32fff17e19
`scylla-sstable` currently has two ways to obtain the schema:
* via a `schema.cql` file.
* load schema definition from memory (only works for system tables).
This meant that for most cases it was necessary to export the schema into a `CQL` format and write it to a file. This is very flexible. The sstable can be inspected anywhere, it doesn't have to be on the same host where it originates form. Yet in many cases the sstable *is* inspected on the same host where it originates from. In this cases, the schema is readily available in the schema tables on disk and it is plain annoying to have to export it into a file, just to quickly inspect an sstable file.
This series solves this annoyance by providing a mechanism to load schemas from the on-disk schema tables. Furthermore, an auto-detect mechanism is provided to detect the location of these schema tables based on the path of the sstable, but if that fails, the tool check the usual locations of the scylla data dir, the scylla confguration file and even looks for environment variables that tell the location of these. The old methods are still supported. In fact, if a `schema.cql` is present in the working directory of the tool, it is preferred over any other method, allowing for an easy force-override.
If the auto-detection magic fails, an error is printed to the console, advising the user to turn on debug level logging to see what went wrong.
A comprehensive test is added which checks all the different schema loading mechanisms. The documentation is also updated to reflect the changes.
This change breaks the backward-compatibility of the command-line API of the tool, as `--system-schema` is now just a flag, the keyspace and table names are supplied separately via the new `--keyspace` and `--table` options. I don't think this will break anybody's workflow as this tools is still lightly used, exactly because of the annoying way the schema has to be provided. Hopefully after this series, this will change.
Example:
```
$ ./build/dev/scylla sstable dump-data /var/lib/scylla/data/ks/tbl2-d55ba230b9a811ed9ae8495671e9e4f8/quarantine/me-1-big-Data.db
{"sstables":{"/var/lib/scylla/data/ks/tbl2-d55ba230b9a811ed9ae8495671e9e4f8/quarantine//me-1-big-Data.db":[{"key":{"token":"-3485513579396041028","raw":"000400000000","value":"0"},"clustering_elements":[{"type":"clustering-row","key":{"raw":"","value":""},"marker":{"timestamp":1677837047297728},"columns":{"v":{"is_live":true,"type":"regular","timestamp":1677837047297728,"value":"0"}}}]}]}}
```
As seen above, subdirectories like `qurantine`, `staging` etc are also supported.
Fixes: https://github.com/scylladb/scylladb/issues/10126
Closes #13075
* github.com:scylladb/scylladb:
docs/operating-scylla/admin-tools: scylla-sstable.rst: update schema section
test/cql-pytest: test_tools.py: add test for schema loading
test/cql-pytest: nodetool.py: add flush_keyspace()
tools/scylla-sstable: reform schema loading mechanism
tools/schema_loader: add load_schema_from_schema_tables()
db/schema_tables: expose types schema
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.