72bbe75d5b
This PR fixes a problem with replacing a node with tablets when RF=N. Currently, this will fail because tablet replica allocation for rebuild will not be able to find a viable destination, as the replacing node is not considered to be a candidate. It cannot be a candidate because replace rolls back on failure and we cannot roll back after tablets were migrated. The solution taken here is to not drain tablet replicas from replaced node during topology request but leave it to happen later after the replaced node is in left state and replacing node is in normal state. The replacing node waits for this draining to be complete on boot before the node is considered booted. Fixes https://github.com/scylladb/scylladb/issues/17025 Nodes in the left state will be kept in tablet replica sets for a while after node replace is done, until the new replica is rebuilt. So we need to know about those node's location (dc, rack) for two reasons: 1) algorithms which work with replica sets filter nodes based on their location. For example materialized views code which pairs base replicas with view replicas filters by datacenter first. 2) tablet scheduler needs to identify each node's location in order to make decisions about new replica placement. It's ok to not know the IP, and we don't keep it. Those nodes will not be present in the IP-based replica sets, e.g. those returned by get_natural_endpoints(), only in host_id-based replica sets. storage_proxy request coordination is not affected. Nodes in the left state are still not present in token ring, and not considered to be members of the ring (datacanter endpoints excludes them). In the future we could make the change even more transparent by only loading locator::node* for those nodes and keeping node* in tablet replica sets. Currently left nodes are never removed from topology, so will accumulate in memory. We could garbage-collect them from topology coordinator if a left node is absent in any replica set. That means we need a new state - left_for_real. Closes scylladb/scylladb#17388 * github.com:scylladb/scylladb: test: py: Add test for view replica pairing after replace raft, api: Add RESTful API to query current leader of a raft group test: test_tablets_removenode: Verify replacing when there is no spare node doc: topology-on-raft: Document replace behavior with tablets tablets, raft topology: Rebuild tablets after replacing node is normal tablets: load_balancer: Access node attributes via node struct tablets: load_balancer: Extract ensure_node() mv: Switch to using host_id-based replica set effective_replication_map: Introduce host_id-based get_replicas() raft topology: Keep nodes in the left state to topology tablets: Introduce read_required_hosts()
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 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
- Follow the ScyllaDB Style Guide.
- 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.
Creating Knowledge Base Articles
The kb/ directory holds source files for knowledge base articles in the Knowledge Base section of the ScyllaDB documentation.
The kb/kb_common subdirectory contains a template for knowledge base articles to help you create new articles.
To create a new knowledge base article (KB):
- Copy the
kb-article-template.rstfile from/kb/kb_commonto/kband rename it with a unique name. - Open the new file and fill in the required information.
- Remove what is not needed.
- Run
make previewto build the docs and preview them locally. - Send a PR with "KB" in its title.
Building User Documentation
Prerequisites
- Python 3. Check your version with
$ python --version. - poetry 1.12 or later
- make
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.