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This is a forward port (from scylla-enterprise) of additional compression options (zstd, dictionaries shared across messages) for inter-node network traffic. It works as follows: After the patch, messaging_service (Scylla's interface for all inter-node communication) compresses its network traffic with compressors managed by the new advanced_rpc_compression::tracker. Those compressors compress with lz4, but can also be configured to use zstd as long as a CPU usage limit isn't crossed. A precomputed compression dictionary can be fed to the tracker. Each connection handled by the tracker will then start a negotiation with the other end to switch to this dictionary, and when it succeeds, the connection will start being compressed using that dictionary. All traffic going through the tracker is passed as a single merged "stream" through dict_sampler. dictionary_service has access to the dict_sampler. On chosen nodes (in the "usual" configuration: the Raft leader), it uses the sampler to maintain a random multi-megabyte sample of the sampler's stream. Every several minutes, it copies the sample, trains a compression dictionary on it (by calling zstd's training library via the alien_worker thread) and publishes the new dictionary to system.dicts via Raft's write_mutation command. This update triggers (eventually) a callback on all nodes, which feeds the new dictionary to advanced_rpc_compression::tracker, and this switches (eventually) all inter-node connections to this dictionary. Closes scylladb/scylladb#22032 * github.com:scylladb/scylladb: messaging_service: use advanced_rpc_compression::tracker for compression message/dictionary_service: introduce dictionary_service service: make Raft group 0 aware of system.dicts db/system_keyspace: add system.dicts utils: add advanced_rpc_compressor utils: add dict_trainer utils: introduce reservoir_sampling utils: introduce alien_worker utils: add stream_compressor
ScyllaDB Documentation
This repository contains the source files for ScyllaDB Open Source documentation.
- The
devfolder contains developer-oriented documentation related to the ScyllaDB code base. It is not published and is only available via GitHub. - All other folders and files contain user-oriented documentation related to ScyllaDB Open Source and are sources for opensource.docs.scylladb.com.
To report a documentation bug or suggest an improvement, open an issue in GitHub issues for this project.
To contribute to the documentation, open a GitHub pull request.
Key Guidelines for Contributors
- The user documentation is written in reStructuredText (RST) - a plaintext markup language similar to Markdown. If you're not familiar with RST, see ScyllaDB RST Examples.
- The developer documentation is written in Markdown. See Basic Markdown Syntax for reference.
- Follow the ScyllaDB Style Guide.
To prevent the build from failing:
-
If you add a new file, ensure it's added to an appropriate toctree, for example:
.. toctree:: :maxdepth: 2 :hidden: Page X </folder1/article1> Page Y </folder1/article2> Your New Page </folder1/your-new-article> -
Make sure the link syntax is correct. See the guidelines on creating links
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Make sure the section headings are correct. See the guidelines on creating headings Note that the markup must be at least as long as the text in the heading. For example:
---------------------- Prerequisites ----------------------
Building User Documentation
Prerequisites
- Python
- poetry
- make
See the ScyllaDB Sphinx Theme prerequisites to check which versions of the above are currently required.
Mac OS X
You must have a working Homebrew in order to install the needed tools.
You also need the standard utility make.
Check if you have these two items with the following commands:
brew help
make -h
Linux Distributions
Building the user docs should work out of the box on most Linux distributions.
Windows
Use "Bash on Ubuntu on Windows" for the same tools and capabilities as on Linux distributions.
Building the Docs
- Run
make previewto build the documentation. - Preview the built documentation locally at http://127.0.0.1:5500/.
Cleanup
You can clean up all the build products and auto-installed Python stuff with:
make pristine
Information for Contributors
If you are interested in contributing to Scylla docs, please read the Scylla open source page at http://www.scylladb.com/opensource/ and complete a Scylla contributor agreement if needed. We can only accept documentation pull requests if we have a contributor agreement on file for you.
Third-party Documentation
-
Do any copying as a separate commit. Always commit an unmodified version first and then do any editing in a separate commit.
-
We already have a copy of the Apache license in our tree, so you do not need to commit a copy of the license.
-
Include the copyright header from the source file in the edited version. If you are copying an Apache Cassandra document with no copyright header, use:
This document includes material from Apache Cassandra.
Apache Cassandra is Copyright 2009-2014 The Apache Software Foundation.