200bc82913
In commit acfa180766 we added to
test/cql-pytest a mechanism to detect when Scylla crashes in the middle
of a test function - in which case we report the culprit test and exit
immediately to avoid having a hundred more tests report that they failed
as well just because Scylla was down.
However, if Scylla was *never* up - e.g., if the user ran "pytest" without
ever running Scylla - we still report hundreds of tests as having failed,
which is confusing and not helpful.
So with this patch, if a connection cannot be made to Scylla at all,
the test exits immediately, explaining what went wrong, not blaming
any specific test:
$ pytest
...
! _pytest.outcomes.Exit: Cannot connect to Scylla at --host=localhost --port=9042 !
============================ no tests ran in 0.55s =============================
Beyond being a helpful reminder for a developer who runs "pytest" without
having started Scylla first (or using test/cql-pytest/run or test.py to
start Scylla easily), this patch is also important when running tests
through test.py if it reuses an instance of Scylla that crashed during an
earlier pytest file's run.
This patch does not fix test.py - it can still try to run pytest with
a dead Scylla server without checking. But at least with this patch
pytest will notice this problem immediately and won't report hundreds of
test functions having failed. The only report the user will see will be
the last test which crashed Scylla, which will make it easier to find
this failure without being hidden between hundreds of spurious failures.
Fixes #12360
Signed-off-by: Nadav Har'El <nyh@scylladb.com>
Closes #12401
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.