevant scheduling group is unsurprisingly getting zero usage...). Fixes SCYLLADB-1495. Closes scylladb/scylladb#29447
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.