0fd1050784
Adds glue needed to pass lz4 and zstd with streaming and/or dictionaries as the network traffic compressors for Seastar's RPC servers. The main jobs of this glue are: 1. Implementing the API expected by Seastar from RPC compressors. 2. Expose metrics about the effectiveness of the compression. 3. Allow dynamically switching algorithms and dictionaries on a running connection, without any extra waits. The biggest design decision here is that the choice of algorithm and dictionary is negotiated by both sides of the connection, not dictated unilaterally by the sender. The negotiation algorithm is fairly complicated (a TLA+ model validating it is included in the commit). Unilateral compression choice would be much simpler. However, negotiation avoids re-sending the same dictionary over every connection in the cluster after dictionary updates (with one-way communication, it's the only reliable way to ensure that our receiver possesses the dictionary we are about to start using), lets receivers ask for a cheaper compression mode if they want, and lets them refuse to update a dictionary if they don't think they have enough free memory for that. In hindsight, those properties probably weren't worth the extra complexity and extra development effort. Zstd can be quite expensive, so this patch also includes a mechanism which temporarily downgrades the compressor from zstd to lz4 if zstd has been using too much CPU in a given slice of time. But it should be noted that this can't be treated as a reliable "protection" from negative performance effects of zstd, since a downgrade can happen on the sender side, and receivers are at the mercy of senders.
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
-
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.