14cdd034ee
The test test_scan.py::test_scan_long_partition_tombstone_string checks that a full-table Scan operation ends a page in the middle of a very long string of partition tombstones, and does NOT scan the entire table in one page (if we did that, getting a single page could take an unbounded amount of time). The test is currently flaky, having failed in CI runs three times in the past two months. The reason for the flakiness is that we don't know exactly how long we need to make the sequence of partition tombstones in the test before we can be absolutely sure a single page will not read this entire sequence. For single-partition scans we have the "query_tombstone_page_limit" configuration parameter, which tells us exactly how long we need to make the sequence of row tombstones. But for a full-table scan of partition tombstones, the situation is more complicated - because the scan is done in parallel on several vnodes in parallel and each of them needs to read query_tombstone_page_limit before it stops. In my experiments, using query_tombstone_limit * 4 consecutive tombstones was always enough - I ran this test hundreds of times and it didn't fail once. But since it did fail on Jenkins very rarely (3 times in the last two months), maybe the multiplier 4 isn't enough. So this patch doubles it to 8. Hopefully this would be enough for anyone (TM). This makes this test even bigger and slower than it was. To make it faster, I changed this test's write isolation mode from the default always_use_lwt to forbid_rmw (not use LWT). This leaves the test's total run time to be similar to what it was before this patch - around 0.5 seconds in dev build mode on my laptop. Fixes #12817 Signed-off-by: Nadav Har'El <nyh@scylladb.com> Closes #12819
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.
- 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 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 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 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.