edfb89ef65
When a table is dropped, we delete its sstables, and finally try to delete the table's top-level directory with the rmdir system call. When the auto-snapshot feature is enabled (this is still Scylla's default), the snapshot will remain in that directory so it won't be empty and will cannot be removed. Today, this results in a long, ugly and scary warning in the log: ``` WARN 2023-07-06 20:48:04,995 [shard 0] sstable - Could not remove table directory "/tmp/scylla-test-198265/data/alternator_alternator_Test_1688665684546/alternator_Test_1688665684546-4238f2201c2511eeb15859c589d9be4d/snapshots": std::filesystem::__cxx11::filesystem_error (error system:39, filesystem error: remove failed: Directory not empty [/tmp/scylla-test-198265/data/alternator_alternator_Test_1688665684546/alternator_Test_1688665684546-4238f2201c2511eeb15859c589d9be4d/snapshots]). Ignored. ``` It is bad to log as a warning something which is completely normal - it happens every time a table is dropped with the perfectly valid (and even default) auto-snapshot mode. We should only log a warning if the deletion failed because of some unexpected reason. And in fact, this is exactly what the code **tried** to do - it does not log a warning if the rmdir failed with EEXIST. It even had a comment saying why it was doing this. But the problem is that in Linux, deleting a non-empty directory does not return EEXIST, it returns ENOTEMPTY... Posix actually allows both. So we need to check both, and this is the only change in this patch. To confirm this that this patch works, edit test/cql-pytest/run.py and change auto-snapshot from 0 to 1, run test/alternator/run (for example) and see many "Directory not empty" warnings as above. With this patch, none of these warnings appear. Fixes #13538 Signed-off-by: Nadav Har'El <nyh@scylladb.com> Closes #14557
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 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.